Three-phase hybrid clamping type three-level inverter with wide voltage output range

Abstract

The invention discloses a three-phase hybrid clamping type three-level inverter with a wide voltage output range, relates to the field of inverters, and particularly relates to a three-phase voltage source inverter. The three-phase voltage source inverter comprises a direct-current voltage source module, a Y-type inversion module, a hybrid clamping module, an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) control module and a three-phase load module. The DC power supply module is used as a DC side power supply of the inverter, the Y-type inversion module under the control of the MOSFET control module can realize inversion output in a wide voltage output range, and through the clamping effect of the hybrid clamping module of the switch bridge part, the whole circuit obtains a higher voltage withstanding level, and the output waveform obtains higher waveform quality. The circuit has the characteristics of wide voltage output range, higher switching frequency, higher withstand voltage level and higher waveform quality, and is very wide in application prospect.

Description

Technical Field

[0001] This patent relates to the field of multi-level inverter technology, and specifically to a three-phase hybrid clamped three-level inverter with a wide voltage output range. Background Art

[0002] With the widespread application of new energy, power electronics technology has also flourished, and inverters are a key research object of power electronics. An inverter is a device that converts direct current into alternating current based on power electronic switching devices. Currently, the more commonly used three-phase inverter types are: voltage source inverter (VSI), current source inverter (CSI), PWM inverter, etc. In inverter applications, due to the particularly high requirements for motor drive provided by fuel cells, the inverter must cope with the wide DC voltage variation of the fuel cell that powers the motor drive, and should also output high-quality motor voltage. Traditional three-phase full-bridge inverters have problems with poor output waveform quality and low switching frequency, while traditional clamped inverters have problems with overvoltage of the inner device of the bridge arm, unbalanced blocking voltage of the power switch, and difficulty in rapid recovery of the reverse voltage of the clamping diode.

[0003] To solve the above problems, this patent proposes a three-phase hybrid clamped three-level inverter with a wide voltage output range. Summary of the invention

[0004] The purpose of this patent is to propose a three-phase hybrid clamped three-level inverter with a wide voltage output range to solve the problem that traditional inverters cannot achieve high waveform quality and a wide voltage output range.

[0005] The technical solution adopted by this patent is: a three-phase hybrid clamped three-level inverter with a wide voltage output range, including a DC voltage source module, a Y-type inverter module, a hybrid clamping module, a MOSFET control module, and a three-phase load module; it is characterized in that the output of the DC voltage source module is connected to the input of the Y-type inverter module, the hybrid clamping module is connected to the Y-type inverter module, the output of the MOSFET control module is connected to the input of the Y-type inverter module, and the output of the Y-type inverter module is connected to the input of the three-phase load module; the DC voltage source module includes a voltage source Vdc1, a voltage source Vdc2, a capacitor C i, ground port GND1; the Y-type inverter module includes a crystal switch tube T1, a crystal switch tube T2, a crystal switch tube T3, a crystal switch tube T4, a crystal switch tube T5, a crystal switch tube T6, a crystal switch tube T7, a crystal switch tube T8, a crystal switch tube T9, a crystal switch tube T10, a crystal switch tube T11, a crystal switch tube T12, a crystal switch tube T13, a crystal switch tube T14, a crystal switch tube T15, a crystal switch tube T16, a crystal switch tube T17, a crystal switch tube T18, a crystal switch tube T19, a crystal switch tube T20, a crystal switch tube T21, a crystal switch tube T22, a crystal switch tube T23, a crystal switch tube T24, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a diode D7, a diode D8, a diode D9, a diode D10, a diode D11, a diode D 12, diode D13, diode D14, diode D15, diode D16, diode D17, diode D18, diode D19, diode D20, diode D21, diode D22, diode D23, diode D24, inductor L1, inductor L2, inductor L3, capacitor C9, capacitor C10, capacitor C11; the hybrid clamping module includes diode D25, diode D26, diode D27, diode D28, diode D29, diode D30, diode D31, diode D32, diode D33, diode D34, diode D35, diode D36, inductor L9, capacitor C1, capacitor C2, capacitor C3, capacitor C4, capacitor C5, capacitor C6, capacitor C7, capacitor C8; the three-phase load module includes resistor R1, resistor R2, resistor R3, inductor L4, inductor L5, inductor L6.

[0006] In the DC voltage source module, the voltage source Vdc1 and the voltage source Vdc2 are two identical DC voltage sources, the amplitude of which is Vdc / 2, and the positive electrode of the voltage source Vdc1 is connected to the capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the drain of transistor switch tube T1, the negative electrode is connected to the positive electrode of voltage source Vdc2 and ground port GND1, and the negative electrode of voltage source Vdc2 is connected to capacitor C i The cathode is connected to the cathode of capacitor C2 and the source of transistor switch tube T4.

[0007] The MOSFET control module outputs 24 control signals, and the output interfaces are MOS tube T1, MOS tube T2, MOS tube T3, MOS tube T4, MOS tube T5, MOS tube T6, MOS tube T7, MOS tube T8, MOS tube T9, MOS tube T10, MOS tube T11, MOS tube T12, MOS tube T13, MOS tube T14, MOS tube T15, MOS tube T16, MOS tube T17, MOS tube T18, MOS tube T19, MOS tube T20, MOS tube T21, MOS tube T22, MOS tube T23, and MOS tube T24.

[0008] In the Y-type inverter module, the gate of the transistor switch tube T1 is connected to the T1 output interface of the MOSFET control module, and the drain is connected to the capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the cathode of diode D1, the source electrode is connected to the drain of crystal switch tube T2, the anode of diode D1 and the positive electrode of capacitor C3, the gate of crystal switch tube T2 is connected to the T2 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T1, the cathode of diode D2 and the positive electrode of capacitor C3, the source electrode is connected to the drain of crystal switch tube T3, the anode of diode D2 and the positive electrode of inductor L1, the gate of crystal switch tube T3 is connected to the T3 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T2, the cathode of diode D3 and the positive electrode of inductor L1, the source electrode is connected to the drain of crystal switch tube T4, the anode of diode D3 and the negative electrode of capacitor C3, the gate of crystal switch tube T4 is connected to the T4 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T3, the anode of diode D3 and the negative electrode of capacitor C3, the source electrode is connected to the capacitor C i The cathode is connected to the cathode of capacitor C2 and the anode of diode D4, the gate of transistor switch tube T5 is connected to the T5 output interface of MOSFET control module, and the drain is connected to capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the cathode of diode D5, the source electrode is connected to the drain of crystal switch tube T6, the anode of diode D5 and the positive electrode of capacitor C4, the gate of crystal switch tube T6 is connected to the T6 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T5, the cathode of diode D6 and the positive electrode of capacitor C4, the source electrode is connected to the drain of crystal switch tube T7, the anode of diode D6 and the positive electrode of inductor L5, the gate of crystal switch tube T7 is connected to the T7 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T6, the cathode of diode D7 and the positive electrode of inductor L2, the source electrode is connected to the drain of crystal switch tube T8, the anode of diode D7 and the negative electrode of capacitor C4, the gate of crystal switch tube T8 is connected to the T8 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T7, the anode of diode D8 and the negative electrode of capacitor C4, the source electrode is connected to the capacitor C iThe cathode is connected to the cathode of capacitor C2 and the anode of diode D8, the gate of transistor switch tube T9 is connected to the output interface of MOSFET control module T9, and the drain is connected to capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the cathode of diode D9, the source electrode is connected to the drain of crystal switch tube T10, the anode of diode D9 and the positive electrode of capacitor C5, the gate of crystal switch tube T10 is connected to the T10 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T9, the cathode of diode D10 and the positive electrode of capacitor C5, the source electrode is connected to the drain of crystal switch tube T11, the anode of diode D10 and the positive electrode of inductor L3, the gate of crystal switch tube T11 is connected to the T11 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T10, the cathode of diode D11 and the positive electrode of inductor L3, the source electrode is connected to the drain of crystal switch tube T12, the anode of diode D11 and the negative electrode of capacitor C5, the gate of crystal switch tube T12 is connected to the T12 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T11, the anode of diode D12 and the negative electrode of capacitor C5, the source electrode is connected to the capacitor C i The negative electrode is connected to the negative electrode of capacitor C2 and the anode of diode D12, the gate of crystal switch tube T13 is connected to the T13 output interface of MOSFET control module, the drain is connected to the cathode of diode D13 and the positive electrode of capacitor C9 and the positive electrode of resistor R1, the source is connected to the drain of crystal switch tube T14 and the anode of diode D13 and the positive electrode of capacitor C6, the gate of crystal switch tube T14 is connected to the T14 output interface of MOSFET control module, the drain is connected to the source of crystal switch tube T13 and the cathode of diode D14 and the positive electrode of capacitor C6, the source is connected to the drain of crystal switch tube T15 and diode D The anode of the transistor T14 is connected to the negative electrode of the inductor L1, the gate of the transistor T15 is connected to the output interface of the MOSFET control module T15, the drain is connected to the source of the transistor T14, the cathode of the diode D15 and the negative electrode of the inductor L1, the source is connected to the drain of the transistor T16, the anode of the diode D15 and the negative electrode of the capacitor C6, the gate of the transistor T16 is connected to the output interface of the MOSFET control module T16, the drain is connected to the source of the transistor T15, the cathode of the diode D16 and the negative electrode of the capacitor C6, the source is connected to the anode of the diode D16 and the negative electrode of the capacitor C2 and the capacitor C iThe negative electrode is connected, the gate of the crystal switch tube T17 is connected to the T17 output interface of the MOSFET control module, the drain is connected to the cathode of the diode D17, the positive electrode of the capacitor C10 and the positive electrode of the resistor R2, the source is connected to the drain of the crystal switch tube T18, the anode of the diode D17 and the positive electrode of the capacitor C7, the gate of the crystal switch tube T18 is connected to the T18 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T17, the cathode of the diode D18 and the positive electrode of the capacitor C7, the source is connected to the drain of the crystal switch tube T19, the anode of the diode D18 and the inductor L 2, the gate of the crystal switch tube T19 is connected to the T19 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T18, the cathode of the diode D19 and the negative electrode of the inductor L2, the source is connected to the drain of the crystal switch tube T20, the anode of the diode D19 and the negative electrode of the capacitor C7, the gate of the crystal switch tube T20 is connected to the T20 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T19, the cathode of the diode D20 and the negative electrode of the capacitor C7, the source is connected to the anode of the diode D20, the negative electrode of the capacitor C2 and the capacitor C i The negative electrode is connected, the gate of the crystal switch tube T21 is connected to the T21 output interface of the MOSFET control module, the drain is connected to the cathode of the diode D21, the positive electrode of the capacitor C11 and the positive electrode of the resistor R3, the source is connected to the drain of the crystal switch tube T22, the anode of the diode D21 and the positive electrode of the capacitor C8, the gate of the crystal switch tube T22 is connected to the T22 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T21, the cathode of the diode D22 and the positive electrode of the capacitor C8, the source is connected to the drain of the crystal switch tube T23, the anode of the diode D22 and the inductor L 3, the gate of the crystal switch tube T23 is connected to the T23 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T22, the cathode of the diode D23 and the negative electrode of the inductor L3, the source is connected to the drain of the crystal switch tube T24, the anode of the diode D23 and the negative electrode of the capacitor C8, the gate of the crystal switch tube T24 is connected to the T24 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T23, the cathode of the diode D24 and the negative electrode of the capacitor C8, the source is connected to the anode of the diode D24, the negative electrode of the capacitor C2 and the capacitor C i Negative pole connected.

[0009] In the hybrid clamping module, the cathode of the diode D25 is connected to the positive electrode of the capacitor C3, and the anode is connected to the cathode of the diode D26, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2. The cathode of the diode D26 is connected to the anode of the diode D25, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2, and the anode is connected to the negative electrode of the capacitor C3. The cathode of the diode D27 is connected to the positive electrode of the capacitor C4, and the anode is connected to the cathode of the diode D28, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2. The cathode of the diode D28 is connected to the anode of the diode D27, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2, and the anode is connected to the negative electrode of the capacitor C4. The cathode of the diode D29 is connected to the positive electrode of the capacitor C5, and the anode is connected to the cathode of the diode D30, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2, and the anode is connected to the negative electrode of the capacitor C5. , the cathode of diode D31 is connected to the positive electrode of capacitor C6, and the anode is connected to the cathode of diode D32, the negative electrode of capacitor C1 and the positive electrode of capacitor C2. The cathode of diode D32 is connected to the anode of diode D31, the negative electrode of capacitor C1 and the positive electrode of capacitor C2, and the anode is connected to the negative electrode of capacitor C6. The cathode of diode D33 is connected to the positive electrode of capacitor C7, and the anode is connected to the cathode of diode D34, the negative electrode of capacitor C1 and the positive electrode of capacitor C2. The cathode of diode D34 is connected to the anode of diode D33, the negative electrode of capacitor C1 and the positive electrode of capacitor C2, and the anode is connected to the negative electrode of capacitor C7. The cathode of diode D35 is connected to the positive electrode of capacitor C8, and the anode is connected to the cathode of diode D36, the negative electrode of capacitor C1 and the positive electrode of capacitor C2. The cathode of diode D36 is connected to the anode of diode D35, the negative electrode of capacitor C1 and the positive electrode of capacitor C2, and the anode is connected to the negative electrode of capacitor C8. The positive electrode of capacitor C1 is connected to capacitor C i The positive electrode is connected to the negative electrode of capacitor C2 and the capacitor C i Negative pole connected.

[0010] In the three-phase load module, the positive electrode of resistor R1 is connected to the positive electrode of capacitor C9, and the negative electrode is connected to the positive electrode of inductor L4, the positive electrode of resistor R2 is connected to the positive electrode of capacitor C10, and the negative electrode is connected to the positive electrode of inductor L5, the positive electrode of resistor R3 is connected to the positive electrode of capacitor C11, and the negative electrode is connected to the positive electrode of inductor L6, and the negative electrode of inductor L4, the negative electrode of inductor L5, and the negative electrode of inductor L6 adopt a star-shaped connection method with an ungrounded neutral point.

[0011] The advantages of the three-phase hybrid clamped three-level inverter with a wide voltage output range in this patent are: first, in the inverter bridge part, a different connection method from the traditional inverter is used to connect three identical DC / DC converters to a common "Y" point; second, a hybrid clamping module is added to the inverter bridge switch part, so that the inverter described in this patent can achieve AC voltage output with a wide voltage output range and high waveform quality. Compared with the traditional three-phase voltage-type bridge inverter circuit, the three-phase hybrid clamped three-level inverter with a wide voltage output range in this patent has a wider range of voltage output, higher switching frequency, higher voltage resistance level, and higher waveform quality.

[0012] In order to more clearly illustrate the three-phase hybrid clamped three-level inverter with a wide voltage output range proposed in this patent, the patent is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the three-phase hybrid clamped three-level inverter with a wide voltage output range proposed in this patent, the patent is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0014] Figure 1 This is a circuit structure diagram of a three-phase hybrid clamped three-level inverter with a wide voltage output range in this patent.

[0015] Figure 2 It is the buck-boost module of phase A in the inverter.

[0016] Figure 3 It is the buck working mode when the output voltage is lower than the input voltage.

[0017] Figure 4 It is the boost working mode when the output voltage is higher than the input voltage.

[0018] Figure 5 It is the clamp capacitor charging circuit when the inverter outputs Vdc / 2 in operating mode 1.

[0019] Figure 6 It is the clamping capacitor discharge circuit when the inverter outputs Vdc / 2 in operating mode 1.

[0020] Figure 7 It is the clamping capacitor charging circuit when the inverter outputs zero voltage in working mode 2.

[0021] Figure 8 It is the clamping capacitor discharge circuit when the inverter outputs zero voltage in working mode 2.

[0022] Fig. 9It is the clamping capacitor charging circuit when the inverter outputs zero voltage in working mode 3.

[0023] Fig.10 This is the clamp capacitor charging circuit when the inverter outputs -Vdc / 2 in operating mode 4. DETAILED DESCRIPTION

[0024] The following will combine the drawings in the embodiments of this patent to clearly and completely describe the technical solutions in the embodiments of this patent. It should be noted that the embodiments described here are only partial embodiments of this patent, not all implementation methods of this patent, and the embodiments are only exemplary.

[0025] Figure 1 The circuit structure diagram of a three-phase hybrid clamped three-level inverter with a wide voltage output range of the present invention is as follows: it includes a DC voltage source module, a Y-type inverter module, a hybrid clamping module, a MOSFET control module, and a three-phase load module; it is characterized in that the output of the DC voltage source module is connected to the input of the Y-type inverter module, the hybrid clamping module is connected to the Y-type inverter module, the output of the MOSFET control module is connected to the input of the Y-type inverter module, and the output of the Y-type inverter module is connected to the input of the three-phase load module; the DC voltage source module includes a voltage source Vdc1, a voltage source Vdc2, a capacitor C i, ground port GND1; the Y-type inverter module includes a crystal switch tube T1, a crystal switch tube T2, a crystal switch tube T3, a crystal switch tube T4, a crystal switch tube T5, a crystal switch tube T6, a crystal switch tube T7, a crystal switch tube T8, a crystal switch tube T9, a crystal switch tube T10, a crystal switch tube T11, a crystal switch tube T12, a crystal switch tube T13, a crystal switch tube T14, a crystal switch tube T15, a crystal switch tube T16, a crystal switch tube T17, a crystal switch tube T18, a crystal switch tube T19, a crystal switch tube T20, a crystal switch tube T21, a crystal switch tube T22, a crystal switch tube T23, a crystal switch tube T24, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a diode D7, a diode D8, a diode D9, a diode D10, a diode D11, a diode D 12, diode D13, diode D14, diode D15, diode D16, diode D17, diode D18, diode D19, diode D20, diode D21, diode D22, diode D23, diode D24, inductor L1, inductor L2, inductor L3, capacitor C9, capacitor C10, capacitor C11; the hybrid clamping module includes diode D25, diode D26, diode D27, diode D28, diode D29, diode D30, diode D31, diode D32, diode D33, diode D34, diode D35, diode D36, inductor L9, capacitor C1, capacitor C2, capacitor C3, capacitor C4, capacitor C5, capacitor C6, capacitor C7, capacitor C8; the three-phase load module includes resistor R1, resistor R2, resistor R3, inductor L4, inductor L5, inductor L6.

[0026] In the DC voltage source module, the voltage source Vdc1 and the voltage source Vdc2 are two identical DC voltage sources, the amplitude of which is Vdc / 2, and the positive electrode of the voltage source Vdc1 is connected to the capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the drain of transistor switch tube T1, the negative electrode is connected to the positive electrode of voltage source Vdc2 and ground port GND1, and the negative electrode of voltage source Vdc2 is connected to capacitor C i The cathode is connected to the cathode of capacitor C2 and the source of transistor switch tube T4.

[0027] The MOSFET control module outputs 24 control signals, and the output interfaces are MOS tube T1, MOS tube T2, MOS tube T3, MOS tube T4, MOS tube T5, MOS tube T6, MOS tube T7, MOS tube T8, MOS tube T9, MOS tube T10, MOS tube T11, MOS tube T12, MOS tube T13, MOS tube T14, MOS tube T15, MOS tube T16, MOS tube T17, MOS tube T18, MOS tube T19, MOS tube T20, MOS tube T21, MOS tube T22, MOS tube T23, and MOS tube T24.

[0028] In the Y-type inverter module, the gate of the transistor switch tube T1 is connected to the T1 output interface of the MOSFET control module, and the drain is connected to the capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the cathode of diode D1, the source electrode is connected to the drain of crystal switch tube T2, the anode of diode D1 and the positive electrode of capacitor C3, the gate of crystal switch tube T2 is connected to the T2 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T1, the cathode of diode D2 and the positive electrode of capacitor C3, the source electrode is connected to the drain of crystal switch tube T3, the anode of diode D2 and the positive electrode of inductor L1, the gate of crystal switch tube T3 is connected to the T3 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T2, the cathode of diode D3 and the positive electrode of inductor L1, the source electrode is connected to the drain of crystal switch tube T4, the anode of diode D3 and the negative electrode of capacitor C3, the gate of crystal switch tube T4 is connected to the T4 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T3, the anode of diode D3 and the negative electrode of capacitor C3, the source electrode is connected to the capacitor C i The cathode is connected to the cathode of capacitor C2 and the anode of diode D4, the gate of transistor switch tube T5 is connected to the T5 output interface of MOSFET control module, and the drain is connected to capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the cathode of diode D5, the source electrode is connected to the drain of crystal switch tube T6, the anode of diode D5 and the positive electrode of capacitor C4, the gate of crystal switch tube T6 is connected to the T6 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T5, the cathode of diode D6 and the positive electrode of capacitor C4, the source electrode is connected to the drain of crystal switch tube T7, the anode of diode D6 and the positive electrode of inductor L5, the gate of crystal switch tube T7 is connected to the T7 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T6, the cathode of diode D7 and the positive electrode of inductor L2, the source electrode is connected to the drain of crystal switch tube T8, the anode of diode D7 and the negative electrode of capacitor C4, the gate of crystal switch tube T8 is connected to the T8 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T7, the anode of diode D8 and the negative electrode of capacitor C4, the source electrode is connected to the capacitor C iThe cathode is connected to the cathode of capacitor C2 and the anode of diode D8, the gate of transistor switch tube T9 is connected to the output interface of MOSFET control module T9, and the drain is connected to capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the cathode of diode D9, the source electrode is connected to the drain of crystal switch tube T10, the anode of diode D9 and the positive electrode of capacitor C5, the gate of crystal switch tube T10 is connected to the T10 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T9, the cathode of diode D10 and the positive electrode of capacitor C5, the source electrode is connected to the drain of crystal switch tube T11, the anode of diode D10 and the positive electrode of inductor L3, the gate of crystal switch tube T11 is connected to the T11 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T10, the cathode of diode D11 and the positive electrode of inductor L3, the source electrode is connected to the drain of crystal switch tube T12, the anode of diode D11 and the negative electrode of capacitor C5, the gate of crystal switch tube T12 is connected to the T12 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T11, the anode of diode D12 and the negative electrode of capacitor C5, the source electrode is connected to the capacitor C i The negative electrode is connected to the negative electrode of capacitor C2 and the anode of diode D12, the gate of crystal switch tube T13 is connected to the T13 output interface of MOSFET control module, the drain is connected to the cathode of diode D13 and the positive electrode of capacitor C9 and the positive electrode of resistor R1, the source is connected to the drain of crystal switch tube T14 and the anode of diode D13 and the positive electrode of capacitor C6, the gate of crystal switch tube T14 is connected to the T14 output interface of MOSFET control module, the drain is connected to the source of crystal switch tube T13 and the cathode of diode D14 and the positive electrode of capacitor C6, the source is connected to the drain of crystal switch tube T15 and diode D The anode of the transistor T14 is connected to the negative electrode of the inductor L1, the gate of the transistor T15 is connected to the output interface of the MOSFET control module T15, the drain is connected to the source of the transistor T14, the cathode of the diode D15 and the negative electrode of the inductor L1, the source is connected to the drain of the transistor T16, the anode of the diode D15 and the negative electrode of the capacitor C6, the gate of the transistor T16 is connected to the output interface of the MOSFET control module T16, the drain is connected to the source of the transistor T15, the cathode of the diode D16 and the negative electrode of the capacitor C6, the source is connected to the anode of the diode D16 and the negative electrode of the capacitor C2 and the capacitor C iThe negative electrode is connected, the gate of the crystal switch tube T17 is connected to the T17 output interface of the MOSFET control module, the drain is connected to the cathode of the diode D17, the positive electrode of the capacitor C10 and the positive electrode of the resistor R2, the source is connected to the drain of the crystal switch tube T18, the anode of the diode D17 and the positive electrode of the capacitor C7, the gate of the crystal switch tube T18 is connected to the T18 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T17, the cathode of the diode D18 and the positive electrode of the capacitor C7, the source is connected to the drain of the crystal switch tube T19, the anode of the diode D18 and the inductor L 2, the gate of the crystal switch tube T19 is connected to the T19 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T18, the cathode of the diode D19 and the negative electrode of the inductor L2, the source is connected to the drain of the crystal switch tube T20, the anode of the diode D19 and the negative electrode of the capacitor C7, the gate of the crystal switch tube T20 is connected to the T20 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T19, the cathode of the diode D20 and the negative electrode of the capacitor C7, the source is connected to the anode of the diode D20, the negative electrode of the capacitor C2 and the capacitor C i The negative electrode is connected, the gate of the crystal switch tube T21 is connected to the T21 output interface of the MOSFET control module, the drain is connected to the cathode of the diode D21, the positive electrode of the capacitor C11 and the positive electrode of the resistor R3, the source is connected to the drain of the crystal switch tube T22, the anode of the diode D21 and the positive electrode of the capacitor C8, the gate of the crystal switch tube T22 is connected to the T22 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T21, the cathode of the diode D22 and the positive electrode of the capacitor C8, the source is connected to the drain of the crystal switch tube T23, the anode of the diode D22 and the inductor L 3, the gate of the crystal switch tube T23 is connected to the T23 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T22, the cathode of the diode D23 and the negative electrode of the inductor L3, the source is connected to the drain of the crystal switch tube T24, the anode of the diode D23 and the negative electrode of the capacitor C8, the gate of the crystal switch tube T24 is connected to the T24 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T23, the cathode of the diode D24 and the negative electrode of the capacitor C8, the source is connected to the anode of the diode D24, the negative electrode of the capacitor C2 and the capacitor C i Negative pole connected.

[0029] In the hybrid clamping module, the cathode of the diode D25 is connected to the positive electrode of the capacitor C3, and the anode is connected to the cathode of the diode D26, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2. The cathode of the diode D26 is connected to the anode of the diode D25, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2, and the anode is connected to the negative electrode of the capacitor C3. The cathode of the diode D27 is connected to the positive electrode of the capacitor C4, and the anode is connected to the cathode of the diode D28, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2. The cathode of the diode D28 is connected to the anode of the diode D27, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2, and the anode is connected to the negative electrode of the capacitor C4. The cathode of the diode D29 is connected to the positive electrode of the capacitor C5, and the anode is connected to the cathode of the diode D30, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2, and the anode is connected to the negative electrode of the capacitor C5. , the cathode of diode D31 is connected to the positive electrode of capacitor C6, and the anode is connected to the cathode of diode D32, the negative electrode of capacitor C1 and the positive electrode of capacitor C2. The cathode of diode D32 is connected to the anode of diode D31, the negative electrode of capacitor C1 and the positive electrode of capacitor C2, and the anode is connected to the negative electrode of capacitor C6. The cathode of diode D33 is connected to the positive electrode of capacitor C7, and the anode is connected to the cathode of diode D34, the negative electrode of capacitor C1 and the positive electrode of capacitor C2. The cathode of diode D34 is connected to the anode of diode D33, the negative electrode of capacitor C1 and the positive electrode of capacitor C2, and the anode is connected to the negative electrode of capacitor C7. The cathode of diode D35 is connected to the positive electrode of capacitor C8, and the anode is connected to the cathode of diode D36, the negative electrode of capacitor C1 and the positive electrode of capacitor C2. The cathode of diode D36 is connected to the anode of diode D35, the negative electrode of capacitor C1 and the positive electrode of capacitor C2, and the anode is connected to the negative electrode of capacitor C8. The positive electrode of capacitor C1 is connected to capacitor C i The positive electrode is connected to the negative electrode of capacitor C2 and the capacitor C i Negative pole connected.

[0030] In the three-phase load module, the positive electrode of resistor R1 is connected to the positive electrode of capacitor C9, and the negative electrode is connected to the positive electrode of inductor L4, the positive electrode of resistor R2 is connected to the positive electrode of capacitor C10, and the negative electrode is connected to the positive electrode of inductor L5, the positive electrode of resistor R3 is connected to the positive electrode of capacitor C11, and the negative electrode is connected to the positive electrode of inductor L6, and the negative electrode of inductor L4, the negative electrode of inductor L5, and the negative electrode of inductor L6 adopt a star-shaped connection method with an ungrounded neutral point.

[0031] Next, please refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 The difference between the Y-type inverter bridge structure used in this patent and the traditional IGBT three-phase fully controlled bridge voltage source inverter is that this patent adds 18 groups of MOSFET transistors and 24 groups of corresponding freewheeling diodes to the inverter bridge, achieving a wide voltage output range while achieving three-phase three-level output. The Y-type inverter bridge part is composed of three buck-boost modules. Figure 2 For the buck-boost module of phase a, the control strategies of the six modules are independent of each other, which means that the control strategy of the three phases is relatively simple. Taking the voltage of phase a as an example, the transistors T13 and T14 are kept on continuously, the transistors T15 and T16 are kept off continuously, and the transistors T1, T2, T3, and T4 are turned on alternately to obtain Figure 3 At this time, the a-phase buck-boost module is in buck mode, and the output voltage is lower than the input voltage; transistors T1 and T2 are kept turned on continuously, transistors T3 and T4 are kept turned off continuously, and transistors T13, T14, T15, and T16 are turned on alternately to obtain Figure 4 At this time, the a-phase buck-boost module is in boost mode, and the output voltage is higher than the input voltage. The on-off principles of the other two phases are the same. In this way, the three-phase AC power passes through the buck-boost module of the Y-type inverter and outputs AC power with a wide voltage range.

[0032] Afterwards, please refer to Figure 5 , Figure 6 , Figure 7 , Figure 8 , Fig. 9 , Fig.10 In the above-mentioned inverter process, taking the buck mode of the A-phase inverter process as an example, the output voltage is lower than the input voltage. Figure 5 , Figure 6 The working mode is 1. At this time, transistors T1 and T2 are continuously turned on, and transistors T3 and T4 are continuously turned off. The output voltage is Vdc / 2. Due to the conduction of transistors T1 and T2 and the AC circuit formed by diodes D1 and D2, a bidirectional circuit of the load current is formed. When the voltage on the clamping capacitor C3 is lower than zero, Figure 5 The dotted current loop shown in the figure is charged to zero. When the voltage of the clamping capacitor is greater than zero, Figure 6 The dashed current loop shown is discharged to zero by the load current. Figure 7 , Figure 8 It is working mode 2. At this time, transistors T2 and T4 are continuously turned on, transistors T1 and T3 are continuously turned off, and the output voltage is zero. D25-T2 and D2-C3-T4 form a bidirectional flow loop of the load current. When the voltage on the clamping capacitor C3 is lower than zero, Figure 7 The dotted line loop shown in the figure is charged to zero. When the voltage of the clamping capacitor is greater than zero, Figure 8 The dashed loop is shown discharged to zero by the load current. Figure 7It is working mode 3. At this time, transistors T1 and T3 are continuously turned on, transistors T2 and T4 are continuously turned off, and the output voltage is zero. The load current bidirectional flow loop is formed through T1-C3-D3 and T3-C3-D1. When the voltage on the clamping capacitor C3 is lower than zero, Figure 7 The dashed line loop shown is charging to zero. There is no discharge loop in this mode. Fig.10 The working mode is 4. At this time, transistors T3 and T4 are continuously turned on, and transistors T1 and T2 are continuously turned off. The output voltage is -Vdc / 2. Due to the conduction of T3 and T4 and the AC circuit formed by D3 and D4, a bidirectional flow circuit of the load current is formed. When the voltage on the clamping capacitor C3 is lower than zero, Fig.10 The dotted line circuit shown is charged to zero, and there is no discharge circuit in this mode. Through the alternating transformation of the four working modes, the inverter realizes three-level output while improving the waveform quality and reducing the overvoltage of the device.

[0033] The above is only a preferred implementation of this patent, but it is not intended to limit this patent. Technical personnel familiar with the field can make various changes and modifications without departing from the spirit and scope of this patent. Therefore, the scope of protection of this patent should be based on the definition of the claims.

Claims

1. A three-phase hybrid clamped three-level inverter with a wide voltage output range, comprising a DC voltage source module, a Y-type inverter module, a hybrid clamping module, a MOSFET control module, and a three-phase load module; characterized in that The output of the DC voltage source module is connected to the input of the Y-type inverter module, the hybrid clamp module is connected to the Y-type inverter module, the output of the MOSFET control module is connected to the input of the Y-type inverter module, and the output of the Y-type inverter module is connected to the input of the three-phase load module; the DC voltage source module includes a voltage source Vdc1, a voltage source Vdc2, a capacitor C i , ground port GND1; the Y-type inverter module includes a crystal switch tube T1, a crystal switch tube T2, a crystal switch tube T3, a crystal switch tube T4, a crystal switch tube T5, a crystal switch tube T6, a crystal switch tube T7, a crystal switch tube T8, a crystal switch tube T9, a crystal switch tube T10, a crystal switch tube T11, a crystal switch tube T12, a crystal switch tube T13, a crystal switch tube T14, a crystal switch tube T15, a crystal switch tube T16, a crystal switch tube T17, a crystal switch tube T18, a crystal switch tube T19, a crystal switch tube T20, a crystal switch tube T21, a crystal switch tube T22, a crystal switch tube T23, a crystal switch tube T24, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a diode D7, a diode D8, a diode D9, a diode D10, a diode D11, a diode D 12, diode D13, diode D14, diode D15, diode D16, diode D17, diode D18, diode D19, diode D20, diode D21, diode D22, diode D23, diode D24, inductor L1, inductor L2, inductor L3, capacitor C9, capacitor C10, capacitor C11; the hybrid clamping module includes diode D25, diode D26, diode D27, diode D28, diode D29, diode D30, diode D31, diode D32, diode D33, diode D34, diode D35, diode D36, inductor L9, capacitor C1, capacitor C2, capacitor C3, capacitor C4, capacitor C5, capacitor C6, capacitor C7, capacitor C8; the three-phase load module includes resistor R1, resistor R2, resistor R3, inductor L4, inductor L5, inductor L6.

2. A three-phase hybrid clamped three-level inverter with a wide voltage output range as claimed in claim 1, characterized in that: In the DC voltage source module, the voltage source Vdc1 and the voltage source Vdc2 are two identical DC voltage sources, the amplitude of which is Vdc / 2, and the positive electrode of the voltage source Vdc1 is connected to the capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the drain of transistor switch tube T1, the negative electrode is connected to the positive electrode of voltage source Vdc2 and the ground port GND1, and the negative electrode of voltage source Vdc2 is connected to the capacitor C i The cathode is connected to the cathode of capacitor C2 and the source of transistor switch tube T4.

3. A three-phase hybrid clamped three-level inverter with a wide voltage output range as claimed in claim 1, characterized in that: The MOSFET control module outputs 24 control signals, and the output interfaces are MOS tube T1, MOS tube T2, MOS tube T3, MOS tube T4, MOS tube T5, MOS tube T6, MOS tube T7, MOS tube T8, MOS tube T9, MOS tube T10, MOS tube T11, MOS tube T12, MOS tube T13, MOS tube T14, MOS tube T15, MOS tube T16, MOS tube T17, MOS tube T18, MOS tube T19, MOS tube T20, MOS tube T21, MOS tube T22, MOS tube T23, and MOS tube T24.

4. A three-phase hybrid clamped three-level inverter with a wide voltage output range as claimed in claim 1, characterized in that: In the Y-type inverter module, the gate of the transistor switch tube T1 is connected to the T1 output interface of the MOSFET control module, and the drain is connected to the capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the cathode of diode D1, the source electrode is connected to the drain of crystal switch tube T2, the anode of diode D1 and the positive electrode of capacitor C3, the gate of crystal switch tube T2 is connected to the T2 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T1, the cathode of diode D2 and the positive electrode of capacitor C3, the source electrode is connected to the drain of crystal switch tube T3, the anode of diode D2 and the positive electrode of inductor L1, the gate of crystal switch tube T3 is connected to the T3 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T2, the cathode of diode D3 and the positive electrode of inductor L1, the source electrode is connected to the drain of crystal switch tube T4, the anode of diode D3 and the negative electrode of capacitor C3, the gate of crystal switch tube T4 is connected to the T4 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T3, the anode of diode D3 and the negative electrode of capacitor C3, the source electrode is connected to the capacitor C i The cathode is connected to the cathode of capacitor C2 and the anode of diode D4, the gate of transistor switch tube T5 is connected to the T5 output interface of MOSFET control module, and the drain is connected to capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the cathode of diode D5, the source electrode is connected to the drain of crystal switch tube T6, the anode of diode D5 and the positive electrode of capacitor C4, the gate of crystal switch tube T6 is connected to the T6 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T5, the cathode of diode D6 and the positive electrode of capacitor C4, the source electrode is connected to the drain of crystal switch tube T7, the anode of diode D6 and the positive electrode of inductor L5, the gate of crystal switch tube T7 is connected to the T7 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T6, the cathode of diode D7 and the positive electrode of inductor L2, the source electrode is connected to the drain of crystal switch tube T8, the anode of diode D7 and the negative electrode of capacitor C4, the gate of crystal switch tube T8 is connected to the T8 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T7, the anode of diode D8 and the negative electrode of capacitor C4, the source electrode is connected to the capacitor C i The cathode is connected to the cathode of capacitor C2 and the anode of diode D8, the gate of transistor switch tube T9 is connected to the output interface of MOSFET control module T9, and the drain is connected to capacitor C i The positive electrode is connected to the positive electrode of capacitor C1 and the cathode of diode D9, the source electrode is connected to the drain of crystal switch tube T10, the anode of diode D9 and the positive electrode of capacitor C5, the gate of crystal switch tube T10 is connected to the T10 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T9, the cathode of diode D10 and the positive electrode of capacitor C5, the source electrode is connected to the drain of crystal switch tube T11, the anode of diode D10 and the positive electrode of inductor L3, the gate of crystal switch tube T11 is connected to the T11 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T10, the cathode of diode D11 and the positive electrode of inductor L3, the source electrode is connected to the drain of crystal switch tube T12, the anode of diode D11 and the negative electrode of capacitor C5, the gate of crystal switch tube T12 is connected to the T12 output interface of MOSFET control module, the drain electrode is connected to the source of crystal switch tube T11, the anode of diode D12 and the negative electrode of capacitor C5, the source electrode is connected to the capacitor C i The negative electrode is connected to the negative electrode of capacitor C2 and the anode of diode D12, the gate of crystal switch tube T13 is connected to the T13 output interface of MOSFET control module, the drain is connected to the cathode of diode D13 and the positive electrode of capacitor C9 and the positive electrode of resistor R1, the source is connected to the drain of crystal switch tube T14 and the anode of diode D13 and the positive electrode of capacitor C6, the gate of crystal switch tube T14 is connected to the T14 output interface of MOSFET control module, the drain is connected to the source of crystal switch tube T13 and the cathode of diode D14 and the positive electrode of capacitor C6, the source is connected to the drain of crystal switch tube T15 and diode D The anode of the transistor T14 is connected to the negative electrode of the inductor L1, the gate of the transistor T15 is connected to the output interface of the MOSFET control module T15, the drain is connected to the source of the transistor T14, the cathode of the diode D15 and the negative electrode of the inductor L1, the source is connected to the drain of the transistor T16, the anode of the diode D15 and the negative electrode of the capacitor C6, the gate of the transistor T16 is connected to the output interface of the MOSFET control module T16, the drain is connected to the source of the transistor T15, the cathode of the diode D16 and the negative electrode of the capacitor C6, the source is connected to the anode of the diode D16 and the negative electrode of the capacitor C2 and the capacitor C i The negative electrode is connected, the gate of the crystal switch tube T17 is connected to the T17 output interface of the MOSFET control module, the drain is connected to the cathode of the diode D17, the positive electrode of the capacitor C10 and the positive electrode of the resistor R2, the source is connected to the drain of the crystal switch tube T18, the anode of the diode D17 and the positive electrode of the capacitor C7, the gate of the crystal switch tube T18 is connected to the T18 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T17, the cathode of the diode D18 and the positive electrode of the capacitor C7, the source is connected to the drain of the crystal switch tube T19, the anode of the diode D18 and the inductor L 2, the gate of the crystal switch tube T19 is connected to the T19 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T18, the cathode of the diode D19 and the negative electrode of the inductor L2, the source is connected to the drain of the crystal switch tube T20, the anode of the diode D19 and the negative electrode of the capacitor C7, the gate of the crystal switch tube T20 is connected to the T20 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T19, the cathode of the diode D20 and the negative electrode of the capacitor C7, the source is connected to the anode of the diode D20, the negative electrode of the capacitor C2 and the capacitor C i The negative electrode is connected, the gate of the crystal switch tube T21 is connected to the T21 output interface of the MOSFET control module, the drain is connected to the cathode of the diode D21, the positive electrode of the capacitor C11 and the positive electrode of the resistor R3, the source is connected to the drain of the crystal switch tube T22, the anode of the diode D21 and the positive electrode of the capacitor C8, the gate of the crystal switch tube T22 is connected to the T22 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T21, the cathode of the diode D22 and the positive electrode of the capacitor C8, the source is connected to the drain of the crystal switch tube T23, the anode of the diode D22 and the inductor L 3, the gate of the crystal switch tube T23 is connected to the T23 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T22, the cathode of the diode D23 and the negative electrode of the inductor L3, the source is connected to the drain of the crystal switch tube T24, the anode of the diode D23 and the negative electrode of the capacitor C8, the gate of the crystal switch tube T24 is connected to the T24 output interface of the MOSFET control module, the drain is connected to the source of the crystal switch tube T23, the cathode of the diode D24 and the negative electrode of the capacitor C8, the source is connected to the anode of the diode D24, the negative electrode of the capacitor C2 and the capacitor C i Negative pole connected.

5. The three-phase hybrid clamped three-level inverter with a wide voltage output range as claimed in claim 1, characterized in that: In the hybrid clamping module, the cathode of the diode D25 is connected to the positive electrode of the capacitor C3, and the anode is connected to the cathode of the diode D26, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2. The cathode of the diode D26 is connected to the anode of the diode D25, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2, and the anode is connected to the negative electrode of the capacitor C3. The cathode of the diode D27 is connected to the positive electrode of the capacitor C4, and the anode is connected to the cathode of the diode D28, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2. The cathode of the diode D28 is connected to the anode of the diode D27, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2, and the anode is connected to the negative electrode of the capacitor C4. The cathode of the diode D29 is connected to the positive electrode of the capacitor C5, and the anode is connected to the cathode of the diode D30, the negative electrode of the capacitor C1 and the positive electrode of the capacitor C2, and the anode is connected to the negative electrode of the capacitor C5. , the cathode of diode D31 is connected to the positive electrode of capacitor C6, and the anode is connected to the cathode of diode D32, the negative electrode of capacitor C1 and the positive electrode of capacitor C2. The cathode of diode D32 is connected to the anode of diode D31, the negative electrode of capacitor C1 and the positive electrode of capacitor C2, and the anode is connected to the negative electrode of capacitor C6. The cathode of diode D33 is connected to the positive electrode of capacitor C7, and the anode is connected to the cathode of diode D34, the negative electrode of capacitor C1 and the positive electrode of capacitor C2. The cathode of diode D34 is connected to the anode of diode D33, the negative electrode of capacitor C1 and the positive electrode of capacitor C2, and the anode is connected to the negative electrode of capacitor C7. The cathode of diode D35 is connected to the positive electrode of capacitor C8, and the anode is connected to the cathode of diode D36, the negative electrode of capacitor C1 and the positive electrode of capacitor C2. The cathode of diode D36 is connected to the anode of diode D35, the negative electrode of capacitor C1 and the positive electrode of capacitor C2, and the anode is connected to the negative electrode of capacitor C8. The positive electrode of capacitor C1 is connected to capacitor C i The positive electrode is connected to the negative electrode of capacitor C2 and the capacitor C i Negative pole connected.

6. A three-phase hybrid clamped three-level inverter with a wide voltage output range as claimed in claim 1, characterized in that: In the three-phase load module, the positive electrode of resistor R1 is connected to the positive electrode of capacitor C9, and the negative electrode is connected to the positive electrode of inductor L4, the positive electrode of resistor R2 is connected to the positive electrode of capacitor C10, and the negative electrode is connected to the positive electrode of inductor L5, the positive electrode of resistor R3 is connected to the positive electrode of capacitor C11, and the negative electrode is connected to the positive electrode of inductor L6, and the negative electrode of inductor L4, the negative electrode of inductor L5, and the negative electrode of inductor L6 are connected in a star-shaped connection method with an ungrounded neutral point.

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