Wind generating set

Abstract

The invention provides a wind generating set. The wind generating set comprises a generator; the primary side of the transformer is connected to the generator; the input end of the converter is connected to the secondary side of the transformer, the direct current bus voltage of the converter is larger than the machine side input voltage of the converter, and the machine side input voltage is smaller than the output line voltage of the generator. According to the wind generating set disclosed by the embodiment of the invention, the generator can be prevented from entering a deep flux weakening state.

Description

Technical Field

[0001] The present application relates to the field of wind power, and more specifically, to a wind turbine generator set. Background Art

[0002] The loads of wind turbines are becoming increasingly diversified. In addition to the current mainstream access to the grid, there are a variety of DC loads that can be connected to the load end of the wind turbine, and the DC bus voltage is also gradually increasing. Existing wind turbines cannot meet the needs of different DC loads.

[0003] In addition, due to the various voltage level requirements of DC loads, the DC bus voltage of the wind turbine converter has been increased to 1800 V. The rectifier module of the wind turbine generator set needs to be rectified at the input voltage level of the generator side, so the input voltage of the generator side is required to be around 1270 V (for example, 1250 V).

[0004] However, in this case, the generator will be in a deep magnetic weakening state, and the machine-side control system will be at risk of instability, which may cause the wind turbine to be disconnected from the grid at high speed, causing great harm to the unit. Summary of the invention

[0005] In order to solve at least one of the above technical problems, the present disclosure provides a wind turbine generator set.

[0006] One of the objectives of the present disclosure is to provide a wind turbine generator set capable of preventing the generator from entering a deep magnetic weakening state.

[0007] One of the objectives of the present disclosure is to provide a wind turbine generator set capable of adjusting a DC bus voltage to meet different DC load requirements.

[0008] One of the objectives of the present disclosure is to provide a wind turbine generator set capable of stabilizing the machine-side input voltage of a converter.

[0009] According to a first aspect of the present disclosure, a wind turbine generator set is provided, which includes: a generator; a transformer, wherein the primary side of the transformer is connected to the generator; and a converter, wherein the input end of the converter is connected to the secondary side of the transformer, wherein the DC bus voltage of the converter is greater than the machine-side input voltage of the converter, and the machine-side input voltage is less than the output line voltage of the generator.

[0010] According to an embodiment of the present disclosure, the difference between the machine-side input voltage and the output line voltage of the generator may be greater than or equal to 40V.

[0011] According to an embodiment of the present disclosure, the turns ratio of the transformer may be greater than or equal to 1.02.

[0012] According to an embodiment of the present disclosure, the transformer may be an autotransformer.

[0013] According to an embodiment of the present disclosure, the DC bus voltage may be greater than or equal to 600V, and the output line voltage of the generator may be greater than or equal to 690V.

[0014] According to an embodiment of the present disclosure, the DC bus voltage may be 1800V, the output line voltage of the generator may be 1380V, and the output line voltage of the generator may be 1250V.

[0015] According to an embodiment of the present disclosure, the converter may include a rectifier, an input end of the rectifier may be connected to the secondary side of the transformer, and an output end of the rectifier may be connected to the DC bus.

[0016] According to an embodiment of the present disclosure, the converter may further include a DC-DC converter, one side of the DC-DC converter may be connected to the output end of the rectifier, and the other side of the DC-DC converter may be connected to the DC load of the wind turbine generator set.

[0017] According to an embodiment of the present disclosure, the wind turbine generator set may further include a machine-side filter connected between the generator and the transformer.

[0018] According to an embodiment of the present disclosure, the wind turbine generator set may further include a machine-side contactor connected between the generator and the machine-side filter.

[0019] According to a second aspect of the present disclosure, a wind turbine generator set is provided, which may include: a generator; a voltage conversion module, an input end of the voltage conversion module is connected to the generator; and a converter, an input end of the converter is connected to an output end of the voltage conversion module.

[0020] According to an embodiment of the present disclosure, the voltage conversion module is an AC-AC converter.

[0021] According to an embodiment of the present disclosure, the DC bus voltage of the converter may be greater than the machine-side input voltage of the converter, the machine-side input voltage may be less than the output line voltage of the generator, and the difference between the machine-side input voltage and the output line voltage of the generator is greater than or equal to 40V.

[0022] According to the embodiment of the present disclosure, the wind turbine generator set adopts a new machine-side transformer topology solution, which can improve the stability of the machine-side control system and enhance the operational safety of the wind turbine generator set. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Detailed description is a system block diagram of a wind turbine generator system according to a first embodiment of the present disclosure.

[0024] Figure 2 is a system block diagram showing a wind turbine generator set according to a second embodiment of the present disclosure.

[0025] Figure 3 is a system block diagram showing a wind turbine generator set according to a third embodiment of the present disclosure.

[0026] Hereinafter, the present disclosure will be described in detail with reference to the accompanying drawings, and the same or similar elements will be indicated by the same or similar reference numerals throughout the accompanying drawings. DETAILED DESCRIPTION

[0027] The following detailed description is provided to help gain a comprehensive understanding of the methods, devices and / or systems described herein. However, the order of operations described herein is only an example and is not limited to those orders set forth herein, but may be equivalently replaced or changed except for operations that must occur or be performed in a specific order. In addition, for greater clarity and simplicity, the description of content known in the art will be omitted or simplified.

[0028] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art to which the present disclosure belongs after understanding the present disclosure. Unless explicitly defined as such herein, terms (such as those defined in general dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure, and should not be interpreted in an idealized or overly formal manner.

[0029] Unless otherwise specified, the same reference numerals generally refer to the same elements (e.g., components, steps, and methods). Reference numerals described in previous embodiments may be omitted if they appear again in later embodiments. In addition, the technical features described in different or the same embodiments may be combined in any manner, as long as the combined embodiments or technical solutions are complete and can solve the technical problems of the present application or achieve the technical effects described or not described in the present disclosure but can be determined based on the above complete technical solutions.

[0030] The DC bus voltage of the wind turbine is the input voltage of the converter. Taking the DC bus voltage as 1800V as an example, the converter input voltage is around 1270V (1800 / ), for example, the input voltage of the converter is 1250V. If the rated output voltage of the wind turbine generator set is reduced to about 1270V, for example, 1250V, according to the current control scheme for the generator (for example, adjusting the excitation current of the generator, etc.), it is difficult to reduce the output line voltage of the wind turbine generator set from 1380V to about 1270V (for example, it is difficult to reduce the output line voltage of the wind turbine generator set from 1380V to 1250V, or even to 1300V), and the applicant of the present disclosure has found that excessively reducing the output line voltage of the generator will cause the generator to enter a weak magnetic state.

[0031] Not only when the DC bus voltage is 1800V, but also when the DC bus voltage is 600V, 1200V, etc., when the output line voltage of the wind turbine needs to be reduced to a converter input voltage that meets the requirements, the generator may enter a state of deep magnetic weakening. When the generator is in a state of deep magnetic weakening, it will not only affect the performance of the generator, but also affect the stability and reliability of the entire wind power generation system.

[0032] The present disclosure provides a voltage conversion module such as a transformer and an AC-AC converter between the wind turbine generator and the converter, thereby eliminating the need to over-modulate the generator and preventing the generator from entering a deep magnetic weakening state. In addition, the requirements of various voltage levels of DC loads can be met, and the wind turbine generator set disclosed in the present disclosure can improve operational safety.

[0033] The voltage conversion module of the present disclosure may be a step-down conversion module. Depending on the magnitude of the output line voltage of the generator, in order to meet the requirements of different DC loads, the voltage conversion module of the present disclosure may also be a step-up conversion module. However, when it is necessary to step up the output voltage of the wind turbine generator to a converter input voltage that meets the requirements, the generator generally does not enter a deep magnetic weakening state.

[0034] As an example, the output line voltage or rated voltage of the generator of the wind turbine generator set of the present disclosure may be 690V, 1000V, 1380V, etc. The following is a detailed description in conjunction with the embodiments of the present disclosure.

[0035] Figure 1 is a system block diagram showing a wind turbine generator set according to a first embodiment of the present disclosure, Figure 2 is a system block diagram showing a wind turbine generator set according to a second embodiment of the present disclosure, Figure 3 is a system block diagram showing a wind turbine generator set according to a third embodiment of the present disclosure.

[0036] Reference Figure 1 According to the first embodiment of the present disclosure, the wind turbine generator set may include a generator, a voltage conversion module and a converter. The voltage conversion module here is used to change the input voltage of the converter, and the voltage conversion module can be used to reduce the output line voltage of the generator 3 to the required voltage, so the voltage conversion module can be a step-down conversion module. The voltage conversion module can be implemented by a transformer or an AC-AC converter.

[0037] The input end of the voltage conversion module can be connected to the generator 3, and the input end of the converter can be connected to the output end of the voltage conversion module. Figure 1The converter of the wind turbine generator set disclosed in the present invention may include a rectifier, a DC-DC converter and a support capacitor (not shown). This is only an example. The converter of the wind turbine generator set disclosed in the present invention may also include a rectifier, an inverter and a support capacitor. In addition, the support capacitor is arranged on the DC bus between the rectifier and the inverter or the rectifier and the DC-DC converter to keep the DC bus voltage stable. In addition, the support capacitor can also filter out ripples, provide instantaneous energy buffering and support the stable operation of the system.

[0038] The voltage conversion ratio (input voltage / output voltage) of the voltage conversion module may be greater than or equal to 1.02, greater than or equal to 1.06, greater than or equal to 1.2, greater than or equal to 1.5, greater than or equal to 2, etc. The upper limit value of the voltage conversion ratio (input voltage / output voltage) of the voltage conversion module is not specifically limited.

[0039] The input end of the rectifier is connected to the voltage conversion module, and the output end of the rectifier is connected to the support capacitor and to the input end of the inverter or the DC-DC converter.

[0040] Reference Figure 1 , the wind turbine converts the captured wind energy into mechanical energy, and then converts the mechanical energy into electrical energy (AC). The voltage conversion module converts the output voltage of the generator 3 into the input voltage (AC) required by the converter. As the internal switching device (e.g., IGBT) of the rectifier turns on and off, the input AC is converted into DC. The rectified DC is charged into the support capacitor, which smoothes the DC output of the rectifier and provides stable and smooth DC, which can then be output to the outside (e.g., to an external DC-DC converter). In addition, the DC smoothed by the support capacitor can be transmitted to an inverter or a DC-DC converter. The inverter or DC-DC converter converts the DC into the required DC and outputs it.

[0041] As an example, when the converter includes an inverter, direct current can be converted into alternating current and then output, and the output alternating current can be used to power a load (eg, an AC load) on the wind turbine side.

[0042] Reference Figures 1 to 3, the wind turbine generator set of the present disclosure may further include an impeller 1. In addition, the wind turbine generator set of the present disclosure may further include a gearbox 2. The main shaft of the impeller 1 is connected to the input shaft of the gearbox 2 through a coupling, and the impeller 1 captures wind energy and converts it into mechanical energy, which is then transmitted to the gearbox 2 through the main shaft. The output shaft of the gearbox 2 is connected to the rotor of the generator through a coupling, whereby the gearbox 2 can convert the low-speed rotation of the impeller 1 into high-speed rotation, which is transmitted to the rotor of the generator through the output shaft. However, this is merely an example, and the wind turbine generator set of the present disclosure may also have other configurations. Exceptionally, in addition to a full-power wind turbine generator set, the wind turbine generator set of the present disclosure may also be a direct-drive wind turbine generator set or a semi-direct-drive wind turbine generator set.

[0043] The wind turbine generator disclosed in the present invention can be a DC wind turbine generator, and the wind turbine generator set disclosed in the present invention can supply power to the outside through a DC bus. The outside here refers to the outside of the converter. The DC fan can directly transmit power to the outside through the DC bus, without the need to be converted by an inverter before supplying power to the load outside the fan. Since the DC wind turbine generator can directly output DC power, the system structure can be simplified, reducing the number and complexity of equipment. This not only reduces the initial investment cost of the system, but also reduces the workload of maintenance and repair, and improves the reliability and stability of the system.

[0044] As an example, the DC bus of the converter may be connected to an external load via a DC-DC converter, for example, a load requiring 1800V DC power or a load having a voltage that can be obtained by DC-DC conversion of 1800V DC power.

[0045] The DC bus voltage of the converter is greater than the machine-side input voltage of the converter, and the machine-side input voltage is less than the output line voltage of the generator. In addition, the difference between the machine-side input voltage and the output line voltage of the generator may be greater than or equal to 40V. As an example, the difference between the machine-side input voltage and the output line voltage of the generator may be greater than or equal to 80V, and as an example, the difference between the machine-side input voltage and the output line voltage of the generator may be 110V (i.e., 1380V-1270V=110V).

[0046] Reference Figure 2 According to the second embodiment of the present disclosure, a wind turbine generator set may include a generator, a transformer and a converter.

[0047] The input end of the transformer can be connected to the generator, and the input end of the converter can be connected to the secondary side of the transformer. In addition, the converter of the wind turbine generator set disclosed in the present invention may include a rectifier, a DC-DC converter, and a support capacitor (not shown). However, this is only an example, and the converter of the wind turbine generator set disclosed in the present invention may also include a rectifier, an inverter, and a support capacitor.

[0048] As an example, the support capacitor is arranged on the DC bus between the rectifier and the inverter or the rectifier and the DC-DC converter to keep the DC bus voltage stable. In addition, the support capacitor can also filter ripples, provide instantaneous energy buffering and support the stable operation of the system. The output end of the inverter can be connected to the load. As an example, although not shown, the output end of the inverter can be connected to the AC load via a transformer.

[0049] Reference Figure 2 The output of the DC-DC converter of the converter can be connected to a DC load. As an example, the output of the DC-DC converter can also be connected to other loads via a DC transformer. These loads may require different voltage amplitudes.

[0050] Reference Figure 2 , the input end of the rectifier is connected to the transformer, the output end of the rectifier is connected to the support capacitor and connected to the input end of the inverter or the DC-DC converter.

[0051] The voltage of the DC bus of the converter (i.e., the DC bus voltage) is greater than the machine-side input voltage of the converter. The machine-side input voltage of the converter may be the input voltage of the rectifier, and the machine-side input voltage of the converter may be less than the output line voltage of the generator. At this time, when the voltage required for the generator output cannot be controlled or the voltage input to the input terminal of the converter needs to be reduced to avoid the generator entering a deep magnetic weakening state, the output line voltage of the generator may be stepped down by a transformer.

[0052] As an example, the difference between the machine-side input voltage of the converter and the output line voltage of the generator may be greater than or equal to 40 V, greater than or equal to 50 V, or greater than or equal to 80 V. Taking the output line voltage of the generator as 1380 V as an example, it is difficult to reduce the output line voltage of the generator to 1300 V or less by controlling the excitation current of the generator. The technical solution disclosed in the present invention is particularly suitable for this situation, thereby preventing the wind turbine generator from entering a deep magnetic weakening state.

[0053] Specifically, the turns ratio n of the generator can be calculated by formula (1): n=N2 / N1=V2 / V1 (1) Where: N1 is the number of turns of the primary winding of the transformer, N2 is the number of turns of the secondary winding of the transformer, V1 is the voltage of the primary winding (i.e., the input voltage), and V2 is the voltage of the secondary winding (i.e., the output voltage).

[0054] As an example, the voltage V1 of the primary winding (the output line voltage of the generator) is 1380V. If the DC bus voltage is required to be 1800V, the voltage on the input side of the converter is required to be about 1270V, for example, 1250V, that is, the voltage V2 of the secondary winding is required to be 1250V, and the turns ratio can be about 1.1. For example, if the number of turns N1 of the primary winding is 1100 turns, then the number of turns N2 of the secondary winding can be about 997. The transformer can reduce the input voltage of 1380V to an output voltage of about 1270V, thereby ensuring that the input voltage of the converter is within a reasonable range and preventing the wind turbine from entering a deep magnetic weakening state.

[0055] When the DC bus voltage is 1800V, the generator output line voltage is 1380V, and the generator output line voltage is 1250V, it does not mean that the DC bus voltage is strictly required to be 1800V, the generator output line voltage is 1380V, and the generator output line voltage is 1250V, but these voltages can fluctuate within a certain range. For details, please refer to the requirements of the relevant standards for the corresponding voltage fluctuations. For example, taking the DC bus voltage as an example, the actual DC bus voltage can refer to the fluctuation range of the DC bus voltage clearly required in the wind power generation system standard issued by the International Electrotechnical Commission (IEC).

[0056] The turns ratio of the transformer may be greater than or equal to 1.02, greater than or equal to 1.06, greater than or equal to 1.2, greater than or equal to 1.5, greater than or equal to 2, etc. The upper limit value of the turns ratio (input voltage / output voltage) of the transformer is not particularly limited.

[0057] In addition to reducing the input voltage of the converter, the transformer of the present invention can also isolate the generator and the converter, prevent electrical interference between the generator and the converter, improve the safety and reliability of the system, and prevent faults such as short circuit and overload from being transmitted from one side to the other, protecting the generator and the converter from damage.

[0058] As an example, an overload protection function can be designed for the transformer. When the system is overloaded or short-circuited, the transformer can automatically disconnect to protect the system from damage. In addition, the transformer can isolate the fault area to prevent the fault from spreading, thereby improving the safety and reliability of the system.

[0059] The turns ratio of the transformer may be a fixed turns ratio, and the turns ratio may be predetermined according to requirements of the DC load and the DC bus voltage.

[0060] As an example, the transformer in the wind turbine generator set of the embodiment of the present disclosure may be an autotransformer. An autotransformer can achieve different voltage ratios through different taps. The primary winding and the secondary winding share a portion of the winding, so it is more compact and lighter than an ordinary transformer. By changing the position of the tap, the autotransformer can achieve different voltage ratios and provide a voltage regulation function.

[0061] The turns ratio of the transformer can be changed according to the requirements of the DC load and the DC bus voltage, so that it can adapt to more loads that require different DC voltages. In addition, compared with ordinary transformers, autotransformers have obvious advantages in high efficiency and energy saving, small size, light weight, voltage regulation and dynamic response.

[0062] Reference Figure 2 The input end of the rectifier in the converter is connected to the secondary side of the transformer, and the output end of the rectifier is connected to the DC bus. The converter may also include a DC-DC converter, one side of the DC-DC converter is connected to the output end of the rectifier, and the other side of the DC-DC converter is connected to the DC load of the wind turbine generator set.

[0063] and Figure 2 The construction shown is different. Figure 3 The voltage conversion module is implemented as an AC / AC converter. The input end of the AC / AC converter can be connected to the generator, and the input end of the converter can be connected to the output end or output side of the AC / AC converter.

[0064] In addition, refer to Figure 3 The converter of the wind turbine generator set of the present disclosure may include a rectifier (AC / DC converter), a DC-DC converter and a support capacitor (not shown). However, this is only an example, and the converter of the wind turbine generator set of the present disclosure may also include a rectifier, an inverter and a support capacitor.

[0065] As an example, the support capacitor is set on the DC bus between the rectifier and the inverter or the rectifier and the DC-DC converter to keep the DC bus voltage stable. In addition, the support capacitor can also filter ripples, provide transient energy buffering and support stable operation of the system. The output end of the inverter can be connected to the load. As an example, the output end of the inverter can be connected to the AC load via a DC / AC converter. Figure 3 The output of the DC-DC converter can be connected to a DC load. As an example, the output of the DC-DC converter can also be connected to other loads via a DC AC / AC converter. These loads can have different voltage amplitudes.

[0066] Reference Figure 3, the input end of the rectifier is connected to the AC / AC converter, and the output end of the rectifier is connected to the support capacitor and to the input end of the inverter or DC-DC converter.

[0067] The voltage at the output end of the AC / AC converter is lower than the voltage of the DC bus of the converter (i.e., the DC bus voltage), the machine-side input voltage of the converter may refer to the input voltage of the rectifier, and the voltage at the output end of the AC / AC converter may be lower than the output line voltage of the generator, i.e., the voltage at the output end of the AC / AC converter is lower than the voltage at the input end of the AC / AC converter. At this time, when it is difficult to control the voltage required for the generator output or it is necessary to reduce the voltage input to the input end of the converter in order to avoid the generator entering a deep magnetic weakening state, the output line voltage of the generator is stepped down by the AC / AC converter.

[0068] As an example, the difference between the machine-side input voltage and the output line voltage of the generator may be greater than or equal to 40 V, greater than or equal to 50 V, or greater than or equal to 80 V. Taking the output line voltage of the generator as 1380 V as an example, it is difficult to reduce the output line voltage of the generator to 1300 V or less by controlling the excitation current of the generator. The AC / AC converter of the present disclosure can reduce the voltage input to the converter, and in addition, it can prevent the wind turbine from entering a deep magnetic weakening state.

[0069] The voltage conversion ratio of the AC / AC converter may be greater than or equal to 1.02, greater than or equal to 1.06, greater than or equal to 1.2, greater than or equal to 1.5, greater than or equal to 2, etc. The upper limit value of the voltage conversion ratio (input voltage / output voltage) of the AC / AC converter is not particularly limited.

[0070] Compared with a transformer, an AC / AC converter can have higher control accuracy and can more conveniently adjust the machine-side input voltage of the converter of a wind turbine generator set to a required voltage level.

[0071] Although not shown, the wind turbine generator system of the present disclosure may further include at least one of a machine-side filter and a machine-side contactor.

[0072] As an example, the machine side filter may be connected between the generator and the voltage conversion module, transformer or AC-AC converter. The machine side contactor of the present disclosure may be connected between the generator and the machine side filter. As an example, the contactor and the machine side filter may be connected in series between the generator and the conversion module, transformer or AC-AC converter.

[0073] The wind turbine generator set according to the embodiment of the present disclosure can prevent the generator from entering a deep magnetic weakening state.

[0074] The wind turbine generator set according to the embodiment of the present disclosure can adjust different bus voltage levels to meet different DC load requirements.

[0075] The wind turbine generator set according to the embodiment of the present disclosure can stabilize the input voltage on the machine side of the converter.

[0076] According to the embodiment of the present disclosure, the wind turbine generator set adopts a new machine-side transformer topology solution, which can improve the stability of the machine-side control system and enhance the operational safety of the wind turbine generator set.

[0077] The specific implementation methods of the present disclosure are described in detail above. Although some embodiments have been shown and described, those skilled in the art should understand that these embodiments can be combined, modified and improved without departing from the principles and spirit of the present disclosure whose scope is defined by the claims and their equivalents. These combinations, modifications and improvements should also be within the scope of protection of the present disclosure.

Claims

1. A wind turbine generator set, characterized in that: The wind turbine generator set comprises: dynamo; a transformer having a primary side connected to the generator; a converter, the input of which is connected to the secondary side of the transformer, The DC bus voltage of the converter is greater than the machine-side input voltage of the converter, and the machine-side input voltage is less than the output line voltage of the generator.

2. The wind turbine generator set according to claim 1, characterized in that: The difference between the generator-side input voltage and the generator output line voltage is greater than or equal to 40V.

3. The wind turbine generator set according to claim 1, characterized in that: The turns ratio of the transformer is greater than or equal to 1.

02.

4. The wind turbine generator set according to claim 3, characterized in that: The transformer is an autotransformer.

5. The wind turbine generator set according to claim 1, characterized in that: The DC bus voltage is greater than or equal to 600V, and the output line voltage of the generator is greater than or equal to 690V.

6. The wind turbine generator set according to claim 4, characterized in that: The DC bus voltage is 1800V, the output line voltage of the generator is 1380V, and the output line voltage of the generator is 1250V.

7. The wind turbine generator set according to claim 1, characterized in that: The converter includes a rectifier, an input end of the rectifier is connected to the secondary side of the transformer, and an output end of the rectifier is connected to a DC bus.

8. The wind turbine generator set according to claim 7, characterized in that: The converter further comprises a DC-DC converter, one side of which is connected to the output end of the rectifier, and the other side of which is connected to the DC load of the wind generator set.

9. The wind turbine generator set according to any one of claims 1 to 8, characterized in that: The wind turbine generator set further includes a machine-side filter, and the machine-side filter is connected between the generator and the transformer.

10. The wind turbine generator set according to claim 9, characterized in that: The wind turbine generator set further includes a machine-side contactor, which is connected between the generator and the machine-side filter.

11. A wind turbine generator set, characterized in that: The wind turbine generator set comprises: dynamo; a voltage conversion module, wherein an input end of the voltage conversion module is connected to the generator; A converter, wherein the input end of the converter is connected to the output end of the voltage conversion module.

12. The wind turbine generator set according to claim 11, characterized in that: The voltage conversion module is an AC-AC converter or a transformer.

13. The wind turbine generator set according to claim 11 or 12, characterized in that: The DC bus voltage of the converter is greater than the machine-side input voltage of the converter, and the machine-side input voltage is less than the output line voltage of the generator, and the difference between the machine-side input voltage and the output line voltage of the generator is greater than or equal to 40V.

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