Transformer-free high-voltage direct-hanging fan energy conversion system

Abstract

The invention discloses a transformer-free high-voltage direct-hanging fan energy conversion system. The fan energy conversion system comprises a wind driven generator, a modular cascade wind power converter, a filter and a power grid, the wind driven generator is driven by the wind wheel to rotate, mechanical energy is converted into electric energy, frequency conversion and voltage generation are completed after energy conversion of the modular cascade wind power converter, and the electric energy is directly fed into a power grid after filtering of the filter. Through the structural arrangement of the fan energy conversion system, the energy conversion requirement of a high-capacity wind turbine generator is met, and meanwhile the economical efficiency and reliability of the fan energy conversion system are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of wind power generation and electrical engineering, and in particular relates to a transformer-free high-voltage direct-mounted wind turbine energy conversion system. Background Art

[0002] With the shortage of traditional fossil energy and the prominent problem of environmental pollution, countries around the world are vigorously developing new energy. Wind energy, as a clean and efficient renewable energy, has been vigorously developed.

[0003] The installed capacity of wind power generation is increasing rapidly. As the competition in the wind power industry becomes increasingly fierce, it is necessary to continuously improve the economy of wind turbines. Currently, wind turbines are constantly developing in the direction of large-scale, and the power of wind turbine energy conversion systems is also increasing. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of the prior art and disclose a transformerless high-voltage direct-mounted wind turbine energy conversion system. Through the structural setting of the wind turbine energy conversion system of the present invention, the energy conversion requirements of large-capacity wind turbines are met while improving their economy and reliability.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A transformerless high-voltage direct-mounted wind turbine energy conversion system, the wind turbine energy conversion system comprising: a wind turbine generator, a modular cascade wind power converter, a filter and a power grid; the wind turbine generator is driven to rotate by a wind wheel to convert mechanical energy into electrical energy, and after energy conversion by the modular cascade wind power converter, frequency conversion and voltage generation are completed, and the electrical energy is directly fed into the power grid after filtering by the filter.

[0007] According to a preferred embodiment, a plurality of windings are provided in the generator, and the windings are insulated from each other.

[0008] According to a preferred embodiment, each set of windings of the generator is respectively connected to a power module of a wind power converter; the windings in the generator are divided into two types, one is a three-phase winding, and the other is a single winding.

[0009] According to a preferred embodiment, the number of winding sets of the wind generator is determined according to the number of power modules in the wind power converter.

[0010] According to a preferred embodiment, the modular cascade wind power converter is a three-phase converter composed of 3N+1 power modules.

[0011] According to a preferred embodiment, each phase of the modular cascade wind power converter is first connected in series by the output ends of N single-phase output power modules, and the three-phase power modules are then connected in series to the output ends of the three-phase output power modules respectively. After the power modules are connected, they are connected to the power grid through a filter.

[0012] According to a preferred embodiment, each power module in the modular cascade wind power converter consists of two stages: an AC-DC input stage and a DC-AC output stage. The input stages are respectively connected to the three-phase windings of the generator, and the output stages are connected in series with adjacent power modules. The two stages share a DC bus and are coupled through DC capacitors.

[0013] According to a preferred embodiment, according to different application scenarios, each power module in the modular cascade wind power converter can adopt different topological structures, and each level adopts a two-level or multi-level topological structure.

[0014] The aforementioned main scheme of the present invention and its further options can be freely combined to form multiple schemes, all of which are schemes that can be adopted and claimed for protection by the present invention. After understanding the scheme of the present invention, those skilled in the art can understand that there are multiple combinations based on the prior art and common knowledge, all of which are technical schemes to be protected by the present invention, and they are not exhaustively listed here.

[0015] Beneficial effects of the present invention:

[0016] (1) A single wind turbine can be directly connected to the high-voltage distribution network of the wind farm, eliminating the transformer on the wind turbine side and eliminating transformer losses, which is beneficial to improving the economy of the system;

[0017] (2) By adopting the cascade topology solution, the voltage on the grid side of the converter can be easily increased, the current can be reduced, thinner cables can be selected, the economy can be improved, and the twisted cable problem can be solved;

[0018] (3) The cascade topology can easily achieve high-power conversion and meet the large-capacity conversion requirements brought about by the large-scale unit.

[0019] (4) Both two-phase output power modules and three-phase output power modules are used. The three-phase output power module uses a set of three-phase winding input and outputs three-phase voltage and current, which can reduce the number of motor windings and reduce the complexity of the motor structure. On the other hand, the equivalent phase voltage of the three-phase output power module is different from the output voltage of the two-phase output power module, which is conducive to determining the appropriate number of power modules according to the grid-connected voltage, increasing the voltage utilization of the power module, and improving the economy of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the electrical system of the fan of the present invention.

[0021] Figure 2 It is a structural diagram of the fan energy conversion system of the present invention.

[0022] Figure 3 This is a single-phase output power module topology structure adopted in the embodiment of the present invention.

[0023] Figure 4 This is a three-phase output power module topology structure adopted in the embodiment of the present invention.

[0024] Figure 5 It is a structural diagram of the wind turbine energy conversion system used in Example 1 of the present invention.

[0025] Figure 6 It is a structural diagram of the wind turbine energy conversion system used in Example 2 of the present invention. DETAILED DESCRIPTION

[0026] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0027] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, and it can be the internal connection of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In addition, the present invention should be pointed out that, in the present invention, unless the specific structure, connection relationship, positional relationship, power source relationship, etc. are specifically written out, the structure, connection relationship, positional relationship, power source relationship, etc. involved in the present invention are all known by those skilled in the art on the basis of the prior art without creative work.

[0029] like Figure 1As shown, the present invention discloses a transformer-free high-voltage direct-mounted wind turbine energy conversion system, the wind turbine energy conversion system comprising: a wind turbine generator, a modular cascade wind power converter, a filter and a power grid. The electric energy generated by the wind turbine generator is converted by the modular cascade wind power converter, and the electric energy is directly fed into the power grid after being filtered by the filter.

[0030] As attached Figure 2 As shown, the generator adopts a multi-winding solution, and each winding is insulated from each other; each set of windings of the generator is connected to a power module of the wind power converter, and the windings are divided into two types, one is a common three-phase winding with a total number of 3N, and the other is a separate special winding R0.

[0031] The number of winding sets of the wind turbine is determined by the number of modules of the wind power converter. The cascade wind power converter is a three-phase converter, which consists of 3N+1 power modules. Each phase of the wind power converter is first connected in series by the output ends of N single-phase output power modules, and then the three-phase power modules are connected in series and then connected in series to the output ends of the three-phase output power module ABC0. After the power modules are connected, they are connected to the grid through the filter Lf.

[0032] Each power module consists of two stages: an AC-DC input stage and a DC-AC output stage. The input stage is connected to the three-phase windings of the generator, and the output stage is connected in series with the adjacent power module. The two stages share a DC bus and are coupled through DC capacitors.

[0033] Depending on the application, the power module can adopt different topologies. Each level can choose a two-level or multi-level topology, such as Figure 3 , 4 As shown, it should be noted that in order to achieve grid fault ride-through of the wind power converter, a low-throughput component can be added to the DC bus. The low-throughput component can be a crowbar component composed of a power switch and an energy dissipation resistor, or it can be an electric energy conversion device with energy storage.

[0034] In order to further illustrate the embodiments of the present invention, the following is described in conjunction with specific examples:

[0035] Example 1

[0036] The wind turbine is directly connected to the 10kV system. The generator is designed with 22 independent windings. The cascade converter uses 7 single-phase output power modules in series per phase, and then the three-phase module is connected to a three-phase output power module.

[0037] As attached Figure 5 The structure of the wind turbine energy conversion system in Example 1 is shown. The front stage of the single-phase output power module adopts a three-phase two-level topology structure, the rear stage adopts a two-level H-bridge structure, and the two-stage structure of the three-phase output power module adopts an NPC three-level topology structure;

[0038] Embodiment 1 The total number of generator windings is 22, including three groups of 21 common windings and 1 high-power winding. After the outputs of the 7 power modules of each phase are connected in series, one end is connected to the three-phase output power module ABC0, and the other end is connected to the 10kV power grid through the filter.

[0039] Example 2

[0040] The wind turbine is directly connected to the 35kV system. The generator is designed with 49 independent windings. The cascade converter uses 16 single-phase output power modules in series per phase, and then the three-phase modules are connected to a three-phase output power module.

[0041] As attached Figure 6 The structure of the wind turbine energy conversion system of Example 2 is shown. The front stage of the single-phase output power module adopts a three-phase NPC three-level topology structure, the rear stage adopts an NPC three-level H-bridge structure, and the two-stage structure of the three-phase output power module adopts an NPC three-level topology structure;

[0042] The total number of windings of the generator in Example 2 is 49, including three groups of 48 common windings and 1 high-power winding. After the 16 power module outputs of each phase are connected in series, one end is connected to the three-phase output power module ABC0, and the other end is connected to the 35kV power grid through the filter.

[0043] It can be seen from the above embodiments that in the technical solution of the present invention, a single wind turbine is directly connected to the high-voltage distribution network, which eliminates the transformer on the wind turbine side and eliminates transformer loss, which is beneficial to improving the economy of the system; by adopting the cascade topology solution, it is easy to increase the voltage on the grid side of the converter, reduce the current, and select thinner cables to improve the economy and solve the cable twisting problem; after adopting the cascade topology, it is very easy to achieve high-power conversion and meet the large-capacity conversion requirements brought by the large-scale unit. At the same time, two-phase output power modules and three-phase output power modules are adopted, in which the three-phase output power module adopts a set of three-phase winding input and outputs three-phase voltage and current, which can reduce the number of motor windings and reduce the complexity of the motor structure; on the other hand, the equivalent phase voltage of the three-phase output power module is different from the output voltage of the two-phase output power module, which is beneficial to determine the appropriate number of power modules according to the grid voltage, increase the voltage utilization rate of the power module, and improve the economy of the system.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A transformerless high-voltage direct-mounted fan energy conversion system, characterized in that: The wind turbine energy conversion system comprises: a wind turbine generator, a modular cascade wind power converter, a filter and a power grid; The wind turbine is driven by the wind rotor to convert mechanical energy into electrical energy. After energy conversion by the modular cascade wind power converter, frequency conversion and voltage generation are completed, and the electrical energy is directly fed into the power grid after filtering.

2. The wind turbine energy conversion system according to claim 1, characterized in that: A plurality of windings are arranged in the generator, and the windings are insulated from each other.

3. The wind turbine energy conversion system according to claim 2, characterized in that: Each set of windings of the generator is respectively connected to a power module of the wind power converter; The windings in the generator are divided into two types, one is a three-phase winding and the other is a single winding.

4. The wind turbine energy conversion system according to claim 3, characterized in that: The number of winding sets of the wind generator is determined according to the number of power modules in the wind power converter.

5. The wind turbine energy conversion system according to claim 3, characterized in that: The modular cascade wind power converter is a three-phase converter, which is composed of 3N+1 power modules.

6. The wind turbine energy conversion system according to claim 5, characterized in that: Each phase of the modular cascade wind power converter is first connected in series by the output ends of N single-phase output power modules, and the three-phase power modules are connected in series and then connected in series to the output ends of the three-phase output power modules respectively. After the power modules are connected, they are connected to the power grid through filters.

7. The wind turbine energy conversion system according to claim 6, characterized in that: Each power module in the modular cascade wind power converter consists of two stages: an AC-DC input stage and a DC-AC output stage. The input stages are connected to the three-phase windings of the generator respectively, the output stage is connected in series with the adjacent power module, the two stages share a DC bus and are coupled through DC capacitors.

8. The wind turbine energy conversion system according to claim 7, characterized in that: According to different application scenarios, each power module in the modular cascade wind power converter can adopt different topological structures, and each level adopts a two-level or multi-level topological structure.

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