Power converter powered by alternating current, motor and fan of pneumatic pipe network

Abstract

The invention discloses an AC power supply power converter, a motor and a fan of a pneumatic pipe network. The AC power supply power converter comprises a transformer, 3n rectification circuits and a three-phase cascade H-bridge circuit, the transformer comprises a primary winding and 3n secondary windings; the 3n secondary windings and the 3n rectifying circuits are in one-to-one correspondence; the primary winding is used for being connected with alternating current, and the input ends of the 3n rectifying circuits are used for being connected with the corresponding secondary windings; each phase of cascaded H-bridge circuit comprises n H-bridge inverter circuits, and n is an integer greater than or equal to 2; the rectification circuits and the inversion circuits are in one-to-one correspondence, and the input end of each H-bridge inversion circuit is connected with the output end of the corresponding rectification circuit; the output ends of the n H-bridge inverter circuits are connected in series, and each phase of cascaded H-bridge circuit is used for supplying power to one phase of the three-phase load. The technical scheme can solve the problem of insufficient withstand voltage of the switching tube, and can be applied to a scene with high input voltage.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to an AC-powered power converter, a motor, and a fan for a pneumatic pipe network. Background Art

[0002] At present, power converters are used in more and more scenarios, and the input voltage in some scenarios is relatively high. For example, the input voltage of the fan in the pneumatic pipe network has reached 3300 V. Therefore, it brings challenges to the withstand voltage of the switch tube in the power converter. The higher the withstand voltage, the higher the cost of the switch tube and the slower the response speed. Summary of the invention

[0003] In view of this, the present application provides an AC-powered power converter, a motor, and a fan for a pneumatic pipe network, which can solve the problem of insufficient voltage resistance of the switching tube and can be used in scenarios with high input voltage.

[0004] The present application provides an AC power converter, comprising: a transformer, 3n rectifier circuits and a three-phase cascade H-bridge circuit; the transformer comprises a primary winding and 3n secondary windings; the 3n secondary windings correspond to the 3n rectifier circuits one by one;

[0005] The primary winding is used to connect to alternating current, and the input ends of the 3n rectifier circuits are used to connect to the corresponding secondary windings;

[0006] Each phase cascade H-bridge circuit includes n H-bridge inverter circuits, where n is an integer greater than or equal to 2; the rectifier circuit and the inverter circuit correspond one to one, and the input end of each H-bridge inverter circuit is connected to the output end of the corresponding rectifier circuit; the output ends of the n H-bridge inverter circuits are connected in series, and each phase cascade H-bridge circuit is used to power one phase of a three-phase load.

[0007] In a possible implementation, there is one transformer, and the transformer includes a primary winding and 3n secondary windings.

[0008] In a possible implementation, there are 3n transformers, each of which includes a primary winding and a secondary winding; the primary winding of each transformer is connected in parallel to connect the alternating current, and the secondary winding of each transformer is connected to a corresponding rectifier circuit.

[0009] In a possible implementation manner, the rectifier circuit is a voltage-type rectifier.

[0010] In a possible implementation, the rectifier circuit includes a three-phase active midpoint clamped three-level bridge arm;

[0011] The input end of the three-phase active midpoint clamped three-level bridge arm is connected to the corresponding secondary winding through an inductor, and the output end of the three-phase active midpoint clamped three-level bridge arm is connected to the input end of the corresponding H-bridge inverter circuit.

[0012] In a possible implementation, the H-bridge inverter circuit includes two bridge arms connected in parallel, each bridge arm includes two switch tubes connected in series; the midpoint of the two bridge arms serves as the output end of the H-bridge inverter circuit.

[0013] In a possible implementation, the H-bridge inverter circuit includes two parallel-connected passive mid-point clamped three-level bridge arms or two parallel-connected active mid-point clamped three-level bridge arms.

[0014] In a possible implementation, the transformer is a multi-split winding transformer, and the voltage of the alternating current connected to the input end of the transformer is greater than or equal to 10 kV.

[0015] The present application also provides an electric motor, comprising a three-phase winding and the AC-powered power converter described above, wherein the AC-powered power converter is used to supply power to the three-phase winding.

[0016] The present application also provides a fan for a pneumatic pipe network, comprising a three-phase winding and the AC-powered power converter described above, wherein the AC-powered power converter is used to supply power to the three-phase winding.

[0017] The AC power supply power converter provided by the embodiment of the present application first uses a transformer to electrically isolate the primary and secondary sides, and multiple secondary windings are respectively connected to an independent rectifier circuit to divide the voltage, that is, multiple secondary windings share the overall AC voltage, and the higher input voltage is divided into independent multiple AC source outputs. The multiple AC sources are independent of each other, and the multiple DC sources are respectively input into multiple cascaded inverter circuits at the output ends, each phase includes multiple cascaded inverter circuits, and the multiple cascaded inverter circuits serve as one phase to supply power to one phase of the load, such as a three-phase load, corresponding to a three-phase cascaded inverter circuit. This can be applied to higher voltage AC power supply scenarios. Since multiple circuits in the power converter are connected in series, the voltage borne by the switch tube in a single circuit is relatively low, so the selection of the switch tube can reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of an AC power converter provided in an embodiment of the present application;

[0019] Figure 2 A schematic diagram of another AC-powered power converter provided in an embodiment of the present application;

[0020] Figure 3 A schematic diagram of a rectifier circuit provided in an embodiment of the present application;

[0021] Figure 4 A schematic diagram of a three-phase inverter circuit provided in an embodiment of the present application;

[0022] Figure 5 A schematic diagram of a VSR circuit provided in an embodiment of the present application;

[0023] Figure 6 A schematic diagram of a CHB circuit provided in an embodiment of the present application;

[0024] Figure 7 A schematic diagram of another CHB circuit provided in an embodiment of the present application;

[0025] Figure 8 A schematic diagram of a motor provided in an embodiment of the present application;

[0026] Fig. 9 A schematic diagram of a fan for a pneumatic pipe network provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0028] The embodiments of the present application do not specifically limit the application scenarios of the AC power converter. For example, the voltage level of the AC source of the AC power supply can reach several kilovolts or more than ten kilovolts, or even higher. For example, it can be 10kV. The power converter can be used in large motor or fan scenarios. For example, the load can be a motor in a coal mining machine in a coal mine, or a fan in a pneumatic pipe network.

[0029] See also Figure 1 , which is a schematic diagram of an AC power supply converter provided in an embodiment of the present application.

[0030] An embodiment of the present application provides an AC-powered power converter, comprising: a transformer T1, 3n rectifier circuits and a three-phase cascaded H-bridge circuit; the transformer T1 comprises a primary winding and 3n secondary windings; the 3n secondary windings correspond one to one with the 3n rectifier circuits.

[0031] The primary winding is used to connect to the alternating current, and the input ends of the 3n rectifier circuits are used to connect to the corresponding secondary windings.

[0032] Each phase cascade H-bridge circuit includes n H-bridge inverter circuits, where n is an integer greater than or equal to 2; the rectifier circuits and the inverter circuits correspond one to one, and the input end of each H-bridge inverter circuit is connected to the output end of the corresponding rectifier circuit; the output ends of the n H-bridge inverter circuits are connected in series, and each phase cascade H-bridge circuit is used to power one phase of the three-phase load.

[0033] The embodiment of the present application does not specifically limit the value of n, as long as it is an integer greater than or equal to 2. For example, when n is 2, Figure 1 As shown, each phase cascade H-bridge circuit in the AC power supply power converter includes 2 H-bridge inverter circuits, and correspondingly, includes 6 rectifier circuits. The 6 rectifiers are rectifier circuits P1 to P6. Each phase includes 2 inverter circuits, that is, the U phase includes an inverter circuit 20 and an inverter circuit 21, the V phase includes an inverter circuit 22 and an inverter circuit 23, and the W phase includes an inverter circuit 24 and an inverter circuit 25. The three-phase AC output terminals MU, MV and MW of the power converter are connected to the motor M to power the motor M.

[0034] The embodiment of the present application does not specifically limit the number of transformers included in the AC power converter, which may be one or more. Figure 1 A transformer T1 is taken as an example for introduction. The transformer T1 includes a primary winding and 3n secondary windings. Figure 1 In the example, n is 2, that is, the transformer T1 includes 6 secondary windings, each of which includes three phases, namely U1, V1 and W1 to UU6, V6 and W6. In a possible implementation, the transformer is a multi-split winding transformer, and the voltage of the AC power connected to the input end of the transformer is greater than or equal to 10kV.

[0035] The input ends of the six rectifier circuits are respectively connected to the six secondary windings, and the rectifier circuits are used to rectify the alternating current output by the secondary windings into direct current and output it to the inverter circuit. The two output ends of the first rectifier circuit P1 are Vdc1+ and Vdc1-, respectively. The two output ends of the second rectifier circuit P2 are Vdc2+ and Vdc2-, respectively. The two output ends of the third rectifier circuit P3 are Vdc3+ and Vdc3-, respectively. The two output ends of the fourth rectifier circuit P4 are Vdc4+ and Vdc4-, respectively. The two output ends of the fifth rectifier circuit P5 are Vdc5+ and Vdc5-, respectively. The two output ends of the sixth rectifier circuit P6 are Vdc6+ and Vdc6-, respectively.

[0036] In a possible implementation, the transformers may be multiple independent ones, for example, 3n transformers, each transformer including a primary winding and a secondary winding; the primary windings of the 3n transformers are connected in parallel to connect the AC power, and the secondary winding of each transformer is connected to the corresponding rectifier circuit, that is, the input end of a rectifier circuit corresponds to the secondary winding of an independent transformer. For example, six rectifier circuits correspond to six independent transformers.

[0037] The following describes the implementation method of the corresponding power converter when n is 3 in conjunction with the accompanying drawings.

[0038] See also Figure 2, which is a schematic diagram of another AC-powered power converter provided in an embodiment of the present application.

[0039] When n is 3, each phase of the cascaded H-bridge circuit in the AC power supply power converter includes 3 H-bridge inverter circuits, that is, each phase includes 3 inverter circuits. Correspondingly, the power converter includes 9 rectifier circuits, namely P1-P9. For example, when the AC power is 10kV, the power converter includes 9 rectifier circuits, and the voltage borne by the input end of each rectifier circuit is approximately 1100, so that the output voltage of the rectifier circuit is approximately 1500V, and the output voltage of the 3 H-bridge inverter circuits connected in series is approximately 3300V. The 3300V AC voltage is provided to the fan or motor, thereby meeting the power supply requirements of the high-voltage fan.

[0040] like Figure 2 As shown, each phase cascade H-bridge circuit in the AC power supply power converter includes three H-bridge inverter circuits, and correspondingly, includes nine rectifier circuits. The nine rectifier circuits are rectifier circuit P1 to DC / DC circuit P9. Each phase includes three inverter circuits, that is, the U phase includes inverter circuit 20, inverter circuit 21 and inverter circuit 22, the V phase includes inverter circuit 23, inverter circuit 24 and inverter circuit 25, and the W phase includes inverter circuit 26, inverter circuit 27 and inverter circuit 28. The three-phase AC output terminals MU, MV and MW of the power converter are connected to the motor M to supply power to the motor M.

[0041] Figure 3 Compare Figure 2 There are three more rectifier circuits, namely: the two output ends of the seventh rectifier circuit P7 are Vdc7+ and Vdc7-, the two output ends of the eighth rectifier circuit P8 are Vdc8+ and Vdc8-, and the two output ends of the ninth rectifier circuit P9 are Vdc9+ and Vdc9-.

[0042] It should be understood that the value of n can be adjusted according to the magnitude of the DC voltage, as long as the withstand voltage of the switch tubes in each circuit is met. For example, the switch tube can be an insulated gate bipolar transistor (IGBT, Insulated Gate Bipolar Transistor) or the like.

[0043] The AC power supply power converter provided by the embodiment of the present application first uses a transformer to electrically isolate the primary and secondary sides, and multiple secondary windings are respectively connected to an independent rectifier circuit to divide the voltage, that is, multiple secondary windings share the overall AC voltage, and the higher input voltage is divided into independent multiple AC source outputs. The multiple AC sources are independent of each other, and the multiple DC sources are respectively input into multiple cascaded inverter circuits at the output ends, each phase includes multiple cascaded inverter circuits, and the multiple cascaded inverter circuits serve as one phase to supply power to one phase of the load, such as a three-phase load, corresponding to a three-phase cascaded inverter circuit. This can be applied to higher voltage AC power supply scenarios. Since multiple circuits in the power converter are connected in series, the voltage borne by the switch tube in a single circuit is relatively low, so the selection of the switch tube can reduce costs.

[0044] The embodiment of the present application does not specifically limit the topology of the rectifier circuit. For example, it can be implemented using a voltage source rectifier (VSR, Voltage Source Rectifier).

[0045] See also Figure 3 , which is a schematic diagram of a rectifier circuit provided in an embodiment of the present application.

[0046] The embodiment of the present application continues to introduce the power converter including a transformer T1 as an example, the rectifier circuit is VSR, and taking n as 3 as an example, it corresponds to 9 VSRs, namely P1-P9.

[0047] See also Figure 4 , which is a schematic diagram of a three-phase inverter circuit provided in an embodiment of the present application.

[0048] In the embodiment of the present application, an example is given in which each phase inverter circuit includes a cascaded H-bridge (CHB) circuit.

[0049] Figure 4 and Figure 3 Correspondingly, the case where n is 3 is taken as an example for introduction. Figure 3 The three rectifier circuits in are respectively connected to the three CHBs in one phase, and the three CHBs of the U phase are Ma1, Ma2 and Ma3. The three CHBs of the V phase are Mb1, Mb2 and Mb3. The three CHBs of the W phase are Mac1, Mc2 and Mc3. Taking the U phase as an example, the first output terminal L1 of Ma1 serves as the positive output terminal of the U phase, that is, L1 of Ma1 is connected to MU, the second output terminal L2 of Ma1 is connected to L1 of Ma2, and L2 of Ma2 is connected to L1 of Ma3. Similarly, the connection relationship between the V phase and the W phase can refer to the description of the U phase, which will not be repeated here.

[0050] Figure 3 P1, P2 and P3 in are connected to Ma1, Ma2 and Ma3 of U phase respectively. Figure 3 P4, P5 and P6 are connected to Mb1, Mb2 and Mb3 of V phase respectively. Figure 3 P7, P8 and P9 in are connected to Mac1, Mc2 and Mc3 of W phase respectively.

[0051] The output ends of the three CHBs of each phase are connected in series as one phase, that is, the output ends of the three phases are MU, MV and MW respectively. The other ends of the three-phase CHBs are connected together, that is, star connection, such as Figure 4 As shown, L2 of Ma3, L2 of Mb3 and L2 of Mc3 are connected together.

[0052] pass Figure 4 It can be seen that the input end of the CHB provided in the embodiment of the present application is an independent DC source. Since the load is a motor or a fan, most working conditions require DC power to always provide power to the fan or the motor. The DC source of each CHB needs to always provide energy to the load, which is different from the case where the DC source of the CHB is a battery, because the battery has both charging and discharging working conditions.

[0053] A specific implementation of a VSR circuit is described below with reference to the accompanying drawings.

[0054] See also Figure 5 , which is a schematic diagram of a VSR circuit provided in an embodiment of the present application.

[0055] In the power converter provided in the embodiment of the present application, the rectifier circuit is taken as a VSR, and the VSR is introduced as a three-level active clamp rectifier, that is, the rectifier circuit includes a three-phase three-level active clamp bridge arm;

[0056] The input end of the three-phase active midpoint clamped three-level bridge arm is connected to the corresponding secondary winding through an inductor, that is, the U phase is connected to the U phase secondary winding through the inductor LA. The V phase is connected to the V phase secondary winding through the inductor LB. The W phase is connected to the W phase secondary winding through the inductor LC.

[0057] The output end of the three-phase active midpoint clamped three-level bridge arm is connected to the input end of the corresponding H-bridge inverter circuit.

[0058] like Figure 5 As shown, the U-phase bridge arm includes six switching tubes, and the bridge arm includes four switching tubes connected in series, namely Q1A, Q5A, Q6A and Q4A. The midpoint clamped switching tube of the U-phase bridge arm includes Q2A and Q3A. The V-phase bridge arm includes six switching tubes, and the bridge arm includes four switching tubes connected in series, namely Q1B, Q5B, Q6B and Q4B. The midpoint clamped switching tube of the U-phase bridge arm includes Q2B and Q3C. The W-phase bridge arm includes six switching tubes, and the bridge arm includes four switching tubes connected in series, namely Q1C, Q5C, Q6C and Q4C. The midpoint clamped switching tube of the U-phase bridge arm includes Q2C and Q3C.

[0059] The DC bus capacitors include C1 and C2 connected in series, and two ends of the two DC bus capacitors connected in series serve as two output ends of the rectifier circuit, namely Vdc+ and Vdc-.

[0060] The above introduces the implementation method of the VSR circuit. The following introduces two implementation methods of the CHB circuit.

[0061] See also Figure 6 , which is a schematic diagram of a CHB circuit provided in an embodiment of the present application.

[0062] The power converter provided in the embodiment of the present application, the H-bridge inverter circuit, namely, CHB includes two bridge arms connected in parallel, each bridge arm includes two switch tubes connected in series, namely, the H-bridge inverter circuit is implemented by using a typical full-bridge inverter circuit; the midpoint of the two bridge arms serves as the output end of the H-bridge inverter circuit. Figure 6 As shown, the H-bridge inverter circuit includes four switch tubes Q1-Q4, wherein Q1 and Q2 are connected in series to form one bridge arm, and Q3 and Q4 are connected in series to form another bridge arm. Capacitor C11 serves as a DC bus capacitor. The two ends of capacitor C11 serve as the positive input terminal and the negative input terminal of CHB respectively. The midpoints of the two bridge arms of the H-bridge are L1 and L2 respectively, which serve as the two output terminals of the CHB circuit.

[0063] Figure 6 The H-bridge inverter circuit shown is a typical inverter circuit, which is used to invert the direct current at the input end into an alternating current output.

[0064] See also Figure 7 , which is a schematic diagram of another CHB circuit provided in an embodiment of the present application.

[0065] In the power converter provided in the embodiment of the present application, the H-bridge inverter circuit includes two parallel-connected passive mid-point clamped three-level bridge arms or active mid-point clamped three-level bridge arms.

[0066] Figure 7 The DC bus capacitor includes a first capacitor C11 and a second capacitor C12 connected in series. It should be understood that the two ends of C11 and C12 connected in series serve as the positive input terminal and the negative input terminal of CHB respectively, and are connected to the output terminal of the corresponding DAB.

[0067] Figure 7 The three-level bridge arm in the embodiment includes two parallel connections, wherein the first bridge arm includes four switch tubes Q1-Q4 connected in series, and the second bridge arm includes four switch tubes Q5-Q8 connected in series. Figure 7The H-bridge inverter circuit shown includes two parallel passive midpoint clamped three-level bridge arms, that is, the midpoint clamped is an uncontrolled device diode, and the midpoint clamped diode corresponding to the first bridge arm includes a first diode D1 and a second diode D2, the cathode of D1 is connected to the first end of Q2, the second end of Q1 is connected to the first end of Q2, and the first end of Q1 is connected to the first end of C11. The anode of D1 is connected to the second end of C11, the cathode of D2 is connected to the anode of D1, the anode of D2 is connected to the second end of Q3, and the first end of Q3 is connected to the second end of Q2. Similarly, the cathode of D3 is connected to the first end of Q6, the second end of Q5 is connected to the first end of Q6, the first end of Q5 is connected to the first end of C11, the anode of D3 is connected to the second end of C11, the cathode of D4 is connected to the anode of D3, the cathode of D4 is connected to the second end of Q7, and the first end of Q7 is connected to the second end of Q6.

[0068] The midpoint of the first bridge arm, namely the second end of Q2, serves as the first output end L1 of CHB, and the midpoint of the second bridge arm, namely the second end of Q6, serves as the second output end L2 of CHB.

[0069] It should be understood that the H-bridge inverter circuit may also include an active midpoint clamped three-level bridge arm, that is, Figure 7 D1-D4 in the circuit can be replaced with controllable switch tubes, such as IGBT.

[0070] contrast Figure 6 and Figure 7 It can be seen that Figure 6 The CHB uses fewer switch tubes. Figure 7 The CHB uses a large number of switch tubes. When the voltage of a single CHB is the same, Figure 7 The topology can reduce the voltage that a single switch tube bears. Figure 6 The voltage borne by a single switch tube in the CHB topology shown is relatively high. The embodiment of the present application does not specifically limit the internal topology of the CHB, and it can be selected according to actual needs.

[0071] Based on the AC power supply converter provided in the above embodiment, the embodiment of the present application also provides a motor, which is described in detail below with reference to the accompanying drawings.

[0072] See also Figure 8 , which is a schematic diagram of a motor provided in an embodiment of the present application.

[0073] The motor provided in the embodiment of the present application includes a three-phase winding 802 and the AC power supply converter 801 introduced in the above embodiment, and the AC power supply converter 801 is used to supply power to the three-phase winding 802 .

[0074] The motor provided in the embodiment of the present application includes the AC power supply power converter introduced above, because the AC power supply power converter can convert several thousand volts of high-voltage AC into ordinary multi-channel lower AC voltage. The AC voltage is rectified and converted into independent DC sources, which provide DC voltage support to the cascaded full-bridge inverter circuit respectively. The cascaded full-bridge inverter circuit inverts to form a high-voltage AC with variable frequency, which can provide energy for the high-voltage motor. Therefore, it can solve the problem of high voltage resistance of semiconductor devices in the current power supply of high-voltage motors. This technical solution can use ordinary switching tubes to reduce costs.

[0075] Based on an AC power supply power converter provided in the above embodiment, the embodiment of the present application further provides a fan for a pneumatic pipe network, which is described in detail below in conjunction with the accompanying drawings.

[0076] See also Fig. 9 , which is a schematic diagram of a fan of a pneumatic pipe network provided in an embodiment of the present application.

[0077] The fan of the pneumatic pipe network provided in the embodiment of the present application includes a three-phase winding 802 and a DC power supply converter 801 introduced in the above embodiment, and the DC power supply converter 801 is used to supply power to the three-phase winding 802 .

[0078] The fan of the pneumatic pipe network provided in the embodiment of the present application includes the AC power supply power converter introduced above. Since the AC power supply power converter can convert several thousand volts of high-voltage AC into ordinary multiple-channel lower DC voltage. The DC voltages are independent of each other and provide DC voltage support to the cascaded full-bridge inverter circuit respectively; the cascaded full-bridge inverter circuit inverts to form a high-frequency variable-voltage AC, which can provide energy for the fan of the pneumatic pipe network. Therefore, it can solve the problem of high voltage resistance of semiconductor devices in the power supply of the fan of the current high-voltage pneumatic pipe network. The technical solution can use ordinary switch tubes to reduce costs.

[0079] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. For the method disclosed in the embodiment, since it corresponds to the product embodiment disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the product embodiment part.

[0080] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be 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 the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An AC powered power converter, It is characterized in that include: A transformer, 3n rectifier circuits and a three-phase cascade H-bridge circuit; the transformer includes a primary winding and 3n secondary windings; The 3n secondary windings correspond to the 3n rectifier circuits one by one; The primary winding is used to connect to alternating current, and the input ends of the 3n rectifier circuits are used to connect to the corresponding secondary windings; Each phase cascade H-bridge circuit includes n H-bridge inverter circuits, where n is an integer greater than or equal to 2; the rectifier circuit and the inverter circuit correspond one to one, and the input end of each H-bridge inverter circuit is connected to the output end of the corresponding rectifier circuit; the output ends of the n H-bridge inverter circuits are connected in series, and each phase cascade H-bridge circuit is used to power one phase of a three-phase load.

2. The power converter according to claim 1, It is characterized in that There is one transformer, and the transformer includes a primary winding and 3n secondary windings.

3. The power converter according to claim 1, It is characterized in that There are 3n transformers, each of which includes a primary winding and a secondary winding; the primary winding of each transformer is connected in parallel to connect the alternating current, and the secondary winding of each transformer is connected to a corresponding rectifier circuit.

4. The power converter according to any one of claims 1 to 3, It is characterized in that The rectifier circuit is a voltage type rectifier.

5. The power converter according to claim 4, It is characterized in that The rectifier circuit comprises a three-phase active midpoint clamped three-level bridge arm; The input end of the three-phase active midpoint clamped three-level bridge arm is connected to the corresponding secondary winding through an inductor, and the output end of the three-phase active midpoint clamped three-level bridge arm is connected to the input end of the corresponding H-bridge inverter circuit.

6. The power converter according to any one of claims 1 to 3, It is characterized in that The H-bridge inverter circuit includes two bridge arms connected in parallel, and each bridge arm includes two switch tubes connected in series; the midpoint of the two bridge arms serves as the output end of the H-bridge inverter circuit.

7. The power converter according to any one of claims 1 to 3, It is characterized in that The H-bridge inverter circuit comprises two parallel-connected passive mid-point clamped three-level bridge arms or active mid-point clamped three-level bridge arms.

8. The power converter according to claim 2, It is characterized in that The transformer is a multi-split winding transformer, and the voltage of the alternating current connected to the input end of the transformer is greater than or equal to 10 kV.

9. A motor, It is characterized in that It comprises a three-phase winding and an AC-powered power converter as claimed in any one of claims 1 to 8, wherein the AC-powered power converter is used to supply power to the three-phase winding.

10. A fan for a pneumatic pipe network, It is characterized in that It comprises a three-phase winding and an AC-powered power converter as claimed in any one of claims 1 to 8, wherein the AC-powered power converter is used to supply power to the three-phase winding.

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