A direct current fan and wind turbine generator set

Abstract

The application discloses a direct-current fan and a wind turbine generator unit, which comprises blades, a gear box, a generator and a rectifier. A bridge arm midpoint of the rectifier is connected with a rotor winding. An upper bridge arm comprises a first multi-level converter, a first diode and a second diode. A lower bridge arm comprises a second multi-level converter, a third diode and a fourth diode. The first end and the second end of the first multi-level converter are respectively connected with the anode of the first diode and the bridge arm midpoint, and the cathode of the first diode is connected with the positive output end of the rectifier. The cathode of the second diode is connected with the anode of the first diode, and the anode of the second diode is connected with a common neutral point. The first end and the second end of the second multi-level converter are respectively connected with the bridge arm midpoint and the anode of the third diode, and the cathode of the third diode is connected with the common neutral point. The cathode of the fourth diode is connected with the anode of the third diode, and the anode of the fourth diode is connected with the negative output end of the rectifier. The fan has simple structure, low cost and small loss.

Description

Technical Field

[0001] This application relates to the field of wind power generation technology, specifically to a DC wind turbine and a wind turbine generator set. Background Technology

[0002] Wind turbine generators mostly use AC turbines connected to the AC power grid. However, AC turbines have drawbacks such as high manufacturing costs and significant operating losses, resulting in low overall operating efficiency of wind power systems. Furthermore, when multiple AC turbines are connected to the grid via AC lines, the resulting AC aggregation network suffers from high reactive power losses and poor voltage stability at the aggregation bus, and is prone to various power quality issues, including wide-bandwidth resonance.

[0003] Therefore, to solve the above technical problems, DC wind turbines can be directly connected to the DC power grid. However, existing DC wind turbines typically employ multi-stage power conversion structures, resulting in a large number of conversion stages, complex structures, high hardware costs, and energy loss issues. Summary of the Invention

[0004] In view of this, this application provides a DC wind turbine and wind power generator set, which has a simple structure, low cost, and low loss.

[0005] This application provides a DC fan, including: blades, gearbox, generator and rectifier; The blades are connected to a gearbox, and the gearbox is connected to the rotor in the generator; The rotor winding of the generator is connected to the input terminal of the rectifier; The rectifier includes at least three bridge arms, with the midpoint of each bridge arm connected to the corresponding phase of the rotor winding. Each upper bridge arm includes a first multilevel converter, a first diode, and a second diode; each lower bridge arm includes a second multilevel converter, a third diode, and a fourth diode. The first terminal of the first multilevel converter is connected to the anode of the first diode, and the cathode of the first diode is connected to the positive output terminal of the rectifier; the second terminal of the first multilevel converter is connected to the midpoint of the bridge arm; the cathode of the second diode is connected to the anode of the first diode, and the anode of the second diode is connected to the common neutral point; The first end of the second multilevel converter is connected to the midpoint of the bridge arm; the second end of the second multilevel converter is connected to the anode of the third diode, and the cathode of the third diode is connected to the common neutral point; the cathode of the fourth diode is connected to the anode of the third diode, and the anode of the fourth diode is connected to the negative output terminal of the rectifier.

[0006] In one possible implementation, both the first multilevel converter and the second multilevel converter include: a bridge arm inductor and multiple sub-modules connected in series; The submodule includes a full-bridge circuit or a half-bridge circuit.

[0007] One possible implementation also includes: a resonant switched-capacitor DC-DC converter; The input terminal of the resonant switched capacitor DC-DC converter is connected to the output terminal of the rectifier, and is used to boost the output voltage of the rectifier before outputting it.

[0008] One possible implementation is that the resonant switched capacitor DC-DC converter includes: a first switching transistor, a second switching transistor, a first resonant branch, and a second resonant branch; The first end of the first switching transistor is connected to the positive output terminal of the rectifier, the second end of the first switching transistor is connected to the first end of the second switching transistor, and the second end of the second switching transistor is connected to the negative output terminal of the rectifier. The first end of the first resonant branch is connected to the first end of the first switching transistor, and the second end of the first resonant branch serves as the positive output terminal of the resonant switched capacitor DC-DC converter. The first end of the second resonant branch is connected to the second end of the second switching transistor, and the second end of the second resonant branch serves as the negative output terminal of the resonant switched capacitor DC-DC converter. Both the first resonant branch and the second resonant branch include multiple resonant cavities connected in series.

[0009] In one possible implementation, the resonant cavity includes: a fifth diode, a sixth diode, a first LC resonant circuit, and a second LC resonant circuit; both the first LC resonant circuit and the second LC resonant circuit include a resonant capacitor and a resonant inductor connected in series. The anode of the fifth diode is connected to the cathode of the sixth diode; the first terminal and the second terminal of the first LC resonant circuit are respectively connected to the cathode of the fifth diode and the anode of the sixth diode; the first terminal of the second LC resonant circuit is connected to the cathode of the sixth diode, and the second terminal of the second LC resonant circuit is connected to the anode of the fifth diode in the adjacent resonant cavity; Both the resonant capacitor in the first LC resonant circuit and the resonant capacitor in the second LC resonant circuit are periodically charged and discharged during the switching cycle of the resonant switched capacitor DC-DC converter. The energy of the resonant capacitor in the first LC resonant circuit and the resonant capacitor in the second LC resonant circuit during charging and discharging participates in the resonant energy transfer through the resonant inductor in the first LC resonant circuit and the resonant inductor in the second LC resonant circuit, respectively.

[0010] One possible implementation is that the resonant cavity includes: a fifth diode, a sixth diode, and a third LC resonant circuit; the third LC resonant circuit includes a first capacitor, a resonant capacitor, and a resonant inductor; The anode of the fifth diode is connected to the cathode of the sixth diode, the first terminal of the first capacitor is connected to the cathode of the fifth diode, and the second terminal of the first capacitor is connected to the anode of the sixth diode. The first end of the series connection between the resonant capacitor and the resonant inductor is connected to the cathode of the sixth diode, and the second end of the series connection between the resonant capacitor and the resonant inductor is connected to the anode of the fifth diode in the adjacent resonant cavity. The capacitance value of the resonant capacitor and the capacitance value of the first capacitor are on the same order of magnitude, so that the voltage across the resonant capacitor and the voltage across the first capacitor change periodically during the resonance process.

[0011] One possible implementation is that the common neutral point is directly grounded.

[0012] One possible implementation is that the common neutral point is grounded via impedance.

[0013] One possible implementation is that the common neutral point is left floating.

[0014] This application also provides a wind turbine generator set, including the DC wind turbine described above.

[0015] The embodiments provided in this application have the following beneficial effects: The DC fan provided in this application embodiment includes at least three bridge arms of rectifiers. The midpoint of each bridge arm connects to the corresponding phase of the rotor winding. Each upper bridge arm includes a modular first multilevel converter, a first diode, and a second diode; each lower bridge arm includes a second multilevel converter, a third diode, and a fourth diode. Since the upper and lower bridge arms of the same bridge arm alternate conduction, the first diode of each upper bridge arm and the third diode of each lower bridge arm serve as the current path for the positive half-wave and are cut off during the negative half-wave; the fourth diode of each lower bridge arm and the second diode of each upper bridge arm serve as the current path for the negative half-wave and are cut off during the positive half-wave. Therefore, by utilizing the voltage clamping effect of these four diodes, the first and second multilevel converters do not need to bear the entire DC voltage on the DC side. Thus, the withstand voltage of the first and second multilevel converters does not need to be very high; they only need to withstand the voltage during the positive or negative half-wave. Therefore, the hardware size of the first and second multilevel converters is smaller, reducing engineering costs and floor space. The DC fan provided in this application embodiment has a simple structure, low cost, and low loss. Attached Figure Description

[0016] Figure 1This is an architectural diagram of a DC fan; Figure 2 A schematic diagram of a first type of DC fan provided in an embodiment of this application; Figure 3 A schematic diagram of a modular multilevel converter provided in an embodiment of this application; Figure 4 A schematic diagram of a second type of DC fan provided in an embodiment of this application; Figure 5 A schematic diagram of a third type of DC fan provided in an embodiment of this application; Figure 6 This is a schematic diagram of a first type of DC-DC converter provided in an embodiment of this application; Figure 7 This is a schematic diagram illustrating the working principle of a first type of DC-DC converter provided in an embodiment of this application; Figure 8 This is a schematic diagram illustrating the working principle of a second type of DC-DC converter provided in an embodiment of this application; Figure 9 This is a schematic diagram of a second type of DC-DC converter provided in an embodiment of this application. Detailed Implementation

[0017] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0018] Wind turbine generators mostly use AC turbines connected to the AC power grid. However, AC turbines have drawbacks such as high manufacturing costs and significant operating losses, resulting in low overall operating efficiency of wind power systems. Furthermore, when multiple AC turbines are connected to the grid via AC lines, the resulting AC aggregation network suffers from high reactive power losses and poor voltage stability at the aggregation bus, and is prone to various power quality issues, including wide-bandwidth resonance.

[0019] Therefore, to solve the above technical problems, DC wind turbines can be directly connected to the DC power grid. However, existing DC wind turbines typically employ multi-stage power conversion structures, resulting in high hardware costs and energy loss issues.

[0020] See Figure 1 The diagram shows the architecture of a DC fan.

[0021] Existing DC wind turbines consist of a two-stage architecture: an AC / DC converter and a DC / DC converter. Furthermore, the DC / DC converter primarily uses an isolated dual active bridge topology. This results in a large number of conversion stages in the overall DC wind turbine, leading to higher hardware costs. Additionally, the multiple energy conversion stages result in significant overall energy losses.

[0022] To address the above technical issues, this application provides a DC fan with a simple structure, low hardware cost, and low total loss.

[0023] See Figure 2 The figure is a schematic diagram of the first type of DC fan provided in the embodiments of this application.

[0024] The DC fan provided in this application embodiment includes: blades 100, gearbox 200, generator 300 and rectifier 400; blades 100 are connected to gearbox 200, gearbox 200 is connected to the rotor in generator 300; the rotor winding of generator 300 is connected to the input terminal of rectifier 400.

[0025] The rectifier 400 includes at least three bridge arms, with the midpoint of each bridge arm connected to the corresponding phase of the rotor winding. Each upper bridge arm includes a first multilevel converter, a first diode, and a second diode; each lower bridge arm includes a second multilevel converter, a third diode, and a fourth diode.

[0026] The first terminal of the first multilevel converter is connected to the anode of the first diode, and the cathode of the first diode is connected to the positive output terminal of the rectifier; the second terminal of the first multilevel converter is connected to the midpoint of the bridge arm; the cathode of the second diode is connected to the anode of the first diode, and the anode of the second diode is connected to the common neutral point N.

[0027] The first terminal of the second multilevel converter is connected to the midpoint of the bridge arm; the second terminal of the second multilevel converter is connected to the anode of the third diode, and the cathode of the third diode is connected to the common neutral point N; the cathode of the fourth diode is connected to the anode of the third diode, and the anode of the fourth diode is connected to the negative output terminal of the rectifier.

[0028] This application takes a rectifier 400 with three bridge arms as an example and provides a detailed description in conjunction with the accompanying drawings.

[0029] The midpoint of the A-phase bridge arm is connected to the A-phase of the rotor winding. The upper A-phase bridge arm includes the first multilevel converter A_p, the first diode DA1, and the second diode DA2 of the A-phase. The lower A-phase bridge arm includes the second multilevel converter A_n, the third diode DA3, and the fourth diode DA4 of the A-phase.

[0030] The first terminal of the first multilevel converter A_p in phase A is connected to the anode of the first diode DA1 in phase A, and the cathode of the first diode DA1 in phase A is connected to the positive output terminal of rectifier 400; the second terminal of the first multilevel converter A_p in phase A is connected to the midpoint of the bridge arm; the cathode of the second diode DA2 in phase A is connected to the anode of the first diode DA1 in phase A, and the anode of the second diode DA2 in phase A is connected to the common neutral point N.

[0031] The first terminal of the second multilevel converter A_n in phase A is connected to the midpoint of the bridge arm; the second terminal of the second multilevel converter A_n in phase A is connected to the anode of the third diode DA3 in phase A, and the cathode of the third diode DA3 in phase A is connected to the common neutral point N; the cathode of the fourth diode DA4 in phase A is connected to the anode of the third diode DA3 in phase A, and the anode of the fourth diode DA4 in phase A is connected to the negative output terminal of rectifier 400.

[0032] The midpoint of the B-phase bridge arm is connected to the B-phase of the rotor winding. The upper B-phase bridge arm includes the first multilevel converter B_p, the first diode DB1, and the second diode DB2 of the B-phase. The lower B-phase bridge arm includes the second multilevel converter B_n, the third diode DB3, and the fourth diode DB4 of the B-phase.

[0033] The first terminal of the B-phase first multilevel converter B_p is connected to the anode of the B-phase first diode DB1, and the cathode of the B-phase first diode DB1 is connected to the positive output terminal of the rectifier 400; the second terminal of the B-phase first multilevel converter B_p is connected to the midpoint of the bridge arm; the cathode of the B-phase second diode DB2 is connected to the anode of the B-phase first diode DB1, and the anode of the B-phase second diode DB2 is connected to the common neutral point N.

[0034] The first terminal of the second multilevel converter B_n in phase B is connected to the midpoint of the bridge arm; the second terminal of the second multilevel converter B_n in phase B is connected to the anode of the third diode DB3 in phase B, and the cathode of the third diode DB3 in phase B is connected to the common neutral point N; the cathode of the fourth diode DB4 in phase B is connected to the anode of the third diode DB3 in phase B, and the anode of the fourth diode DB4 in phase B is connected to the negative output terminal of rectifier 400.

[0035] The C-phase bridge arm is connected to the C-phase of the rotor winding at the midpoint of the bridge arm. The upper C-phase bridge arm includes the C-phase first multilevel converter C_p, the C-phase first diode DC1, and the C-phase second diode DC2. The lower C-phase bridge arm includes the C-phase second multilevel converter C_n, the C-phase third diode DC3, and the C-phase fourth diode DC4.

[0036] The first terminal of the C-phase first multilevel converter C_p is connected to the anode of the C-phase first diode DC1, and the cathode of the C-phase first diode DC1 is connected to the positive output terminal of the rectifier 400; the second terminal of the C-phase first multilevel converter C_p is connected to the midpoint of the bridge arm; the cathode of the C-phase second diode DC2 is connected to the anode of the C-phase first diode DC1, and the anode of the C-phase second diode DC2 is connected to the common neutral point N.

[0037] The first terminal of the C-phase second multilevel converter C_n is connected to the midpoint of the bridge arm; the second terminal of the C-phase second multilevel converter C_n is connected to the anode of the C-phase third diode DC3, and the cathode of the C-phase third diode DC3 is connected to the common neutral point N; the cathode of the C-phase fourth diode DC4 is connected to the anode of the C-phase third diode DC3, and the anode of the C-phase fourth diode DC4 is connected to the negative output terminal of the rectifier 400.

[0038] This application does not specifically limit the type of generator 300. Generator 300 can be one of permanent magnet synchronous generator, permanent magnet asynchronous generator, excitation synchronous generator and excitation asynchronous generator.

[0039] The operation of the rectifier 400 of the DC fan will be introduced, taking phase A as an example.

[0040] The upper and lower arms of phase A are not constantly connected; during the working cycle, the upper and lower arms of phase A are alternately conducting. The first diode DA1 of phase A in the upper arm and the third diode DA3 of phase A in the lower arm serve as the current path during the positive half-wave period of phase A voltage and are cut off during the negative half-wave period. The fourth diode DA4 of phase A in the lower arm and the second diode DA2 of phase A in the upper arm serve as the current path during the negative half-wave period of phase A voltage and are cut off during the positive half-wave period.

[0041] Because the first diode DA1, the second diode DA2, the third diode DA3, and the fourth diode DA4 of phase A have a cutoff period during the alternating conduction of the upper and lower arms of phase A, the first multilevel converter A_p and the second multilevel converter A_n of phase A do not need to bear the large voltage difference between the DC positive bus voltage and the DC negative bus voltage when the upper and lower arms of phase A are connected. They only need to bear the voltage during the positive or negative half-wave. Therefore, the withstand voltage of the first multilevel converter A_p and the second multilevel converter A_n of phase A does not need to be very high, and the hardware size can be greatly reduced, thus reducing the engineering cost and floor space.

[0042] The working principle of the other phases is the same as that of phase A, and will not be repeated here.

[0043] The DC fan provided in this application embodiment includes at least three bridge arms of rectifiers. The midpoint of each bridge arm connects to the corresponding phase of the rotor winding. Each upper bridge arm includes a first multilevel converter, a first diode, and a second diode; each lower bridge arm includes a second multilevel converter, a third diode, and a fourth diode. Since the upper and lower bridge arms of the same bridge arm conduct alternately, the first diode of each upper bridge arm and the third diode of each lower bridge arm serve as the current path for the positive half-wave and are cut off during the negative half-wave; the fourth diode of each lower bridge arm and the second diode of each upper bridge arm serve as the current path for the negative half-wave and are cut off during the positive half-wave. The first and second multilevel converters do not need to have very high withstand voltage; they only need to withstand the voltage during the positive or negative half-wave. Therefore, the hardware size of the first and second multilevel converters is smaller, reducing engineering costs and floor space. The DC fan provided in this application embodiment has a simple structure, low cost, and low losses.

[0044] The implementation methods of the first and second multilevel converters of DC wind turbines are described below, with detailed explanations in conjunction with the accompanying drawings.

[0045] The first and second multilevel converters of the DC fan provided in this application embodiment both include bridge arm inductors and multiple sub-modules connected in series; the sub-modules include full-bridge circuits or half-bridge circuits.

[0046] See Figure 3 The figure is a schematic diagram of a modular multilevel converter provided in an embodiment of this application.

[0047] Each first multilevel converter and each second multilevel converter of the DC fan provided in this application embodiment includes a bridge arm inductor L. SM The first serial submodule SM1 up to the nth serial submodule SMn, where n is an integer greater than 1.

[0048] The first series submodule SM1 up to the nth series submodule SMn can be either a full-bridge circuit 401 or a half-bridge circuit 402. When the first series submodule SM1 up to the nth series submodule SMn is a full-bridge circuit, the full-bridge circuit 401 can be a circuit combining uncontrolled diodes and controllable devices.

[0049] The first and second multilevel converters provided in this application both include bridge arm inductors and multiple sub-modules connected in series. The sub-modules can be selected according to different operating conditions, enriching the selectivity of multilevel converters in different application scenarios.

[0050] The embodiments of this application do not limit the state of the common neutral point of the rectifier of the DC fan. The common neutral point can be directly grounded, grounded through impedance, or left floating.

[0051] See Figure 4The figure is a schematic diagram of a second type of DC fan provided in an embodiment of this application.

[0052] The common neutral point N of the DC fan provided in this application embodiment is directly grounded to GND, or grounded to GND through an impedance, or left floating. It can be understood that when the common neutral point N is directly grounded to GND, the grounding device can be a conductor; when the common neutral point N is grounded to GND through an impedance, the grounding device can be an impedance; when the common neutral point N is left floating, the grounding device can be left floating.

[0053] The embodiments of this application provide multiple options for the common neutral point grounding of the DC fan, which can be selected according to different operating conditions.

[0054] Figure 4 The rest of the middle part and Figure 2 Same, see Figure 2 The description will not be repeated here.

[0055] To achieve DC-DC boost conversion, the DC fan provided in this application embodiment also includes a resonant switched capacitor DC-DC converter, which will be described in detail below with reference to the accompanying drawings.

[0056] See Figure 5 The figure is a schematic diagram of the third type of DC fan provided in the embodiments of this application.

[0057] The DC fan provided in this application embodiment also includes a resonant switched-capacitor DC-DC converter 500; the input terminal of the resonant switched-capacitor DC-DC converter 500 is connected to the output terminal of the rectifier 400, and is used to boost the output voltage of the rectifier 400 before output. It can be selected according to the voltage output requirements of the DC fan under different operating conditions, thus enriching the application scenarios of the DC fan. Figure 5 The rest of the middle part and Figure 4 Same, see Figure 4 The description will not be repeated here.

[0058] The following section provides a detailed description of the implementation of the resonant cavity of the resonant switched capacitor DC-DC converter, which includes two LC resonant circuits, with reference to the accompanying drawings.

[0059] See Figure 6 This figure is a schematic diagram of the first type of DC-DC converter provided in the embodiments of this application.

[0060] The resonant switched capacitor DC-DC converter 500 for DC fans provided in this application embodiment includes a first switching transistor S1, a second switching transistor S2, a first resonant branch 510, and a second resonant branch 520.

[0061] The first end of the first switch S1 is connected to the positive output terminal of the rectifier 400, the second end of the first switch S1 is connected to the first end of the second switch S2, and the second end of the second switch S2 is connected to the negative output terminal of the rectifier 400.

[0062] The first end of the first resonant branch 510 is connected to the first end of the first switching transistor S1, and the second end of the first resonant branch 510 serves as the positive output terminal of the resonant switched capacitor DC-DC converter 500.

[0063] The first end of the second resonant branch 520 is connected to the second end of the second switching transistor S2, and the second end of the second resonant branch 520 serves as the negative output terminal of the resonant switched capacitor DC-DC converter 500.

[0064] Both the first resonant branch 510 and the second resonant branch 520 include multiple resonant cavities connected in series.

[0065] The resonant switched-capacitor DC-DC converter for a DC fan provided in this application includes two switching transistors and two resonant branches. This resonant switched-capacitor DC-DC converter achieves output voltage boosting with fewer switching transistors, reducing hardware costs. The first resonant branch 510 and the second resonant branch 520 have a symmetrical structure. The following description, using the first resonant branch 510 as an example, details the multiple series-connected resonant cavities of the first resonant branch 510.

[0066] like Figure 6 As shown, the resonant cavity of the resonant switched capacitor DC-DC converter 500 for DC fans provided in this application embodiment includes a fifth diode D5, a sixth diode D6, a first LC resonant circuit 511, and a second LC resonant circuit 512; both the first LC resonant circuit 511 and the second LC resonant circuit 512 include a resonant capacitor Cr and a resonant inductor Lr connected in series.

[0067] The anode of the fifth diode D5 is connected to the cathode of the sixth diode D6; the first and second terminals of the first LC resonant circuit are respectively connected to the cathode of the fifth diode D5 and the anode of the sixth diode D6; the first terminal of the second LC resonant circuit is connected to the cathode of the sixth diode D6, and the second terminal of the second LC resonant circuit is connected to the anode of the fifth diode D5 in the adjacent resonant cavity.

[0068] The resonant capacitor in the first LC resonant circuit 511 and the resonant capacitor in the second LC resonant circuit 512 are periodically charged and discharged within the switching cycle of the resonant switched capacitor DC-DC converter. The energy of the resonant capacitor in the first LC resonant circuit 511 and the resonant capacitor in the second LC resonant circuit 512 participating in the resonant energy transfer through the resonant inductor in the first LC resonant circuit 511 and the resonant inductor in the second LC resonant circuit 512, respectively.

[0069] In this embodiment, neither the resonant capacitor in the first LC resonant circuit 511 nor the resonant capacitor in the second LC resonant circuit 512 serves as a DC support capacitor to maintain a constant voltage at the resonant cavity port. The capacitance values ​​of the resonant capacitors in the first LC resonant circuit 511 and the second LC resonant circuit 512 are on the same order of magnitude, allowing the voltage across both capacitors to change periodically during resonance. The fact that the capacitance values ​​of the two resonant capacitors are on the same order of magnitude quantitatively satisfies the following relationship: the ratio of the maximum value to the minimum value of the two resonant capacitors is less than or equal to 10.

[0070] The following describes the operation of the resonant switched capacitor DC-DC converter when the second switch S2 is turned on.

[0071] See Figure 7 The figure is a schematic diagram of the working principle of the first type of DC-DC converter provided in the embodiment of this application.

[0072] The output of rectifier 400 is equivalent to the input current Iin. When the second switch S2 is turned on, the first LC resonant circuit 511 forms a resonant circuit with the second LC resonant circuit 512 through the second switch S2; the resonant capacitor Cr of the first LC resonant circuit 511 charges the resonant capacitor Cr of the second LC resonant circuit 512 through resonance; the resonant capacitor Cr of the first LC resonant circuit 511 simultaneously maintains the DC current flow on the high-voltage side of the resonant switched capacitor DC converter 500.

[0073] The following describes the operation of the resonant switched capacitor DC-DC converter when the first switching transistor S1 is turned on.

[0074] See Figure 8 The figure is a schematic diagram of the working principle of the second type of DC-DC converter provided in the embodiment of this application.

[0075] The output of rectifier 400 is equivalent to the input current Iin. When the first switch S1 is turned on, the second LC resonant circuit 512 forms a resonant circuit with the first LC resonant circuit 511 through the first switch S1. The resonant capacitor Cr of the second LC resonant circuit 512 charges the resonant capacitor Cr of the first LC resonant circuit 511 through resonance. At the same time, the resonant capacitor Cr of the first LC resonant circuit 511 maintains the DC current flow on the high-voltage side of the resonant switched capacitor DC converter 500.

[0076] The resonant switched-capacitor DC-DC converter 500 achieves zero-current switching of the first switch S1 and the second switch S2 by controlling the switching period and resonant frequency, utilizing the resonance of two LC resonant circuits, thus reducing losses. The resonant switched-capacitor DC-DC converter 500 achieves energy transfer from the low-voltage DC side to the high-voltage DC side through a cascaded structure, using fewer power electronic components and reducing hardware costs. Both LC resonant circuits include a resonant capacitor Cr and a resonant inductor Lr connected in series. The two resonant inductors Lr suppress current abrupt changes and DC components, causing the voltage across the two resonant capacitors Cr to automatically tend towards balance, which is beneficial for balancing voltage fluctuations in the resonant capacitors Cr.

[0077] The resonant cavity of the DC fan provided in this application embodiment includes a fifth diode, a sixth diode, a first LC resonant circuit, and a second LC resonant circuit. Both the first and second LC resonant circuits include a resonant capacitor and a resonant inductor connected in series. The anode of the fifth diode is connected to the cathode of the sixth diode; the first and second terminals of the first LC resonant circuit are respectively connected to the cathode of the fifth diode and the anode of the sixth diode; the first terminal of the second LC resonant circuit is connected to the cathode of the sixth diode, and the second terminal of the second LC resonant circuit is connected to the anode of the fifth diode in an adjacent resonant cavity.

[0078] The DC fan provided in this application reduces losses by controlling the switching cycle and resonant frequency to achieve zero-current switching on or off of the switching devices; and it achieves energy transfer from the low-voltage DC side to the high-voltage DC side through a cascaded structure, using fewer power electronic devices and reducing hardware costs.

[0079] The following section provides a detailed description of the implementation of the resonant cavity of the resonant switched capacitor DC-DC converter, including the third LC resonant circuit, with reference to the accompanying drawings.

[0080] See Figure 9 The figure is a schematic diagram of a second type of DC-DC converter provided in an embodiment of this application.

[0081] The resonant cavity of the resonant switched capacitor DC-DC converter 500 for the DC fan provided in this application embodiment includes a fifth diode D5, a sixth diode D6, and a third LC resonant circuit; the third LC resonant circuit includes a first capacitor C, a resonant capacitor Cr, and a resonant inductor Lr.

[0082] The anode of the fifth diode D5 is connected to the cathode of the sixth diode D6. The first terminal of the first capacitor C is connected to the cathode of the fifth diode D5, and the second terminal of the first capacitor C is connected to the anode of the sixth diode D6. The first terminal of the resonant capacitor Cr and the resonant inductor Lr connected in series is connected to the cathode of the sixth diode D6, and the second terminal of the resonant capacitor Cr and the resonant inductor Lr connected in series is connected to the anode of the fifth diode D5 in the adjacent resonant cavity. The capacitance of the resonant capacitor Cr and the capacitance of the first capacitor C are on the same order of magnitude, causing the voltage across the resonant capacitor Cr and the voltage across the first capacitor C to change periodically during resonance. Quantitatively, the fact that the capacitance of the resonant capacitor Cr and the capacitance of the first capacitor C are on the same order of magnitude satisfies the following relationship: the ratio of the maximum value to the minimum value of Cr and C is less than or equal to 10.

[0083] The resonant switched capacitor DC-DC converter 500 achieves zero-current switching of the first switch S1 and the second switch S2 by controlling the switching period and resonant frequency and utilizing the resonance of the third LC resonant circuit, thereby reducing losses. Since the third LC resonant circuit includes a first capacitor C and realizes the transfer of energy from the low-voltage DC side to the high-voltage DC side through a cascaded structure, it uses fewer power electronic devices and has lower hardware costs.

[0084] The resonant cavity of the DC fan provided in this application embodiment includes a fifth diode, a sixth diode, and a third LC resonant circuit; the third LC resonant circuit includes a first capacitor, a resonant capacitor, and a resonant inductor. The anode of the fifth diode is connected to the cathode of the sixth diode, the first terminal of the first capacitor is connected to the cathode of the fifth diode, and the second terminal of the first capacitor is connected to the anode of the sixth diode; the first terminal of the resonant capacitor and the resonant inductor connected in series is connected to the cathode of the sixth diode, and the second terminal of the resonant capacitor and the resonant inductor connected in series is connected to the anode of the fifth diode in an adjacent resonant cavity.

[0085] The DC fan provided in this application reduces losses by controlling the switching cycle and resonant frequency to achieve zero-current switching on or off of the switching devices. Since the third LC resonant circuit includes a first capacitor C and achieves energy transfer from the low-voltage DC side to the high-voltage DC side through a cascaded structure, fewer power electronic devices are used, resulting in lower hardware costs.

[0086] The DC fan provided in this application embodiment also includes an auxiliary power supply device connected in parallel to the output terminal of the resonant switched capacitor DC converter. The auxiliary power supply device provides power for the start-up of the DC fan and the auxiliary system. This application does not limit the type of auxiliary power supply device. For example, it can be a DC / DC converter or a DC / AC converter.

[0087] Based on the DC wind turbine provided in the above embodiments, this application also provides a wind turbine generator set, including the DC wind turbine described in the above embodiments, which can directly output DC power and transmit electrical energy through DC cables. This application does not specifically limit the specific application scenario; for example, it can be used for offshore wind power generation or onshore wind power generation.

[0088] The wind turbine generator set provided in this application embodiment uses a DC wind turbine with a simple structure, low cost, and low loss, which reduces the cost of the wind turbine generator set.

[0089] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0090] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A direct current fan characterized by, include: Blades, gearboxes, generators, and rectifiers; The blades are connected to a gearbox, and the gearbox is connected to the rotor in the generator; The rotor winding of the generator is connected to the input terminal of the rectifier; The rectifier includes at least three bridge arms, with the midpoint of each bridge arm connected to the corresponding phase of the rotor winding. Each upper bridge arm includes a first multilevel converter, a first diode, and a second diode; each lower bridge arm includes a second multilevel converter, a third diode, and a fourth diode. The first terminal of the first multilevel converter is connected to the anode of the first diode, and the cathode of the first diode is connected to the positive output terminal of the rectifier; the second terminal of the first multilevel converter is connected to the midpoint of the bridge arm; the cathode of the second diode is connected to the anode of the first diode, and the anode of the second diode is connected to the common neutral point; The first end of the second multilevel converter is connected to the midpoint of the bridge arm; the second end of the second multilevel converter is connected to the anode of the third diode, and the cathode of the third diode is connected to the common neutral point; the cathode of the fourth diode is connected to the anode of the third diode, and the anode of the fourth diode is connected to the negative output terminal of the rectifier.

2. The direct current fan of claim 1, wherein Both the first multilevel converter and the second multilevel converter include: a bridge arm inductor and multiple sub-modules connected in series; The submodule includes a full-bridge circuit or a half-bridge circuit.

3. The DC fan according to claim 1 or 2, characterized in that, Also includes: Resonant switched capacitor DC-DC converter; The input terminal of the resonant switched capacitor DC-DC converter is connected to the output terminal of the rectifier, and is used to boost the output voltage of the rectifier before outputting it.

4. The DC fan according to claim 3, characterized in that, The resonant switched capacitor DC-DC converter includes: a first switching transistor, a second switching transistor, a first resonant branch, and a second resonant branch; The first end of the first switching transistor is connected to the positive output terminal of the rectifier, the second end of the first switching transistor is connected to the first end of the second switching transistor, and the second end of the second switching transistor is connected to the negative output terminal of the rectifier. The first end of the first resonant branch is connected to the first end of the first switching transistor, and the second end of the first resonant branch serves as the positive output terminal of the resonant switched capacitor DC-DC converter. The first end of the second resonant branch is connected to the second end of the second switching transistor, and the second end of the second resonant branch serves as the negative output terminal of the resonant switched capacitor DC-DC converter. Both the first resonant branch and the second resonant branch include multiple resonant cavities connected in series.

5. The DC fan according to claim 4, characterized in that, The resonant cavity includes: a fifth diode, a sixth diode, a first LC resonant circuit, and a second LC resonant circuit; both the first LC resonant circuit and the second LC resonant circuit include a resonant capacitor and a resonant inductor connected in series. The anode of the fifth diode is connected to the cathode of the sixth diode; the first terminal and the second terminal of the first LC resonant circuit are respectively connected to the cathode of the fifth diode and the anode of the sixth diode; the first terminal of the second LC resonant circuit is connected to the cathode of the sixth diode, and the second terminal of the second LC resonant circuit is connected to the anode of the fifth diode in the adjacent resonant cavity; Both the resonant capacitor in the first LC resonant circuit and the resonant capacitor in the second LC resonant circuit are periodically charged and discharged during the switching cycle of the resonant switched capacitor DC-DC converter. The energy of the resonant capacitor in the first LC resonant circuit and the resonant capacitor in the second LC resonant circuit during charging and discharging participates in the resonant energy transfer through the resonant inductor in the first LC resonant circuit and the resonant inductor in the second LC resonant circuit, respectively.

6. The DC fan according to claim 4, characterized in that, The resonant cavity includes: a fifth diode, a sixth diode, and a third LC resonant circuit; the third LC resonant circuit includes a first capacitor, a resonant capacitor, and a resonant inductor. The anode of the fifth diode is connected to the cathode of the sixth diode, the first terminal of the first capacitor is connected to the cathode of the fifth diode, and the second terminal of the first capacitor is connected to the anode of the sixth diode. The first end of the series connection between the resonant capacitor and the resonant inductor is connected to the cathode of the sixth diode, and the second end of the series connection between the resonant capacitor and the resonant inductor is connected to the anode of the fifth diode in the adjacent resonant cavity. The capacitance value of the resonant capacitor and the capacitance value of the first capacitor are on the same order of magnitude, so that the voltage across the resonant capacitor and the voltage across the first capacitor change periodically during the resonance process.

7. The DC fan according to any one of claims 1 to 6, characterized in that, The common neutral point is directly grounded.

8. The DC fan according to any one of claims 1 to 6, characterized in that, The common neutral point is grounded via impedance.

9. The DC fan according to any one of claims 1 to 6, characterized in that, The common neutral point is suspended.

10. A wind turbine generator set, characterized in that, Includes the DC fan as described in any one of claims 1 to 9.

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