A wind power generation grid-connected cascade converter system

Abstract

The present application provides a wind power generation grid-connected cascade converter system, which includes: a generator, a converter group, and a transformer, wherein the output end of the generator is connected to the input end of the converter group, and the output end of the converter group is connected to the input end of the transformer; wherein the converter group includes a first converter, a second converter, and a third converter connected in a cascade manner, wherein the first converter is connected to the second converter and the third converter respectively, and the second converter is connected to the third converter. The present application can achieve an increase in the output power of the wind generator set and an increase in the voltage level of the converter group output voltage by adopting a new converter group with an AC cascade topology. At the same time, the wind power generation grid-connected cascade converter system can achieve self-balancing of the output power, effectively improve the grid-connected performance of the wind generator set, and improve the overall performance of the wind power generation grid-connected cascade converter system.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a wind power generation grid-connected cascade converter system. Background Art

[0002] Wind turbines are now widely used in power generation, and their power levels are gradually increasing. However, as wind turbine power levels increase, the grid-connected voltage level of wind power converters remains at 690VAC, which can lead to increasing grid-connected currents.

[0003] In related technologies, the grid connection of high-power wind turbines typically involves operating two 690VAC wind turbine converters in parallel. However, this approach often results in numerous grid-connected cables, poor maintainability, high grid-connected currents, and significantly increased line losses. Furthermore, the parallel connection of multiple turbines is more prone to circulating currents. Failure to effectively suppress circulating currents in the turbines can significantly increase operating losses and reduce turbine efficiency.

[0004] Therefore, how to simplify the wiring method, improve maintainability, reduce operating losses, and improve unit operating efficiency while ensuring the reliability of the wind power grid-connected cascade conversion system has become an urgent problem to be solved. Summary of the Invention

[0005] The present application provides a wind power generation grid-connected cascade converter system, which is used to simplify the wiring method, improve maintainability, reduce operating losses, and improve the operating efficiency of the unit on the basis of ensuring the reliability of the wind power generation grid-connected cascade converter system.

[0006] According to the first aspect of the present application, a wind power generation grid-connected cascade conversion system is provided, comprising: a generator, a converter group and a transformer, wherein the output end of the generator is connected to the input end of the converter group, and the output end of the converter group is connected to the input end of the transformer; wherein the converter group comprises a first converter, a second converter and a third converter connected in a cascade manner, the first converter is respectively connected to the second converter and the third converter, and the second converter is connected to the third converter.

[0007] In addition, the wind power grid-connected cascade converter system according to the above embodiment of the present application may also have the following additional technical features:

[0008] According to one embodiment of the present application, the output end of the generator is a nine-phase three-winding output end; wherein, the input end of the first converter is connected to the first winding output end of the generator, the input end of the second converter is connected to the second winding output end of the generator, and the input end of the third converter is connected to the third winding output end of the generator.

[0009] According to one embodiment of the present application, the generator is a three-winding nine-phase synchronous generator, and the generator is a three-winding nine-phase synchronous generator. The first winding output end of the generator, the second winding output end of the generator, and the third winding output end of the generator are all three-phase output ends.

[0010] According to one embodiment of the present application, it also includes: a first reactor group, the first reactor group includes a first machine-side reactor and a first grid-side reactor, the generator is connected to the first converter through the first machine-side reactor, and the transformer is connected to the first converter through the first grid-side reactor; a second reactor group, the second reactor group includes a second machine-side reactor and a second grid-side reactor, the generator is connected to the second converter through the second machine-side reactor, and the transformer is connected to the second converter through the second grid-side reactor; a third reactor group, the third reactor group includes a third machine-side reactor and a third grid-side reactor, the generator is connected to the third converter through the third machine-side reactor, and the transformer is connected to the third converter through the third grid-side reactor.

[0011] According to one embodiment of the present application, the output end of the first converter, the output end of the second converter and the output end of the third converter are all three-phase output ends; wherein, the first output end of the first converter is connected to the first output end of the second converter, the second output end of the first converter is connected to the first output end of the third converter; and the second output end of the second converter is connected to the second output end of the third converter.

[0012] According to one embodiment of the present application, the first converter, the second converter, and the third converter are all three-phase full-bridge converters.

[0013] According to one embodiment of the present application, the machine-side rectifier unit of any one of the first converter, the second converter and the third converter is a fully-controlled rectifier unit or an uncontrolled rectifier unit, and the grid-side inverter unit is a fully-controlled inverter unit.

[0014] According to an embodiment of the present application, the first converter, the second converter, and the third converter are all target level converters.

[0015] According to an embodiment of the present application, the target-level converter is a two-level converter or a three-level converter.

[0016] According to one embodiment of the present application, the input end of the transformer is a three-phase input end; wherein, the third output end of the first converter is connected to the first input end of the transformer, the third output end of the second converter is connected to the second input end of the transformer, and the third output end of the third converter is connected to the third input end of the transformer.

[0017] According to one embodiment of the present application, it further includes: a wind wheel group of the unit, the wind wheel group of the unit includes at least one wind wheel, and each of the wind wheel is connected to the generator.

[0018] The technical solutions provided by the embodiments of the present application include at least the following beneficial effects:

[0019] This application provides a wind power grid-connected cascade converter system that, by employing a novel converter group with an AC cascade topology, can increase the output power of the wind turbine generator set and the voltage level of the converter group's output voltage. Furthermore, the wind power grid-connected cascade converter system can achieve self-balancing of output power, effectively improving the grid-connected performance of the wind turbine generator set and enhancing the overall performance of the wind power grid-connected cascade converter system.

[0020] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are provided to facilitate a better understanding of the present invention and do not constitute a limitation of the present application.

[0022] Figure 1 A schematic diagram of a wind power grid-connected cascade converter system provided in an embodiment of the present application;

[0023] Figure 2 A schematic diagram of another wind power grid-connected cascade converter system provided in an embodiment of the present application;

[0024] Figure 3 A schematic diagram of another wind power grid-connected cascade converter system provided in an embodiment of the present application;

[0025] Figure 4 A schematic diagram of another wind power grid-connected cascade converter system provided in an embodiment of the present application;

[0026] Figure 5 A schematic diagram of the internal topology of a converter provided in an embodiment of the present application;

[0027] Figure 6 A schematic diagram of the internal topology of another converter provided in an embodiment of the present application;

[0028] Figure 7 A schematic diagram of another wind power grid-connected cascade converter system provided in an embodiment of the present application;

[0029] Figure 8 A schematic diagram of another wind power grid-connected cascade converter system provided in an embodiment of the present application;

[0030] Figure 9 A schematic diagram of another wind power grid-connected cascade converter system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The following description of exemplary embodiments of the present application is made in conjunction with the accompanying drawings, including various details of the embodiments of the present application to facilitate understanding. These details should be considered as merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description.

[0032] The wind power generation grid-connected cascade converter system of the present application is described in detail below using embodiments.

[0033] Figure 1 Schematic diagram of a wind power grid-connected cascade converter system provided in an embodiment of the present application.

[0034] like Figure 1 As shown, the wind power grid-connected cascade conversion system 1000 proposed in this embodiment includes: a generator 100, a converter group 200 and a transformer 300, the output end of the generator 100 is connected to the input end of the converter group 200, and the output end of the converter group 200 is connected to the input end of the transformer 300.

[0035] The converter group 200 includes a first converter 10, a second converter 20 and a third converter 30 connected in a cascade manner. The first converter 10 is connected to the second converter 20 and the third converter 30 respectively, and the second converter 20 is connected to the third converter 30.

[0036] In the embodiment of the present application, after the electric energy is input to the input end of the converter group 200 through the output end of the generator 100, the converter group 200 can perform current conversion and input the converted electric energy to the input end of the transformer 300 through the output end of the converter group 200.

[0037] The transformer 300 may be a step-up transformer for stepping up the converted electric energy.

[0038] Therefore, this application proposes a wind power grid-connected cascade converter system 1000, which can achieve an increase in the output power of a wind turbine generator set and an increase in the voltage level of the converter set output voltage by adopting a new converter set with an AC cascade topology. At the same time, the wind power grid-connected cascade converter system can achieve self-balancing of output power, effectively improving the grid-connected performance of the wind turbine generator set and enhancing the overall performance of the wind power grid-connected cascade converter system.

[0039] In some embodiments, as Figure 2 As shown, the output end of the generator 100 is a nine-phase three-winding output end.

[0040] In the embodiment of the present application, the output end of the generator 100 includes a first winding output end 101, a second winding output end 102, and a third winding output end 103. In this case, the input end of the first converter 10 is connected to the first winding output end 101 of the generator 200, the input end of the second converter 20 is connected to the second winding output end 102 of the generator 100, and the input end of the third converter 30 is connected to the third winding output end 103 of the generator 100.

[0041] It should be noted that the specific selection of the generator is not limited in this application and can be set according to actual conditions.

[0042] As a possible implementation, the generator 100 is a three-winding nine-phase synchronous generator, and the first winding output end 101 of the generator 100, the second winding output end 102 of the generator 100, and the third winding output end 103 of the generator 100 are all three-phase output ends.

[0043] In some embodiments, as Figure 3 As shown, the wind power generation grid-connected cascade converter system 1000 proposed in this embodiment further includes: a first reactor group 400 , a second reactor group 500 and a third reactor group 600 .

[0044] The first reactor group 400 includes a first generator-side reactor 401 and a first grid-side reactor 402 . The generator 100 is connected to the first converter 10 via the first generator-side reactor 401 , and the transformer 300 is connected to the first converter 10 via the first grid-side reactor 402 .

[0045] The second reactor group 500 includes a second generator-side reactor 501 and a second grid-side reactor 502 . The generator 100 is connected to the second converter 20 via the second generator-side reactor 501 , and the transformer 300 is connected to the second converter 20 via the second grid-side reactor 502 .

[0046] The third reactor group 600 includes a third generator-side reactor 601 and a third grid-side reactor 602 . The generator 100 is connected to the third converter 30 via the third generator-side reactor 601 , and the transformer 300 is connected to the third converter 30 via the third grid-side reactor 602 .

[0047] In some embodiments, the first converter 10 , the second converter 20 , and the third converter 30 are all three-phase full-bridge converters, and the output ends of the first converter 10 , the second converter 20 , and the third converter 30 are all three-phase output ends.

[0048] In some embodiments, the machine-side rectifier unit of any one of the first converter 10 , the second converter 20 , and the third converter 30 is a fully-controlled rectifier unit or an uncontrolled rectifier unit, and the grid-side inverter unit is a fully-controlled inverter unit.

[0049] like Figure 4 As shown, the output end of the first converter 10 includes a first output end a1, a second output end b1 and a third output end c1; the output end of the second converter 20 includes a first output end a2, a second output end b2 and a third output end c2; the output end of the third converter 30 includes a first output end a3, a second output end b3 and a third output end c3.

[0050] Among them, the first output end a1 of the first converter 10 is connected to the first output end a2 of the second converter 20, the second output end b1 of the first converter 10 is connected to the first output end a3 of the third converter 30; the second output end b2 of the second converter 20 is connected to the second output end b3 of the third converter 30.

[0051] It should be noted that the present application does not limit the specific selection of the first converter, the second converter and the third converter, and they can be set according to actual conditions.

[0052] As a possible implementation, it may be set that the first converter 10 , the second converter 20 , and the third converter 30 all use target level converters.

[0053] The target level converter may be a two-level converter or a three-level converter.

[0054] Optionally, the first converter 10, the second converter 20 and the third converter 30 are all two-level converters. In this case, the internal topology of the first converter 10, the second converter 20 and the third converter is as follows: Figure 5 In this case, the number of internal components of the converter is small and the control is relatively simple, but the voltage utilization is low, the harmonic content is high, the corresponding waveform is poor, and the switching frequency is high.

[0055] Optionally, the first converter 10, the second converter 20 and the third converter 30 are all three-level converters. In this case, the internal topology of the first converter 10, the second converter 20 and the third converter is as follows: Figure 6 In this case, the converter has a large number of internal components and the control is relatively complex, but the voltage utilization is high, the harmonic content is low, the corresponding waveform is better, and the switching frequency is low.

[0056] It should be noted that the specific selection of the target level converter is not limited in this application and can be determined according to actual conditions.

[0057] As another possible implementation, the first converter 10, the second converter 20, and the third converter 30 may be configured to use converters with different target levels. For example, the first converter 10 may use a two-level converter, and the second converter 20 and the third converter 30 may both use a three-level converter. For another example, the first converter 10 and the second converter 20 may use a three-level converter, and the third converter 30 may both use a two-level converter.

[0058] In some embodiments, as Figure 7 As shown, the input end of the transformer 300 is a three-phase input end.

[0059] Among them, the third output terminal c1 of the first converter 10 is connected to the first input terminal A of the transformer 100, the third output terminal c2 of the second converter 20 is connected to the second input terminal B of the transformer 100, and the third output terminal c3 of the third converter 30 is connected to the third input terminal C of the transformer 100.

[0060] In some embodiments, as Figure 8 As shown, the wind power generation grid-connected cascade converter system 1000 proposed in this application further includes: a wind turbine rotor assembly 700 .

[0061] The wind wheel assembly 700 of the unit includes at least one wind wheel, and each wind wheel is connected to the generator 100 .

[0062] In summary, in the wind power grid-connected cascade converter system 1000 proposed in this application, the input end of the converter group 200 is connected to the output end of the three-winding nine-phase synchronous generator 100 of the wind turbine group through the machine-side reactor.

[0063] The converter group 200 is composed of a single basic three-phase full-bridge converter; the input end of the first converter 10 is connected to the output end 101 of the first set of windings of the generator 100; the input end of the second converter 20 is connected to the output end 102 of the second set of windings of the generator 200; and the input end of the third converter 30 is connected to the output end 103 of the third set of windings of the generator 100.

[0064] Among them, the output ends of the three converters are connected in a cascade manner, that is, the a1 phase of the first converter 10 is connected to the A phase of the transformer (grid-connected transformer) 300, the a2 phase of the second converter 20 is connected to the B phase of the grid-connected transformer 300, and the a3 phase of the third converter 30 is connected to the C phase of the grid-connected transformer 300.

[0065] That is, phase b1 of the first converter 10 is connected to phase a2 of the second converter 20 , phase c1 of the first converter 10 is connected to phase a3 of the third converter 30 , and phase c2 of the second converter 20 is connected to phase b3 of the third converter 30 .

[0066] The following explains the parameter changes of the current transformer group in the wind power grid-connected cascade converter system.

[0067] In the related art, a basic converter or a converter group composed of basic converters is used, the output line voltage is U, and the phase current is I. In this case, the output power of the wind turbine is P=1.732*U*I.

[0068] Different from the related art, in this application, Figure 9 As shown, the converter group composed of converters (grid-connected converters) with a cascaded topology can increase the output line voltage to 2U and the phase current to 1.5I. In this case, the output power of the wind turbine is P = 1.732*2*U*1.5*I, which is three times the output power of the wind turbine group composed of converters with basic converters.

[0069] Therefore, the wind power grid-connected cascade conversion system proposed in this application adopts a three-winding nine-phase permanent magnet synchronous generator, and the output end of the generator is connected to the machine-side input end of three sets of basic converter units. The converter adopts a new AC cascade topology structure, and the AC cascade method can achieve an output of 2 times the output voltage of the basic converter, and the voltage level can reach 1140~3300V. The output power is 3 times the output power when the basic converter is used in the related technology, and the converter system can achieve self-balancing of the output power, effectively improving the grid-connected performance of the current wind turbine generator set.

[0070] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this application can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in this application can be achieved. This is not a limitation herein.

[0071] The above specific embodiments do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles disclosed in this application shall be included in the scope of protection of this application.

Claims

1. A wind power generation grid-connected cascade converter system, characterized in that: include: A generator, a converter group and a transformer, wherein the output end of the generator is connected to the input end of the converter group, and the output end of the converter group is connected to the input end of the transformer; wherein, The converter group includes a first converter, a second converter, and a third converter connected in a cascade manner, wherein the first converter is connected to the second converter and the third converter respectively, and the second converter is connected to the third converter; The output end of the first converter, the output end of the second converter and the output end of the third converter are all three-phase output ends; wherein, The second output end of the first converter is connected to the first output end of the second converter, the third output end of the first converter is connected to the first output end of the third converter; the third output end of the second converter is connected to the second output end of the third converter.

2. The wind power generation grid-connected cascade converter system according to claim 1, characterized in that: The output end of the generator is a nine-phase three-winding output end; wherein, The input end of the first converter is connected to the output end of the first winding of the generator, the input end of the second converter is connected to the output end of the second winding of the generator, and the input end of the third converter is connected to the output end of the third winding of the generator.

3. The wind power generation grid-connected cascade converter system according to claim 2, characterized in that: The generator is a three-winding nine-phase synchronous generator, and the first winding output end of the generator, the second winding output end of the generator, and the third winding output end of the generator are all three-phase output ends.

4. The wind power generation grid-connected cascade converter system according to claim 1, characterized in that: Also includes: a first reactor group, the first reactor group including a first generator-side reactor and a first grid-side reactor, the generator being connected to the first converter via the first generator-side reactor, and the transformer being connected to the first converter via the first grid-side reactor; a second reactor group, the second reactor group comprising a second generator-side reactor and a second grid-side reactor, the generator being connected to the second converter via the second generator-side reactor, and the transformer being connected to the second converter via the second grid-side reactor; The third reactor group includes a third machine-side reactor and a third grid-side reactor. The generator is connected to the third converter via the third machine-side reactor, and the transformer is connected to the third converter via the third grid-side reactor.

5. The wind power generation grid-connected cascade converter system according to claim 1, characterized in that: The first converter, the second converter, and the third converter are all three-phase full-bridge converters.

6. The wind power generation grid-connected cascade converter system according to claim 1, characterized in that: The machine-side rectifier unit of any one of the first converter, the second converter and the third converter is a fully-controlled rectifier unit or an uncontrolled rectifier unit, and the grid-side inverter unit is a fully-controlled inverter unit.

7. The wind power generation grid-connected cascade converter system according to claim 1 or 5, characterized in that: The first converter, the second converter, and the third converter are all target level converters.

8. The wind power generation grid-connected cascade converter system according to claim 7, characterized in that: The target level converter is a two-level converter or a three-level converter.

9. The wind power generation grid-connected cascade converter system according to claim 1, characterized in that: The input end of the transformer is a three-phase input end; wherein, The third output terminal of the first converter is connected to the first input terminal of the transformer, the third output terminal of the second converter is connected to the second input terminal of the transformer, and the third output terminal of the third converter is connected to the third input terminal of the transformer.

10. The wind power generation grid-connected cascade converter system according to claim 1, characterized in that: Also includes: The wind wheel group of the unit includes at least one wind wheel, and each wind wheel is connected to the generator.

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