Converter machine side common mode voltage suppression device and method, converter and fan

Abstract

The present invention provides a device and method for suppressing the common-mode voltage on the machine side of a converter, a converter and a wind turbine. The device includes: a rectifier module, a DC bus, a DC support capacitor, a controllable inverter module and an isolation transformer, wherein the rectifier module, the DC support capacitor, the controllable inverter module and the isolation transformer are arranged in sequence between the output end of the power generation equipment and the power grid; wherein the input end of the rectifier module is used to connect the output end of the power generation equipment, and the output end of the rectifier module is connected to the DC bus; the positive and negative electrodes of the DC support capacitor are respectively connected to the DC positive bus and the DC negative bus of the DC bus; the DC bus is connected to the primary side of the isolation transformer via the controllable inverter module, and the secondary side of the isolation transformer is connected to the power grid. According to the device and method, the converter and the wind turbine generator set, while suppressing the common-mode voltage on the machine side well, additional AC power can be fed to the power grid.

Description

Technical Field

[0001] The present invention generally relates to the field of electronic power technology, and more specifically, to a converter machine-side common-mode voltage suppression device and method, a converter and a wind turbine (ie, a wind turbine generator set). Background Art

[0002] At present, the main methods used are Figure 1 The RLC common-mode voltage filter circuit composed of a resistor R, an inductor L and a capacitor C shown in the figure is used to filter the common-mode voltage on the machine side of the converter to reduce the amplitude of the common-mode voltage on the machine side. However, this method of suppressing the common-mode voltage on the machine side is sensitive to the machine-side parameters of the converter, the parameters of the power generation equipment, and the cable length between the converter and the power generation equipment. Different RLC parameters need to be set for different power generation equipment, and the spikes of the high-frequency common-mode voltage on the machine side cannot be completely suppressed. In addition, this method of suppressing the common-mode voltage on the machine side ultimately converts the energy of the common-mode voltage on the machine side into heat and dissipates it, resulting in a large amount of heat generated by the RLC common-mode voltage filter circuit. Summary of the invention

[0003] An exemplary embodiment of the present invention is to provide a converter machine-side common-mode voltage suppression device and method, a converter and a wind turbine generator set, so as to reduce the dependence of suppressing the machine-side common-mode voltage on the selection of various device parameters and improve the applicability of the converter machine-side common-mode voltage suppression solution.

[0004] According to an exemplary embodiment of the present invention, a common-mode voltage suppression device for a converter machine side is provided, the device comprising: a rectifier module, a DC bus, a DC support capacitor, a controllable inverter module and an isolation transformer, wherein the rectifier module, the DC support capacitor, the controllable inverter module and the isolation transformer are sequentially arranged between the output end of the power generation equipment and the power grid; wherein the input end of the rectifier module is used to connect the output end of the power generation equipment, and the output end of the rectifier module is connected to the DC bus; the positive and negative electrodes of the DC support capacitor are respectively connected to the DC positive bus and the DC negative bus of the DC bus; the DC bus is connected to the primary side of the isolation transformer via the controllable inverter module, and the secondary side of the isolation transformer is connected to the power grid.

[0005] Optionally, the device further comprises: a pre-charging module, wherein the secondary side of the isolation transformer is connected to the power grid via the pre-charging module, and the pre-charging module obtains voltage from the power grid to pre-charge the DC bus.

[0006] Optionally, the rectifier module is an uncontrolled rectifier bridge, which includes: a first diode, a second diode, a third diode and a fourth diode, wherein the first diode and the second diode are connected in series between the DC positive bus and the DC negative bus; the third diode and the fourth diode are connected in series between the DC positive bus and the DC negative bus; the cathode of the first diode and the cathode of the third diode are connected to the DC positive bus, and the anode of the second diode and the anode of the fourth diode are connected to the DC negative bus; the anode of the first diode is connected to the output end of the power generation equipment, and the anode of the third diode is grounded.

[0007] Optionally, the controllable inverter module includes: a first insulated gate bipolar transistor, a second insulated gate bipolar transistor, a third insulated gate bipolar transistor, a fourth insulated gate bipolar transistor, a first freewheeling diode, a second freewheeling diode, a third freewheeling diode and a fourth freewheeling diode, wherein the collector of the first insulated gate bipolar transistor and the collector of the third insulated gate bipolar transistor are connected to the DC positive bus, the emitter of the second insulated gate bipolar transistor and the emitter of the fourth insulated gate bipolar transistor are connected to the DC negative bus, the emitter of the first insulated gate bipolar transistor and the collector of the second insulated gate bipolar transistor are connected to one end of the primary side of the isolation transformer, the emitter of the third insulated gate bipolar transistor and the collector of the fourth insulated gate bipolar transistor are connected to the other end of the primary side of the isolation transformer, wherein the first insulated gate bipolar transistor is connected in reverse parallel to the first freewheeling diode, the second insulated gate bipolar transistor is connected in reverse parallel to the second freewheeling diode, the third insulated gate bipolar transistor is connected in reverse parallel to the third freewheeling diode, and the fourth insulated gate bipolar transistor is connected in reverse parallel to the fourth freewheeling diode.

[0008] Optionally, the pre-charging module includes: a pre-charging contactor, a pre-charging resistor and a main contactor, wherein one end of the secondary side of the isolation transformer is connected to one end of the pre-charging contactor and one end of the main contactor, the other end of the main contact is connected to the power grid, and the other end of the pre-charging contactor is connected to the power grid via the pre-charging resistor.

[0009] According to another exemplary embodiment of the present invention, a converter is provided, wherein the converter includes the converter machine-side common-mode voltage suppression device as described above.

[0010] According to another exemplary embodiment of the present invention, a wind turbine generator set is provided, the wind turbine generator set comprising the converter as described above, the power generation device being a generator of the wind turbine generator set, the three-phase output end of the generator being connected to the input end of the converter.

[0011] According to another exemplary embodiment of the present invention, a method for suppressing common-mode voltage on the machine side of a converter is provided, and the method is applied to the common-mode voltage suppression device on the machine side of the converter as described above, and the method includes: when the converter is running to generate a machine-side common-mode voltage, rectifying the generated machine-side common-mode voltage into a DC voltage through a rectifier module, and outputting the rectified DC voltage to a DC bus, and boosting the voltage of the DC bus through a DC support capacitor; inverting the voltage of the DC bus into a single-phase AC voltage through a controllable inverter module; converting the single-phase AC voltage output by the controllable inverter module into an AC voltage that can be connected to a power grid through an isolation transformer and connecting the converted AC voltage to the power grid.

[0012] Optionally, the method further includes: before the converter starts running, obtaining voltage from the power grid through a pre-charging module to pre-charge the DC bus until the voltage of the DC bus reaches a preset value, and stopping pre-charging the DC bus.

[0013] Optionally, after the voltage of the DC bus reaches the preset value and the step of stopping precharging the DC bus is performed, the secondary side of the isolation transformer is directly connected to the power grid, and the controllable inverter module performs pulse width modulation to stabilize the voltage of the DC bus within a preset range.

[0014] According to the converter machine-side common-mode voltage suppression device and method of the exemplary embodiment of the present invention, by absorbing, storing, inverting the machine-side common-mode voltage, and finally converting it into AC power that can be connected to the power grid and fed into the power grid, it is possible to suppress the machine-side common-mode voltage well while increasing the power generation of the power generation equipment, improving the power generation efficiency of the power generation equipment, and reducing the heat generation; and it is not sensitive to the converter machine-side parameters, the power generation equipment parameters, and the cable length between the converter and the power generation equipment, so that it can be well adapted to different usage scenarios, thereby improving the applicability of the converter machine-side common-mode voltage suppression solution.

[0015] Additional aspects and / or advantages of the present general inventive concept will be set forth in part in the following description and in part will be obvious from the description, or may be learned through practice of the present general inventive concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects and features of the exemplary embodiments of the present invention will become more apparent through the following description in conjunction with the accompanying drawings which exemplarily illustrate the embodiments, in which:

[0017] Figure 1 An example of an existing RLC common mode voltage filtering circuit for filtering a machine side common mode voltage is shown;

[0018] Figure 2A schematic diagram showing a common-mode voltage suppression device on the machine side of a converter according to an exemplary embodiment of the present invention is shown;

[0019] Figure 3 A schematic diagram showing a common-mode voltage suppression device on the machine side of a converter according to another exemplary embodiment of the present invention is shown;

[0020] Figure 4 A circuit diagram showing a common-mode voltage suppression device on the machine side of a converter according to an exemplary embodiment of the present invention;

[0021] Figure 5 A flow chart showing a method for suppressing common-mode voltage on the machine side of a converter according to an exemplary embodiment of the present invention is shown;

[0022] Figure 6 A flow chart of a method for suppressing common-mode voltage on the machine side of a converter according to another exemplary embodiment of the present invention is shown. DETAILED DESCRIPTION

[0023] Reference will now be made in detail to embodiments of the present invention, examples of which are shown in the accompanying drawings, wherein like reference numerals refer to like parts throughout. The embodiments will be described below with reference to the drawings in order to explain the present invention.

[0024] Figure 2 A schematic diagram of a common-mode voltage suppression device on the machine side of a converter according to an exemplary embodiment of the present invention is shown.

[0025] like Figure 2 As shown, the converter machine-side common-mode voltage suppression device according to an exemplary embodiment of the present invention includes: a rectifier module 10, a DC bus 20, a DC support capacitor 30, a controllable inverter module 40, and an isolation transformer 50. The rectifier module 10, the DC support capacitor 30, the controllable inverter module 40, and the isolation transformer 50 are sequentially arranged between the output end of the power generation equipment and the power grid.

[0026] The input end of the rectifier module 10 is used to connect the output end of the power generation equipment, and the output end of the rectifier module 10 is connected to the DC bus 20; the positive and negative electrodes of the DC support capacitor 30 are respectively connected to the DC positive bus and the DC negative bus of the DC bus 20; the DC bus 20 is connected to the primary side of the isolation transformer 50 via the controllable inverter module 40, and the secondary side of the isolation transformer 50 is connected to the power grid. The rectifier module 10 rectifies the machine-side common-mode voltage generated when the converter is running into a DC voltage, and outputs the rectified DC voltage to the DC bus 20. The isolation transformer 50 transforms the single-phase AC voltage output by the controllable inverter module 40, connects the transformed AC voltage to the power grid, and isolates the common-mode voltage from the power grid.

[0027] As an example, the power generation device may be a generator of a wind turbine generator set. It should be understood that the power generation device may also be other types of power generation devices.

[0028] As an example, the input end of the rectifier module 10 can be connected to one of the three-phase output ends of the power generation equipment (ie, the A-phase output end, the B-phase output end and the C-phase output end), and the three-phase output end is connected to the input end of the converter.

[0029] exist Figure 2 In the example, only the input end of the rectifier module 10 is connected to the A-phase output end of the power generation equipment. Here, it should be understood that the input end of the rectifier module 10 can also be connected to the B-phase output end or the C-phase output end of the power generation equipment. In fact, three converter machine-side common-mode voltage suppression devices according to an exemplary embodiment of the present invention should be provided for one power generation equipment. The three-phase output ends of the power generation equipment correspond to these three converter machine-side common-mode voltage suppression devices one by one, and each phase output end is respectively connected to the corresponding converter machine-side common-mode voltage suppression device, thereby suppressing the corresponding machine-side common-mode voltages of the converter and the power generation equipment. In addition, Figure 2 The GND in the figure indicates ground.

[0030] Specifically, the rectifier module 10 is used to rectify the machine-side common-mode voltage generated when the converter is running into a DC voltage, and output the rectified DC voltage to the DC bus 20 .

[0031] As an example, the rectifier module 10 may be an uncontrolled rectifier bridge including four diodes.

[0032] As an example, the diode may be a silicon carbide diode. Considering that the frequency of the common-mode voltage on the machine side of the converter is high and the voltage change rate is large, according to an exemplary embodiment of the present invention, a silicon carbide diode with high withstand voltage and short reverse recovery time may be used to realize the uncontrolled rectification function of the common-mode voltage on the machine side with high frequency and large voltage change rate, thereby being able to well suppress the peak of the high-frequency common-mode voltage on the machine side and improve the absorption effect of the common-mode voltage on the machine side.

[0033] The DC support capacitor 30 is used to store energy for the DC voltage output by the rectifier module 10 to increase the DC voltage of the DC bus 20 , that is, the DC support capacitor 30 is used to boost the voltage of the DC bus 20 to stabilize the voltage of the DC bus 20 .

[0034] As an example, the DC support capacitor 30 may be a thin film capacitor with a relatively high withstand voltage.

[0035] The controllable inverter module 40 is used to stabilize the voltage of the DC bus 20 within a preset range and invert the DC voltage of the DC bus 20 into a single-phase AC voltage, that is, to convert the DC energy of the DC bus 20 into AC energy.

[0036] As an example, the controllable inverter module 40 may include four insulated gate bipolar transistors (IGBTs) or metal-oxide semiconductor field effect transistors (MOSFETs).

[0037] The isolation transformer 50 is used to convert the single-phase AC voltage output by the controllable inverter module 40 into an AC voltage that can be connected to the power grid and connect the converted AC voltage to the power grid, and isolate the machine-side common-mode voltage from the power grid to prevent the machine-side common-mode voltage from interfering with the power grid.

[0038] As an example, the isolation transformer 50 can convert the AC voltage output by the controllable inverter module 40 into an AC voltage of 230V and connect it to the power grid to feed the AC energy into the power grid.

[0039] According to the converter machine-side common-mode voltage suppression device of an exemplary embodiment of the present invention, the energy of the machine-side common-mode voltage is transferred from between the converter and the ground through the rectifier module 10, the DC support capacitor 30, the controllable inverter module 40, and the isolation transformer 50, and finally flows into the power grid, thereby effectively suppressing the machine-side common-mode voltage and increasing the power generation of the wind turbine generator set.

[0040] The converter machine side common mode voltage suppression device according to the exemplary embodiment of the present invention is small in size, light in weight, and generates less heat than the existing RLC common mode voltage filter circuit, and has a good absorption capacity for the energy of the machine side common mode voltage, and can additionally increase the power generation of the power generation equipment. The converter machine side common mode voltage suppression device according to the exemplary embodiment of the present invention can be applied to the power generation equipment with the machine side common mode voltage exceeding the standard as a supplement to the RLC common mode voltage filter circuit, and can also be applied in the design of new power generation equipment.

[0041] Figure 3 A block diagram of a common-mode voltage suppression device on the machine side of a converter according to another exemplary embodiment of the present invention is shown.

[0042] like Figure 3 As shown, the common-mode voltage suppression device on the machine side of the converter according to an exemplary embodiment of the present invention includes: a rectifier module 10, a DC bus 20, a DC support capacitor 30, a controllable inverter module 40, an isolation transformer 50, and a pre-charging module 60.

[0043] The connection method and specific implementation method between the rectifier module 10, the DC bus 20, the DC support capacitor 30, the controllable inverter module 40 and the isolation transformer 50 can refer to the above combination Figure 2The specific implementation method described is implemented and will not be repeated here.

[0044] The secondary side of the isolation transformer 50 is connected to the power grid via the pre-charging module 60 , and the pre-charging module 60 obtains voltage from the power grid to pre-charge the DC bus 20 .

[0045] As an example, the pre-charging module 60 is used to slowly charge the DC bus 20 before the inverter machine side is started to establish the voltage of the DC bus 20, thereby avoiding the impact of the inverter machine side startup on the DC support capacitor 30.

[0046] Figure 4 A circuit diagram of a common-mode voltage suppression device on the machine side of a converter according to an exemplary embodiment of the present invention is shown.

[0047] like Figure 4 As shown, as an example, the rectifier module 10 may include: a first diode 101, a second diode 103, a third diode 103 and a fourth diode 104, wherein the first diode 101 and the second diode 102 are connected in series between the DC positive bus 201 and the DC negative bus 202 of the DC bus 20; the third diode 103 and the fourth diode 104 are connected in series between the DC positive bus 201 and the DC negative bus 202; the cathode (i.e., K pole) of the first diode 101 and the cathode of the third diode 103 are connected to the DC positive bus, and the anode (i.e., A pole) of the second diode 102 and the anode of the fourth diode 104 are connected to the DC negative bus; the anode of the first diode 101 is connected to the output end of the power generation equipment, and the anode of the third diode 103 is grounded.

[0048] As an example, the controllable inverter module 40 may include: a first insulated gate bipolar transistor 401, a second insulated gate bipolar transistor 402, a third insulated gate bipolar transistor 403, a fourth insulated gate bipolar transistor 404, a first freewheeling diode 405, a second freewheeling diode 406, a third freewheeling diode 407 and a fourth freewheeling diode 408, wherein the collector (i.e., C pole) of the first insulated gate bipolar transistor 401 and the collector of the third insulated gate bipolar transistor 403 are connected to the DC positive bus 201, the emitter (i.e., E pole) of the second insulated gate bipolar transistor 402 and the emitter of the fourth insulated gate bipolar transistor 404 are connected to the DC negative bus 202, and the first insulated gate bipolar transistor The emitter of 401 and the collector of the second insulated gate bipolar transistor 402 are connected to one end of the primary side of the isolation transformer 50 (i.e., pin 1 of the isolation transformer 50), the emitter of the third insulated gate bipolar transistor 403 and the collector of the fourth insulated gate bipolar transistor 404 are connected to the other end of the primary side of the isolation transformer 50 (i.e., pin 2 of the isolation transformer 50), the first insulated gate bipolar transistor 401 is connected in reverse parallel to the first freewheeling diode 405, the second insulated gate bipolar transistor 402 is connected in reverse parallel to the second freewheeling diode 406, the third insulated gate bipolar transistor 403 is connected in reverse parallel to the third freewheeling diode 407, and the fourth insulated gate bipolar transistor 404 is connected in reverse parallel to the fourth freewheeling diode 408.

[0049] As an example, the pre-charging module 60 may include: a pre-charging contactor 601, a pre-charging resistor 602 and a main contactor 603, wherein one end of the secondary side of the isolation transformer 50 (i.e., pin 3 of the isolation transformer 50) is connected to one end of the pre-charging contactor 601 (i.e., pin 1 of the pre-charging contactor 601) and one end of the main contactor 603 (i.e., pin 1 of the main contactor 603), the other end of the main contactor 603 (i.e., pin 2 of the main contactor 603) is connected to the power grid, and the other end of the pre-charging contactor 601 (i.e., pin 2 of the pre-charging contactor 601) is connected to the power grid via the pre-charging resistor 602.

[0050] Here, when the DC bus 20 needs to be pre-charged, the pre-charging contactor 601 is closed and the main contactor 603 is opened; when the pre-charging is completed, the pre-charging contactor 601 is opened and the main contactor 603 is closed.

[0051] An exemplary embodiment of the present invention further provides a converter, wherein the converter includes the converter machine-side common-mode voltage suppression device as described in the above exemplary embodiment.

[0052] An exemplary embodiment of the present invention further provides a wind turbine generator set, which includes a converter as described in the above exemplary embodiment, wherein the power generation equipment is a generator of the wind turbine generator set, and a three-phase output end of the generator is connected to an input end of the converter.

[0053] Figure 5 A flowchart of a method for suppressing common-mode voltage on the machine side of a converter according to an exemplary embodiment of the present invention is shown. Here, the method is applied to the common-mode voltage suppression device on the machine side of a converter as described in the exemplary embodiment above.

[0054] In S10 , when the converter generates a machine-side common-mode voltage during operation, the generated machine-side common-mode voltage is rectified into a DC voltage through the rectifier module 10 , and the rectified DC voltage is output to the DC bus 20 , and the voltage of the DC bus 20 is boosted through the DC support capacitor 30 .

[0055] In S20 , the voltage of the DC bus 20 is inverted into a single-phase AC voltage by the controllable inverter module 40 .

[0056] In S30, the single-phase AC voltage output by the controllable inverter module 40 is converted into an AC voltage that can be connected to the power grid by the isolation transformer 50, and the converted AC voltage is connected to the power grid. Here, in the process of executing the common-mode voltage suppression method on the machine side of the converter according to the exemplary embodiment of the present invention, the isolation transformer 50 can also isolate the common-mode voltage from the power grid.

[0057] As an example, the method for suppressing the common-mode voltage on the machine side of the converter according to the exemplary embodiment of the present invention may further include: before the converter starts to operate, obtaining voltage from the power grid through the pre-charging module 60 to pre-charge the DC bus 20 until the voltage of the DC bus 20 reaches a preset value, and stopping pre-charging the DC bus 20. For example, the preset value may be 720V.

[0058] As an example, after the voltage of the DC bus 20 reaches the preset value and the step of precharging the DC bus 20 is stopped, the secondary side of the isolation transformer 50 is directly connected to the grid, and the controllable inverter module 40 performs pulse width modulation (PWM) to stabilize the voltage of the DC bus 20 within a preset range. For example, pulse width modulation can be used to control the IGBT or MOSFET of the controllable inverter module 40 to stabilize the voltage of the DC bus 20 within the preset range.

[0059] Figure 6 A flow chart of a method for suppressing common-mode voltage on the machine side of a converter according to another exemplary embodiment of the present invention is shown.

[0060] Reference Figure 6In S101, after the converter machine-side common-mode voltage suppression device according to the exemplary embodiment of the present invention is powered on, an initialization process is entered.

[0061] In S102 , after the self-test passes, the pre-charging contactor 601 of the pre-charging module 60 is controlled to be closed and the main contactor 603 is opened, so as to charge the DC bus 20 through the pre-charging resistor 602 , the isolation transformer 50 and the controllable inverter module 40 .

[0062] In S103, the voltage U of the DC bus 20 is detected. d Whether the preset value is reached.

[0063] In S104, when it is detected that the voltage of the DC bus 20 reaches the preset value, the pre-charging contactor 601 of the pre-charging module 60 is controlled to be disconnected and the main contactor 603 is controlled to be closed. d When the preset value cannot be reached, S105 is executed to notify the fault.

[0064] In S106 , after the main contactor 603 is closed, the controllable inverter module 40 performs PWM modulation to stabilize the voltage of the DC bus 20 within the preset range.

[0065] In S107, the machine side of the converter is started.

[0066] In S108 and S109 , when the machine side of the converter is started and a machine side common mode voltage is generated, the common mode voltage is rectified into a direct current through the rectifier module 10 , and energy is stored through the direct current support capacitor 30 .

[0067] In S110, when the controllable inverter module 40 detects that the voltage of the DC bus 20 increases due to the energy storage of the DC support capacitor 30, the voltage of the DC bus 20 can be closed-loop controlled to control the voltage of the DC bus 20 within the preset range, and the DC voltage of the DC bus 20 is converted into an AC voltage.

[0068] In S111 and S112 , the single-phase AC voltage output by the controllable inverter module 40 is stepped down and isolated by the isolation transformer 50 , and finally connected to the power grid.

[0069] Although some exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that modifications may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A common mode voltage suppression device for a converter, characterized in that: The device comprises: a rectifier module, a DC bus, a DC support capacitor, a controllable inverter module and an isolation transformer, wherein the rectifier module, the DC support capacitor, the controllable inverter module and the isolation transformer are sequentially arranged between the output end of the power generation equipment and the power grid; The input end of the rectifier module is used to connect to the output end of the power generation equipment, and the output end of the rectifier module is connected to the DC bus; The positive electrode and negative electrode of the DC support capacitor are respectively connected to the DC positive bus and the DC negative bus of the DC bus; The DC bus is connected to the primary side of the isolation transformer via a controllable inverter module, and the secondary side of the isolation transformer is connected to the power grid.

2. The device according to claim 1, characterized in that The device further comprises: a pre-charging module, The secondary side of the isolation transformer is connected to the power grid via a pre-charging module, and the pre-charging module obtains voltage from the power grid to pre-charge the DC bus.

3. The device according to claim 1 or 2, characterized in that: The rectifier module is an uncontrolled rectifier bridge, which includes: a first diode, a second diode, a third diode and a fourth diode. The first diode and the second diode are connected in series between the DC positive bus and the DC negative bus; the third diode and the fourth diode are connected in series between the DC positive bus and the DC negative bus; the cathode of the first diode and the cathode of the third diode are connected to the DC positive bus, and the anode of the second diode and the anode of the fourth diode are connected to the DC negative bus; An anode of the first diode is connected to the output end of the power generation device, and an anode of the third diode is grounded.

4. The device according to claim 1 or 2, characterized in that: The controllable inverter module includes: a first insulated gate bipolar transistor, a second insulated gate bipolar transistor, a third insulated gate bipolar transistor, a fourth insulated gate bipolar transistor, a first freewheeling diode, a second freewheeling diode, a third freewheeling diode and a fourth freewheeling diode, The collector of the first insulated gate bipolar transistor and the collector of the third insulated gate bipolar transistor are connected to the DC positive bus, and the emitter of the second insulated gate bipolar transistor and the emitter of the fourth insulated gate bipolar transistor are connected to the DC negative bus. The emitter of the first insulated gate bipolar transistor and the collector of the second insulated gate bipolar transistor are connected to one end of the primary side of the isolation transformer, and the emitter of the third insulated gate bipolar transistor and the collector of the fourth insulated gate bipolar transistor are connected to the other end of the primary side of the isolation transformer. Among them, the first insulated gate bipolar transistor is connected in reverse parallel to the first freewheeling diode, the second insulated gate bipolar transistor is connected in reverse parallel to the second freewheeling diode, the third insulated gate bipolar transistor is connected in reverse parallel to the third freewheeling diode, and the fourth insulated gate bipolar transistor is connected in reverse parallel to the fourth freewheeling diode.

5. The device according to claim 2, characterized in that The pre-charging module includes: a pre-charging contactor, a pre-charging resistor and a main contactor. One end of the secondary side of the isolation transformer is connected to one end of the pre-charging contactor and one end of the main contactor, the other end of the main contactor is connected to the power grid, and the other end of the pre-charging contactor is connected to the power grid via the pre-charging resistor.

6. A converter, characterized in that: The converter comprises the converter machine-side common-mode voltage suppression device according to any one of claims 1 to 5.

7. A wind turbine generator set, characterized in that: The wind turbine generator set comprises the converter according to claim 6, the power generation equipment is a generator of the wind turbine generator set, and the three-phase output end of the generator is connected to the input end of the converter.

8. A method for suppressing common-mode voltage on the machine side of a converter, characterized in that: The method is applied to the converter machine-side common-mode voltage suppression device according to any one of claims 1 to 5, and the method comprises: When the converter is running and generates a machine-side common-mode voltage, the generated machine-side common-mode voltage is rectified into a DC voltage through the rectifier module, and the rectified DC voltage is output to the DC bus, and the voltage of the DC bus is boosted through the DC support capacitor; The voltage of the DC bus is inverted into a single-phase AC voltage through a controllable inverter module; The single-phase AC voltage output by the controllable inverter module is converted into an AC voltage that can be connected to the power grid through an isolation transformer, and the converted AC voltage is connected to the power grid.

9. The method according to claim 8, characterized in that The method further comprises: Before the converter starts to operate, a voltage is obtained from the power grid through a pre-charging module to pre-charge the DC bus until the voltage of the DC bus reaches a preset value, and then the pre-charging of the DC bus is stopped.

10. The method according to claim 9, characterized in that After the voltage of the DC bus reaches the preset value and the step of precharging the DC bus is stopped, the secondary side of the isolation transformer is directly connected to the power grid, and the controllable inverter module performs pulse width modulation to stabilize the voltage of the DC bus within a preset range.

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