A ZVT soft-switching inverter with auxiliary inductor energy bidirectional transfer

Abstract

The present invention discloses an auxiliary inductor energy bidirectional transfer type ZVT soft switching inverter, including: an input power module, a low-frequency pole-changing bridge arm, a circuit filter and a freewheeling and output loop, a high-frequency chopping main switch tube, a bidirectional ZVT high-frequency auxiliary switch tube and an auxiliary resonant inductor and an energy recovery network; the present invention realizes the soft opening and soft closing of the high-frequency switch tube by controlling the resonant network through the auxiliary high-frequency power switch tube. With this design, the soft switching of the auxiliary power switch tube and the main circuit high-frequency power switch tube can be realized through the energy transfer between the resonant inductor and the main switch tube junction capacitor, and the energy can be recovered to the load side in time to reduce the loss. The switch tube adopts the combination of SPWM to realize high-low frequency mixed control, and the control method is relatively simple; the inductor current is freewheeling from the diode to avoid the bridge arm from passing directly, and realize the soft switching of all high-frequency power switch tubes, reduce the device loss, simple circuit structure, and require less passive components.

Description

Technical Field

[0001] The invention relates to the technical field of power electronic devices, and in particular to an auxiliary inductor energy bidirectional transfer type ZVT soft switch inverter. Background Art

[0002] As inverters continue to expand and develop in electric vehicles, new energy grid-connected power generation, uninterruptible power supplies and other application scenarios, the requirements for their switching frequency and power density are rapidly increasing. Therefore, the high-frequency and high-power density development of inverters is an inevitable trend. Considering the high-frequency development of inverter switching frequency, the process has the disadvantages of large switching loss, large inductive turn-off voltage spike, large capacitive turn-on current spike, diode recovery loss and lower efficiency. The above problems seriously hinder the improvement of inverter working power density, and soft switching technology is the main solution. Zero voltage conversion technology (ZVT) is an advanced resonant soft switching technology with a fixed operating frequency. It can achieve zero voltage turn-on of boost power MOSFET and zero current turn-off of boost diode during the switching conversion process. Applying soft switching technology to inverters can solve the problems of excessive switching loss, electromagnetic interference (EMI) and switching noise. Therefore, soft switching inverters have always received extensive attention and research. Traditional full-bridge inverter circuits have serious disadvantages such as direct-through hidden dangers, body diode freewheeling, large losses and reverse recovery problems, which reduce the reliability and efficiency of the converter. The hidden danger of bridge arm direct connection needs to be avoided by setting a dead zone. However, the dead zone has a natural constraint on the high frequency of the inverter, which is not conducive to the high integration and reliability of the inverter. Summary of the invention

[0003] Technical purpose: In view of the defects in the prior art, the present invention discloses a ZVT soft-switching inverter with auxiliary inductor energy bidirectional transfer. By adding a resonant inductor on the basis of a topological structure of a dual-Buck inverter without a bridge arm, energy is transferred through the resonance between the inductor and the capacitor, creating conditions for soft-on and soft-off of the switch tube, reducing high-frequency switching losses, and on the basis of providing soft switching conditions, the control mode is high-low frequency mixed control, and soft switching conditions are provided for all high-frequency power switch tubes in the circuit by adding a controllable auxiliary resonant branch, and the excess energy of the resonance is recovered. The technical problems of high-frequency noise and integration of the inverter are solved, and the technical purpose of high efficiency and high reliability is achieved.

[0004] Technical solution: In order to achieve the above technical objectives, the present invention adopts the following technical solution.

[0005] An auxiliary inductor energy bidirectional transfer type ZVT soft switch inverter, comprising: an input power module, a low-frequency pole-changing bridge arm, a circuit filter and a freewheeling and output loop, a high-frequency chopping main switch tube, a bidirectional ZVT high-frequency auxiliary switch tube and an auxiliary resonant inductor and an energy recovery network;

[0006] The input power module includes a DC power supply Ui, which is used to provide a DC voltage for the ZVT soft-switching inverter;

[0007] The low-frequency pole-changing bridge arm includes a full-bridge inverter, which is electrically connected to the DC power supply Ui, and is used to realize single-power bipolar inversion and output AC power frequency square waves for load-end voltage changes;

[0008] The positive terminal of the circuit filtering and freewheeling and output loop is connected to the midpoint of the left bridge arm of the full-bridge inverter in the low-frequency pole-changing bridge arm, and the negative terminal is connected to the input end of the high-frequency chopping main switch tube, which is used to filter the high-frequency square wave output by the high-frequency chopping main switch tube and then output an AC sine wave, and provide freewheeling when the high-frequency chopping main switch tube is turned off;

[0009] The input end of the high-frequency chopping main switch tube is connected to the negative end of the circuit filter and the freewheeling and output loop, and the output end of the high-frequency chopping main switch tube is connected to the midpoint of the right bridge arm of the full-bridge inverter in the low-frequency pole-changing bridge arm, so as to perform SPWM modulation on the AC power frequency square wave output by the low-frequency pole-changing bridge arm and output a high-frequency square wave;

[0010] The input end of the bidirectional ZVT high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network is connected to the negative end of the circuit filter and the freewheeling and output loop, and the input end of the high-frequency chopping main switch tube; the output end of the high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network is connected to the full-bridge inverter of the low-frequency pole-changing bridge arm and the output end of the high-frequency chopping main switch tube, so as to realize soft switching of the high-frequency chopping main switch tube, the high-frequency auxiliary switch tube, the auxiliary resonant inductor and the high-frequency switch tube in the energy recovery network.

[0011] Beneficial effects:

[0012] (1) The ZVT soft-switching inverter disclosed in the present invention is combined with SPWM to achieve high- and low-frequency mixed control. The control method has no dead time limitation. By controlling the resonant inductor on the auxiliary high-frequency power switch tube, the hardware circuit conditions for soft turning on and off of all switch tubes are provided. In addition, the newly added auxiliary resonant circuit has a simple structure and only requires one passive device.

[0013] (2) The inductor current flows through the switch tube to avoid the hidden danger of bridge arm direct conduction, so that the ZVT soft-switching inverter of the present invention does not need to consider the dead zone problem, which is convenient for improving the inverter switching frequency and high efficiency to achieve high integration, and a single filter inductor is more conducive to high integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A topological structure diagram of a ZVT soft-switching inverter with auxiliary inductor energy bidirectional transfer according to the present invention;

[0015] Figure 2It is a timing diagram of a driving signal, a switch tube voltage and current, a resonant inductor current, a junction capacitor current, and a diode current of an auxiliary inductor energy bidirectional transfer type ZVT soft switch inverter combined with SPWM hybrid control of the present invention;

[0016] Figures 3 to 9 Schematic diagram of seven working modes of the first stage of an auxiliary inductor energy bidirectional transfer type ZVT soft switching inverter of the present invention;

[0017] Figures 10 to 16 Schematic diagram of seven working modes of the second stage of an auxiliary inductor energy bidirectional transfer type ZVT soft switching inverter of the present invention;

[0018] Figures 17 to 23 Schematic diagram of seven working modes of the third stage of an auxiliary inductor energy bidirectional transfer type ZVT soft switching inverter of the present invention;

[0019] Figures 24 to 30 It is a schematic diagram of seven working modes of the fourth stage of an auxiliary inductor energy bidirectional transfer type ZVT soft switching inverter of the present invention. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] Example:

[0022] As attached Figure 1 As shown, an auxiliary inductor energy bidirectional transfer type ZVT soft switch inverter includes: an input power module 1, a low-frequency pole-changing bridge arm 2, a circuit filter and freewheeling and output loop 3, a high-frequency chopping main switch tube 4, a bidirectional ZVT high-frequency auxiliary switch tube and an auxiliary resonant inductor and an energy recovery network 5;

[0023] The input power module 1 includes a DC power supply Ui, which is used to provide a DC voltage for the ZVT soft-switching inverter;

[0024] The low-frequency pole-changing bridge arm 2 includes a full-bridge inverter, which is electrically connected to the DC power supply Ui, and is used to realize single-power bipolar inversion and output AC power frequency square waves for load-end voltage changes;

[0025] The positive terminal of the circuit filtering and freewheeling and output loop 3 is connected to the midpoint of the left bridge arm of the full-bridge inverter in the low-frequency pole-changing bridge arm 2, and the negative terminal is connected to the input end of the high-frequency chopping main switch tube 4, which is used to filter the high-frequency square wave output by the high-frequency chopping main switch tube 4 and then output an AC sine wave, and provide freewheeling when the high-frequency chopping main switch tube 4 is turned off;

[0026] The input end of the high-frequency chopping main switch tube 4 is connected to the negative terminal of the circuit filtering and freewheeling and output loop 3, and the output end of the high-frequency chopping main switch tube 4 is connected to the midpoint of the right bridge arm of the full-bridge inverter in the low-frequency pole-changing bridge arm 2, and is used to perform SPWM modulation on the AC power frequency square wave output by the low-frequency pole-changing bridge arm 2 and then output a high-frequency square wave, wherein the high-frequency switch tubes are all NMOS type;

[0027] The input end of the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and the energy recovery network 5 is connected to the negative end of the circuit filtering and freewheeling and output loop 3, and the input end of the high-frequency chopping main switch tube 4; the output end of the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and the energy recovery network 5 is connected to the full-bridge inverter of the low-frequency pole-changing bridge arm 2 and the output end of the high-frequency chopping main switch tube 4, which is used to realize soft switching of the high-frequency chopping main switch tube 4, the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and the high-frequency switch tube in the energy recovery network 5, wherein the high-frequency switch tubes are all NMOS type.

[0028] The low-frequency pole-changing bridge arm 2 includes a full-bridge inverter composed of a first power switch tube S1, a second power switch tube S2, a third power switch tube S3 and a fourth power switch tube S4. The source of the third power switch tube S3 and the drain of the fourth power switch tube S4 are connected to form a left bridge arm; the drain of the third power switch tube S3 and the source of the fourth power switch tube S4 are respectively connected to the positive electrode and the negative electrode of the DC power supply Ui; the source of the first power switch tube S1 and the drain of the second power switch tube S2 are connected to form a right bridge arm; the drain of the first power switch tube S1 and the source of the second power switch tube S2 are respectively connected to the positive electrode and the negative electrode of the DC power supply Ui;

[0029] The midpoint of the left bridge arm is connected to the positive terminal of the circuit filtering and freewheeling and output loop 3, that is, the load input side capacitor terminal in the circuit filtering and freewheeling and output loop 3, and the midpoint of the right bridge arm is connected to the output side of the high-frequency chopping main switch tube 4.

[0030] The circuit filtering and freewheeling and voltage output loop 3 includes a filter capacitor C f 、Filter inductor L f , a first diode D1, a second diode D2, wherein the filter capacitor C f 、Filter inductor L fIt is used to realize the circuit filtering function. The first diode D1 and the second diode D2 are used to realize the circuit freewheeling function; the filter capacitor C f One end of the filter capacitor C is used as the positive terminal of the circuit filter and freewheeling and output loop 3, and is connected to the midpoint of the left bridge arm of the low-frequency pole-changing bridge arm 2; the filter capacitor C f The other end of the filter inductor L f The positive terminal of the filter inductor is connected L f The negative terminal of the filter capacitor is used as the negative terminal of the circuit filter and freewheeling and output loop 3, and is connected to the input end of the high-frequency chopping main switch tube 4; the filter capacitor C f The two plates form the output end of the ZVT soft-switching inverter, that is, the output voltage Uo; the anode of the first diode D1 is connected to the cathode of the second diode D2 and serves as the midpoint of the freewheeling arm, and the midpoint of the freewheeling arm is connected to the filter inductor L f The cathode of the first diode D1 is connected to the positive electrode of the DC power supply Ui, and the anode of the second diode D2 is connected to the negative electrode of the DC power supply Ui.

[0031] The high-frequency chopping main switch tube 4 includes a fifth power switch tube Sa and a sixth power switch tube Sb. The drain of the fifth power switch tube Sa serves as the input end of the high-frequency chopping main switch tube 4, and is connected to the filter inductor in the circuit filtering and freewheeling and output loop 3. L f The negative terminal of the fifth power switch tube Sa is connected to the source of the sixth power switch tube Sb, and the drain of the sixth power switch tube Sb serves as the output terminal of the high-frequency chopping main switch tube 4. The equivalent capacitance of the fifth power switch tube Sa is the equivalent junction capacitance of the first switch tube. C 1 , the equivalent capacitance of the sixth power switch tube Sb is the equivalent junction capacitance of the second switch tube C 2 .

[0032] The bidirectional ZVT high-frequency auxiliary switch tube, auxiliary resonant inductor and energy recovery network 5 include an auxiliary resonant inductor Lr, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh power switch tube Qa, and an eighth power switch tube Qb;

[0033] One end of the auxiliary resonant inductor Lr serves as the input end of the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and energy recovery network 5, and is connected to the negative end of the circuit filtering and freewheeling and output loop 3 and the input end of the high-frequency chopping main switch tube 4; the other end of the auxiliary resonant inductor Lr is respectively connected to the anode of the fifth diode D5 and the cathode of the sixth diode D6; the anode of the third diode D3, the cathode of the fifth diode D5, and the drain of the seventh power switch tube Qa are connected to each other, and the cathode of the fourth diode D4, the anode of the sixth diode D6, and the source of the eighth power switch tube Qb are connected to each other; the cathode of the third diode D3 serves as the forward energy recovery end of the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and energy recovery network 5, and is connected to the positive electrode of the DC power supply Ui, and the anode of the fourth diode D4 serves as the bidirectional ZVT high-frequency auxiliary switch tube. The negative energy recovery end of the high-frequency auxiliary switch tube and the auxiliary resonant inductor and energy recovery network 5 is connected to the negative electrode of the DC power supply Ui; the source of the seventh power switch tube Qa and the drain of the eighth power switch tube Qb are connected, and serve as the output end of the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and energy recovery network 5, and the output end of the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and energy recovery network 5 is connected to the full-bridge inverter of the low-frequency variable pole bridge arm 2. Specifically, the output end of the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and energy recovery network 5 is connected to the midpoint of the right bridge arm of the low-frequency variable pole bridge arm 2, and the output end of the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and energy recovery network 5 is also connected to the output end of the high-frequency chopping main switch tube 4, that is, it is connected to the drain of the sixth power switch tube Sb. The equivalent capacitance of the seventh power switch tube Qa is the equivalent junction capacitance C3 of the third switch tube, and the equivalent capacitance of the eighth power switch tube Qb is the equivalent junction capacitance C4 of the fourth switch tube.

[0034] The bidirectional ZVT high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network 5 are used to realize controllable resonance to transfer the junction capacitance energy of the main high-frequency switch tube to the resonant inductor Lr, and recover it to the load through the energy recovery diode, so as to realize the soft switching of the high-frequency switch tubes: the fifth power switch tube Sa, the sixth power switch tube Sb, the seventh power switch tube Qa, and the eighth power switch tube Qb; the resonant branch is controlled by the auxiliary high-frequency switch tube to realize the soft opening and soft closing of the high-frequency switch tube, and the excess energy is recovered to the load through the diode.

[0035] The ZVT soft-switching inverter in the present invention mainly realizes the soft opening and soft shut-down of the high-frequency switch tube by controlling the resonant network through the auxiliary high-frequency power switch tube. With this design, the soft switching of the auxiliary power switch tube and the high-frequency power switch tube of the main circuit can be realized through the energy transfer between the resonant inductor and the junction capacitance of the main switch tube, and the energy is recovered to the load side in time to reduce the loss. The advantages of the ZVT soft-switching inverter structure in the present invention are: the high-frequency chopping main switch tube 4 and the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and the energy recovery network 5 are high-frequency controlled, and the low-frequency variable pole bridge arm 2 is low-frequency controlled, realizing the high-low frequency mixed control based on SPWM, and the control method is relatively simple; the inductor current is continuously flowing from the diode to avoid the bridge arm from passing directly, realizing the soft switching of all high-frequency power switch tubes, reducing device losses, simple circuit structure, and requiring fewer passive components.

[0036] The present invention obtains high-low frequency mixed control combined with SPWM through auxiliary high-frequency switch tubes, namely the seventh power switch tube Qa, the eighth power switch tube Qb and the main switch tube, namely the fifth power switch tube Sa and the sixth power switch tube Sb, and transfers the junction capacitance energy of the high-frequency power tubes Sa and Sb and recovers it to the load through the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and the energy recovery network 5, thereby realizing the soft switching of all high-frequency switch tubes. Through SPWM chopping control, the fifth power switch tube Sa switches at high frequency and the sixth power switch tube Sb is always on during the positive half cycle, and the sixth power switch tube Sb switches at high frequency and the fifth power switch tube Sa is always on during the negative half cycle, generating a high-frequency square wave and transmitting it to the output end, and outputting an AC sinusoidal waveform after passing through a filtering circuit.

[0037] The following is attached Figure 2 Ideal signal waveform, stage mode series Figure 3-Figure 30 , specifically describing the working principle and four-stage working modes of the ZVT soft-switching inverter of the present invention under SPWM control.

[0038] As attached Figure 3 To Attachment Fig. 9 As shown, in the first stage, S2 and S3 in the low-frequency pole-changing bridge arm 2 are constantly turned on, and the high-frequency chopping main switch tube 4 and the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and the Qa and Sa switch tubes in the energy recovery network 5 are based on SPWM high-frequency control. In the first stage, the current direction on the output filter inductor Lf is rightward, and the output voltage is positive on the left and negative on the right. The following is a description of the 7 modes of the first stage and the corresponding figures:

[0039] The first stage of working mode 1: Figure 3 The circuit topology shown corresponds to Figure 2In the period [t0, t1] shown, the third power switch tube S3, the second power switch tube S2, the first diode D1, and the fifth diode D5 are turned on, the seventh power switch tube Qa is turned on at zero current due to the auxiliary resonant inductor Lr, the fifth power switch tube Sa, the sixth power switch tube Sb, the first power switch tube S1, the fourth power switch tube S4, the second diode D2, the third diode D3, the fourth diode D4, the sixth diode D6, and the eighth power switch tube Qb are turned off, a part of the load side current IL continues to be conducted through the first diode D1, and a part of it flows through the seventh power switch tube Qa through the auxiliary resonant inductor Lr and the fifth diode D5 to the negative pole of the power supply. This stage lasts until the current of the first diode D1 drops to 0, the current direction on the output filter inductor Lf is rightward, the output voltage is positive on the left and negative on the right, and this stage ends.

[0040] Phase 1 working mode 2: Figure 4 The circuit topology shown corresponds to Figure 2 In the period [t1, t2] shown, the third power switch tube S3, the second power switch tube S2, the sixth power switch tube Sb, the seventh power switch tube Qa, and the fifth diode D5 are turned on, and the first power switch tube S1, the fourth power switch tube S4, the fifth power switch tube Sa, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the sixth diode D6, and the eighth power switch tube Qb are turned off. The load side current IL continues to flow through the seventh power switch tube Qa through the auxiliary resonant inductor Lr and the fifth diode D5. When the auxiliary inductor current is greater than the load current, it resonates with the equivalent junction capacitance C1 of the fifth power switch tube Sa, and the energy of the junction capacitance C1 is transferred to the auxiliary inductor Lr, and the current on the auxiliary inductor Lr reaches a peak value. The current direction on the output filter inductor Lf is rightward, and the output voltage is positive on the left and negative on the right, and this stage ends.

[0041] Phase 1 working mode 3: Figure 5 The circuit topology shown corresponds to Figure 2 In the period [t2, t3] shown in the figure, the third power switch tube S3, the second power switch tube S2, the fifth power switch tube Sa, the sixth power switch tube Sb, the seventh power switch tube Qa, and the fifth diode D5 are turned on, and the first power switch tube S1, the fourth power switch tube S4, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the sixth diode D6, and the eighth power switch tube Qb are turned off. At the moment t2, since the energy of the equivalent junction capacitance C1 of the fifth power switch tube Sa is completely released, zero voltage switching can be achieved. The main load side current flows through the seventh power switch tube Qa through the auxiliary resonant inductor Lr and the fifth diode D5 and the magnitude is constant. Part of the current flows through the fifth power switch tube Sa and the sixth power switch tube Sb and increases continuously. The current direction on the output filter inductor Lf is to the right, the output voltage is positive on the left and negative on the right, and this stage ends.

[0042] Phase 1 working mode 4: Figure 6 The circuit topology shown corresponds to Figure 2 In the period [t3, t4] shown in the figure, the third power switch tube S3, the second power switch tube S2, the fifth power switch tube Sa, the sixth power switch tube Sb, the third diode D3, and the fifth diode D5 are turned on, and the first power switch tube S1, the fourth power switch tube S4, the first diode D1, the second diode D2, the fourth diode D4, the sixth diode D6, and the eighth power switch tube Qb are turned off. Since the junction capacitor C3 of the seventh power switch tube Qa plays the role of buffering voltage, the zero voltage turn-off of the switch tube is realized. In this process, the auxiliary inductor current energy part establishes the voltage of the seventh power switch tube Qa, and part flows through the third diode D3 to be recovered to the load side. In this process, the current flowing through the auxiliary inductor gradually decreases to 0, and the current of the high-frequency chopping main switch tube gradually increases to be equal to the load current. The current direction on the output filter inductor Lf is to the right, the output voltage is positive on the left and negative on the right, and this stage ends.

[0043] Phase 1 working mode 5: Figure 7 The circuit topology shown corresponds to Figure 2 In the period [t4, t5] shown, the third power switch tube S3, the second power switch tube S2, the fifth power switch tube Sa, and the sixth power switch tube Sb are turned on, and the first power switch tube S1, the fourth power switch tube S4, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh power switch tube Qa, and the eighth power switch tube Qb are turned off. The current direction of the output filter inductor current output filter inductor Lf is rightward, the output voltage is positive on the left and negative on the right, and this stage ends.

[0044] Phase 1 working mode 6: Figure 8 The circuit topology shown corresponds to Figure 2 In the period [t5, t6] shown, the third power switch tube S3, the second power switch tube S2, and the sixth power switch tube Sb are turned on, and the first power switch tube S1, the fourth power switch tube S4, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh power switch tube Qa, and the eighth power switch tube Qb are turned off. The output filter inductor current flows through the equivalent junction capacitor C1 of the fifth power switch tube Sa. Due to the influence of the buffer capacitor C1, the fifth power switch tube Sa can achieve zero voltage shutdown, and part of the filter inductor current flows through the first diode D1 for continuous flow. The current direction on the output filter inductor Lf is to the right, the output voltage is positive on the left and negative on the right, and this stage ends.

[0045] Phase 1 working mode 7: Fig. 9 The circuit topology shown corresponds to Figure 2In the period [t6, t7] shown, the second power switch tube S2, the third power switch tube S3, and the first diode D1 are turned on, and the first power switch tube S1, the fourth power switch tube S4, the fifth power switch tube Sa, the sixth power switch tube Sb, the seventh power switch tube Qa, the eighth power switch tube Qb, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, and the sixth diode D6 are turned off. The filter inductor current flows through the third power switch tube S3 and the first diode D1 for continuous flow. The current direction on the output filter inductor Lf is rightward, the output voltage is positive on the left and negative on the right, and this stage ends.

[0046] As attached Fig.10 To Attachment Fig.16 As shown, in the second stage, S1 and S3 in the low-frequency pole-changing bridge arm 2 are constantly turned on, and the high-frequency chopping main switch tube 4 and the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and the Qa and Sa switch tubes in the energy recovery network 5 are based on SPWM high-frequency control. In the second stage, the current direction on the output filter inductor Lf is rightward, and the output voltage is negative on the left and positive on the right. The following is a description of the 7 modes of the second stage and the corresponding figures:

[0047] The second stage working mode 1: Fig.10 The circuit topology shown corresponds to Figure 2 In the period [t0, t1] shown, the first power switch tube S1, the third power switch tube S3, the first diode D1, and the fifth diode D5 are turned on, the seventh power switch tube Qa is turned on at zero current due to the auxiliary resonant inductor Lr, the second power switch tube S2, the fourth power switch tube S4, the fifth power switch tube Sa, the sixth power switch tube Sb, the second diode D2, the third diode D3, the fourth diode D4, the sixth diode D6, and the eighth power switch tube Qb are turned off, a part of the load side current continues to flow through the first diode D1 for freewheeling conduction, and a part of the load side current flows through the seventh power switch tube Qa through the auxiliary resonant inductor Lr and the fifth diode D5 to the positive pole of the power supply. This stage lasts until the current of the first diode D1 drops to 0, the current direction on the output filter inductor Lf is rightward, the output voltage is negative on the left and positive on the right, and this stage ends.

[0048] The second stage working mode 2: Fig.11 The circuit topology shown corresponds to Figure 2In the period [t1, t2] shown, the first power switch tube S1, the third power switch tube S3, the sixth power switch tube Sb, the seventh power switch tube Qa, and the fifth diode D5 are turned on, and the second power switch tube S2, the fourth power switch tube S4, the fifth power switch tube Sa, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the sixth diode D6, and the eighth power switch tube Qb are turned off. The load side current continues to flow through the seventh power switch tube Qa, the fifth diode D5, and the auxiliary resonant inductor Lr. When the auxiliary inductor current is greater than the load current, it resonates with the equivalent junction capacitance C1 of the fifth power switch tube Sa, and transfers the energy of the junction capacitance C1 to the auxiliary inductor Lr, and the current on the auxiliary inductor Lr reaches a peak value. The current direction on the output filter inductor Lf is rightward, and the output voltage is negative on the left and positive on the right, and this stage ends.

[0049] The second stage working mode 3: Fig.12 The circuit topology shown corresponds to Figure 2 In the period [t2, t3] shown in the figure, the first power switch tube S1, the third power switch tube S3, the fifth power switch tube Sa, the sixth power switch tube Sb, the seventh power switch tube Qa, and the fifth diode D5 are turned on, and the second power switch tube S2, the fourth power switch tube S4, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the sixth diode D6, and the eighth power switch tube Qb are turned off. At the moment t2, since the energy of the equivalent junction capacitance C1 of the fifth power switch tube Sa is completely released, zero voltage switching can be achieved. The main load side current flows through the seventh power switch tube Qa, the fifth diode D5, and the auxiliary resonant inductor Lr and the magnitude is constant. Part of the current flows through the fifth power switch tube Sa and the sixth power switch tube Sb and continues to increase. The current direction on the output filter inductor Lf is rightward, the output voltage is negative on the left and positive on the right, and this stage ends.

[0050] The second stage working mode 4: Fig.13 The circuit topology shown corresponds to Figure 2In the period [t3, t4] shown in the figure, the first power switch tube S1, the third power switch tube S3, the fifth power switch tube Sa, the sixth power switch tube Sb, the third diode D3, and the fifth diode D5 are turned on, and the second power switch tube S2, the fourth power switch tube S4, the first diode D1, the second diode D2, the fourth diode D4, the sixth diode D6, and the eighth power switch tube Qb are turned off. Since the junction capacitor C3 of the seventh power switch tube Qa plays the role of buffering voltage, the zero voltage turn-off of the switch tube is realized. In this process, the auxiliary inductor current energy part establishes the voltage of the seventh power switch tube Qa, and part flows through the third diode D3 to be recovered to the load side. In this process, the current flowing through the auxiliary inductor gradually decreases to 0, and the current of the high-frequency chopping main switch tube gradually increases to be equal to the load current. The current direction on the output filter inductor Lf is to the right, the output voltage is negative on the left and positive on the right, and this stage ends.

[0051] Second stage working mode 5: Fig.14 The circuit topology shown corresponds to Figure 2 In the period [t4, t5] shown, the first power switch tube S1, the third power switch tube S3, the fifth power switch tube Sa, and the sixth power switch tube Sb are turned on, and the second power switch tube S2, the fourth power switch tube S4, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh power switch tube Qa, and the eighth power switch tube Qb are turned off. The current direction on the output filter inductor Lf is rightward, the output voltage is negative on the left and positive on the right, and this stage ends.

[0052] The second stage working mode 6: Fig.15 The circuit topology shown corresponds to Figure 2 In the period [t5, t6] shown, the first power switch tube S1, the third power switch tube S3, the sixth power switch tube Sb, and the first diode D1 are turned on, and the second power switch tube S2, the fourth power switch tube S4, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh power switch tube Qa, and the eighth power switch tube Qb are turned off. The output filter inductor current flows through the equivalent junction capacitor C1 of the fifth power switch tube Sa. Due to the influence of the buffer capacitor C1, the fifth power switch tube Sa can achieve zero voltage shutdown, and part of the filter inductor current flows through the first diode D1 for continuous flow. The current direction on the output filter inductor Lf is rightward, the output voltage is negative on the left and positive on the right, and this stage ends.

[0053] Second stage working mode 7: Fig.16 The circuit topology shown corresponds to Figure 2In the period [t6, t7] shown, the first power switch tube S1, the third power switch tube S3, and the first diode D1 are turned on, and the second power switch tube S2, the fourth power switch tube S4, the fifth power switch tube Sa, the sixth power switch tube Sb, the seventh power switch tube Qa, the eighth power switch tube Qb, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, and the sixth diode D6 are turned off. The filter inductor current flows through the third power switch tube S3 and the first diode D1 for continuous flow. The current direction on the output filter inductor Lf is to the right, the output voltage is negative on the left and positive on the right, and this stage ends.

[0054] As attached Fig.17 To Attachment Fig.23 As shown, in the third stage, S1 and S4 in the low-frequency pole-changing bridge arm 2 are constantly turned on, and the high-frequency chopping main switch tube 4 and the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and the Qb and Sb switch tubes in the energy recovery network 5 are based on SPWM high-frequency control. In the third stage, the current direction on the output filter inductor Lf is to the left, and the output voltage is negative on the left and positive on the right. The following is a description of the 7 modes of the third stage and the corresponding figures:

[0055] The third stage working mode 1: Fig.17 The circuit topology shown corresponds to Figure 2 In the period [t0, t1] shown, the first power switch tube S1, the fourth power switch tube S4, the second diode D2, and the sixth diode D6 are turned on, and the eighth power switch tube Qb is turned on at zero current due to the auxiliary resonant inductor Lr. The second power switch tube S2, the third power switch tube S3, the fifth power switch tube Sa, the sixth power switch tube Sb, the first diode D1, the third diode D3, the fourth diode D4, the fifth diode D5, and the seventh power switch tube Qa are turned off. A part of the load side current continues to flow through the second diode D2, and a part of the current flows through the eighth power switch tube Qb through the auxiliary resonant inductor Lr and the sixth diode D6 to the negative pole of the power supply. This stage lasts until the current of the second diode D2 drops to 0. The current direction on the output filter inductor Lf is to the left, the output voltage is negative on the left and positive on the right, and this stage ends.

[0056] The third stage working mode 2: Fig.18 The circuit topology shown corresponds to Figure 2In the period [t1, t2] shown, the first power switch tube S1, the fourth power switch tube S4, the fifth power switch tube Sa, the eighth power switch tube Qb, and the sixth diode D6 are turned on, and the second power switch tube S2, the third power switch tube S3, the sixth power switch tube Sb, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, and the seventh power switch tube Qa are turned off. The load side current continues to flow through the eighth power switch tube Qb, the sixth diode D6, and the auxiliary resonant inductor Lr. When the auxiliary inductor current is greater than the load current, it resonates with the equivalent junction capacitance C2 of the sixth power switch tube Sb, and the energy of the junction capacitance C2 is transferred to the auxiliary inductor Lr, and the current on the auxiliary inductor Lr reaches a peak value. The current direction on the output filter inductor Lf is to the left, and the output voltage is negative on the left and positive on the right, and this stage ends.

[0057] The third stage working mode 3: Fig.19 The circuit topology shown corresponds to Figure 2 In the period [t2, t3] shown in the figure, the first power switch tube S1, the fourth power switch tube S4, the fifth power switch tube Sa, the sixth power switch tube Sb, the eighth power switch tube Qb, and the sixth diode D6 are turned on, and the second power switch tube S2, the third power switch tube S3, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, and the seventh power switch tube Qa are turned off. At the moment t2, since the energy of the equivalent junction capacitance C2 of the sixth power switch tube Sb is completely released, zero voltage switching can be achieved. The main load side current flows through the eighth power switch tube Qb, the sixth diode D6, and the auxiliary resonant inductor Lr and the magnitude is constant. Part of the current flows through the fifth power switch tube Sa and the sixth power switch tube Sb and increases continuously. The current direction on the output filter inductor Lf is to the left, the output voltage is negative on the left and positive on the right, and this stage ends.

[0058] The third stage working mode 4: Fig. 20 The circuit topology shown corresponds to Figure 2In the period [t3, t4] shown in the figure, the first power switch tube S1, the fourth power switch tube S4, the fifth power switch tube Sa, the sixth power switch tube Sb, the fourth diode D4, and the sixth diode D6 are turned on, and the second power switch tube S2, the third power switch tube S3, the first diode D1, the second diode D2, the third diode D3, the fifth diode D5, and the seventh power switch tube Qa are turned off. Since the junction capacitor C4 of the eighth power switch tube Qb plays the role of buffering voltage, the zero voltage turn-off of the switch tube is realized. In this process, the auxiliary inductor current energy part establishes the voltage of the eighth power switch tube Qb, and part flows through the fourth diode D4 to be recovered to the load side. In this process, the current flowing through the auxiliary inductor gradually decreases to 0, and the current of the high-frequency chopping main switch tube gradually increases to be equal to the load current. The current direction on the output filter inductor Lf is to the left, the output voltage is negative on the left and positive on the right, and this stage ends.

[0059] The third stage working mode 5: Fig.21 The circuit topology shown corresponds to Figure 2 In the period [t4, t5] shown, the first power switch tube S1, the fourth power switch tube S4, the fifth power switch tube Sa, and the sixth power switch tube Sb are turned on, and the second power switch tube S2, the third power switch tube S3, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh power switch tube Qa, and the eighth power switch tube Qb are turned off. The current direction on the output filter inductor Lf is to the left, the output voltage is negative on the left and positive on the right, and this stage ends.

[0060] The third stage working mode 6: Fig. 22 The circuit topology shown corresponds to Figure 2 In the period [t5, t6] shown, the first power switch tube S1, the fourth power switch tube S4, the fifth power switch tube Sa, and the second diode D2 are turned on, and the second power switch tube S2, the third power switch tube S3, the first diode D1, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh power switch tube Qa, and the eighth power switch tube Qb are turned off. The output filter inductor current flows through the equivalent junction capacitor C2 of the sixth power switch tube Sb. Due to the influence of the buffer capacitor C2, the sixth power switch tube Sb can achieve zero voltage shutdown, and part of the filter inductor current flows through the second diode D2 for continuous flow. The current direction on the output filter inductor Lf is to the left, the output voltage is negative on the left and positive on the right, and this stage ends.

[0061] The third stage working mode 7: Fig.23 The circuit topology shown corresponds to Figure 2In the period [t6, t7] shown, the first power switch tube S1, the fourth power switch tube S4, and the second diode D2 are turned on, and the second power switch tube S2, the third power switch tube S3, the fifth power switch tube Sa, the sixth power switch tube Sb, the seventh power switch tube Qa, the eighth power switch tube Qb, the first diode D1, the third diode D3, the fourth diode D4, the fifth diode D5, and the sixth diode D6 are turned off. The filter inductor current flows through the fourth power switch tube S4 and the second diode D2 for freewheeling, and the current direction on the output filter inductor Lf is to the left, the output voltage is negative on the left and positive on the right, and this stage ends.

[0062] As attached Fig.24 To Attachment Fig.30 As shown, in the fourth stage, S2 and S4 in the low-frequency pole-changing bridge arm 2 are constantly turned on, and the high-frequency chopping main switch tube 4 and the bidirectional ZVT high-frequency auxiliary switch tube and the auxiliary resonant inductor and the Qb and Sb switch tubes in the energy recovery network 5 are based on SPWM high-frequency control. In the fourth stage, the current direction on the output filter inductor Lf is to the left, and the output voltage is positive on the left and negative on the right. The following is a description of the 7 modes of the fourth stage and the corresponding figures:

[0063] The fourth stage of working mode 1: Fig.24 The circuit topology shown corresponds to Figure 2 In the period [t0, t1] shown, the second power switch tube S2, the fourth power switch tube S4, the second diode D2, and the sixth diode D6 are turned on, and the eighth power switch tube Qb is turned on at zero current due to the auxiliary resonant inductor Lr. The first power switch tube S1, the third power switch tube S3, the fifth power switch tube Sa, the sixth power switch tube Sb, the first diode D1, the third diode D3, the fourth diode D4, the fifth diode D5, and the seventh power switch tube Qa are turned off. A part of the load side current continues to flow through the second diode D2, and a part of the current flows through the eighth power switch tube Qb through the auxiliary resonant inductor Lr and the sixth diode D6 to the negative pole of the power supply. This stage lasts until the current of the second diode D2 drops to 0. The current direction on the output filter inductor Lf is to the left, the output voltage is positive on the left and negative on the right, and this stage ends.

[0064] The fourth stage of working mode 2: Fig.25 The circuit topology shown corresponds to Figure 2In the period [t1, t2] shown, the second power switch tube S2, the fourth power switch tube S4, the fifth power switch tube Sa, the eighth power switch tube Qb, and the sixth diode D6 are turned on, and the first power switch tube S1, the third power switch tube S3, the sixth power switch tube Sb, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, and the seventh power switch tube Qa are turned off. The load side current continues to flow through the eighth power switch tube Qb, the sixth diode D6, and the auxiliary resonant inductor Lr. When the auxiliary inductor current is greater than the load current, it resonates with the equivalent junction capacitance C2 of the sixth power switch tube Sb, and the energy of the junction capacitance C2 is transferred to the auxiliary inductor Lr, and the current on the auxiliary inductor Lr reaches a peak value. The current direction on the output filter inductor Lf is to the left, the output voltage is positive on the left and negative on the right, and this stage ends.

[0065] The fourth stage of working mode 3: Fig.26 The circuit topology shown corresponds to Figure 2 In the period [t2, t3] shown in the figure, the second power switch tube S2, the fourth power switch tube S4, the fifth power switch tube Sa, the sixth power switch tube Sb, the eighth power switch tube Qb, and the sixth diode D6 are turned on, and the first power switch tube S1, the third power switch tube S3, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, and the seventh power switch tube Qa are turned off. At the moment t2, since the energy of the equivalent junction capacitance C2 of the sixth power switch tube Sb is completely released, zero voltage switching can be achieved. The main load side current flows through the eighth power switch tube Qb, the sixth diode D6, and the auxiliary resonant inductor Lr and the magnitude is constant. Part of the current flows through the fifth power switch tube Sa and the sixth power switch tube Sb and increases continuously. The current direction on the output filter inductor Lf is to the left, the output voltage is positive on the left and negative on the right, and this stage ends.

[0066] The fourth stage of working mode 4: Fig. 27 The circuit topology shown corresponds to Figure 2In the period [t3, t4] shown in the figure, the second power switch tube S2, the fourth power switch tube S4, the fifth power switch tube Sa, the sixth power switch tube Sb, the fourth diode D4, and the sixth diode D6 are turned on, and the first power switch tube S1, the third power switch tube S3, the first diode D1, the second diode D2, the third diode D3, the fifth diode D5, and the seventh power switch tube Qa are turned off. Since the junction capacitor C4 of the eighth power switch tube Qb plays the role of buffering voltage, the zero voltage turn-off of the switch tube is realized. In this process, the auxiliary inductor current energy part establishes the voltage of the eighth power switch tube Qb, and part flows through the fourth diode D4 to be recovered to the load side. In this process, the current flowing through the auxiliary inductor gradually decreases to 0, and the current of the high-frequency chopping main switch tube gradually increases to be equal to the load current. The current direction on the output filter inductor Lf is to the left, the output voltage is positive on the left and negative on the right, and this stage ends.

[0067] The fourth stage of working mode 5: Fig.28 The circuit topology shown corresponds to Figure 2 In the period [t4, t5] shown, the second power switch tube S2, the fourth power switch tube S4, the fifth power switch tube Sa, and the sixth power switch tube Sb are turned on, and the first power switch tube S1, the third power switch tube S3, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh power switch tube Qa, and the eighth power switch tube Qb are turned off. The current direction on the output filter inductor Lf is to the left, the output voltage is positive on the left and negative on the right, and this stage ends.

[0068] The fourth stage of working mode 6: Fig.29 The circuit topology shown corresponds to Figure 2 In the period [t5, t6] shown, the second power switch tube S2, the fourth power switch tube S4, the fifth power switch tube Sa, and the second diode D2 are turned on, and the first power switch tube S1, the third power switch tube S3, the first diode D1, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh power switch tube Qa, and the eighth power switch tube Qb are turned off. The output filter inductor current flows through the equivalent junction capacitor C2 of the sixth power switch tube Sb. Due to the influence of the buffer capacitor C2, the sixth power switch tube Sb can achieve zero voltage shutdown, and part of the filter inductor current flows through the second diode D2 for continuous flow. The current direction on the output filter inductor Lf is to the left, the output voltage is positive on the left and negative on the right, and this stage ends.

[0069] The fourth stage of working mode 7: Fig.30 The circuit topology shown corresponds to Figure 2In the period [t6, t7] shown, the second power switch tube S2, the fourth power switch tube S4, and the second diode D2 are turned on, and the first power switch tube S1, the third power switch tube S3, the fifth power switch tube Sa, the sixth power switch tube Sb, the seventh power switch tube Qa, the eighth power switch tube Qb, the first diode D1, the third diode D3, the fourth diode D4, the fifth diode D5, and the sixth diode D6 are turned off. The filter inductor current flows through the fourth power switch tube S4 and the second diode D2 for freewheeling, and the current direction on the output filter inductor Lf is to the left, the output voltage is positive on the left and negative on the right, and this stage ends.

[0070] Through the analysis of the working mode of the circuit, we can know that the present invention realizes the soft opening and soft closing of all high-frequency power switch tubes in the main circuit through the bidirectional ZVT high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network. The ZVT soft switching inverter has the following advantages:

[0071] (1) Combined with SPWM to achieve high and low frequency control, the control method is relatively simple.

[0072] (2) The inductor current flows through the diode, and the inverter does not have the problem of bridge arm shoot-through.

[0073] (3) Realize ZVT soft switching of all high-frequency switching tubes to reduce device losses.

[0074] (4) The circuit structure is simple and soft switching requires only one passive device.

[0075] The "first" and "second" in the names of "first" and "second" mentioned in the embodiments of this application are only used as name identifications and do not represent their importance rankings.

[0076] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An auxiliary inductor energy bidirectional transfer type ZVT soft switching inverter, characterized in that: include: Input power module, low-frequency pole-changing bridge arm, circuit filtering and freewheeling and output circuit, high-frequency chopping main switch tube, bidirectional ZVT high-frequency auxiliary switch tube and auxiliary resonant inductor and energy recovery network; The input power module includes a DC power supply Ui, which is used to provide a DC voltage for the ZVT soft-switching inverter; The low-frequency pole-changing bridge arm includes a full-bridge inverter, which is electrically connected to the DC power supply Ui, and is used to realize single-power bipolar inversion and output AC power frequency square waves for load-end voltage changes; The positive terminal of the circuit filtering and freewheeling and output loop is connected to the midpoint of the left bridge arm of the full-bridge inverter in the low-frequency pole-changing bridge arm, and the negative terminal is connected to the input end of the high-frequency chopping main switch tube, which is used to filter the high-frequency square wave output by the high-frequency chopping main switch tube and then output an AC sine wave, and provide freewheeling when the high-frequency chopping main switch tube is turned off; The input end of the high-frequency chopping main switch tube is connected to the negative end of the circuit filter and the freewheeling and output loop, and the output end of the high-frequency chopping main switch tube is connected to the midpoint of the right bridge arm of the full-bridge inverter in the low-frequency pole-changing bridge arm, so as to perform SPWM modulation on the AC power frequency square wave output by the low-frequency pole-changing bridge arm and output a high-frequency square wave; The input end of the bidirectional ZVT high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network is connected to the negative end of the circuit filter and the freewheeling and output loop, and the input end of the high-frequency chopping main switch tube; the output end of the high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network is connected to the full-bridge inverter of the low-frequency pole-changing bridge arm and the output end of the high-frequency chopping main switch tube, so as to realize the soft switching of the high-frequency chopping main switch tube, the high-frequency auxiliary switch tube, the auxiliary resonant inductor and the high-frequency switch tube in the energy recovery network; the bidirectional ZVT high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network include an auxiliary resonant inductor Lr, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh power switch tube Qa, and an eighth power switch tube Qb; One end of the auxiliary resonant inductor Lr serves as the input end of the high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network, and is connected to the negative end of the circuit filter and the freewheeling and output loop, and the input end of the high-frequency chopping main switch tube; the other end of the auxiliary resonant inductor Lr is respectively connected to the anode of the fifth diode D5 and the cathode of the sixth diode D6; the anode of the third diode D3, the cathode of the fifth diode D5, and the drain of the seventh power switch tube Qa are connected to each other, and the cathode of the fourth diode D4, the anode of the sixth diode D6, and the source of the eighth power switch tube Qb are connected to each other; the cathode of the third diode D3 serves as the high-frequency auxiliary switch tube and The positive energy recovery end of the auxiliary resonant inductor and the energy recovery network is connected to the positive electrode of the DC power supply Ui, and the anode of the fourth diode D4 serves as the negative energy recovery end of the high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network, and is connected to the negative electrode of the DC power supply Ui; the source of the seventh power switch tube Qa and the drain of the eighth power switch tube Qb are connected, and serve as the output end of the high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network, and the output end of the high-frequency auxiliary switch tube, the auxiliary resonant inductor and the energy recovery network is connected to the midpoint of the right bridge arm of the full-bridge inverter in the low-frequency pole-changing bridge arm and the output end of the high-frequency chopping main switch tube.

2. The auxiliary inductor energy bidirectional transfer type ZVT soft switching inverter according to claim 1, characterized in that: The low-frequency pole-changing bridge arm includes a full-bridge inverter composed of a first power switch tube S1, a second power switch tube S2, a third power switch tube S3 and a fourth power switch tube S4. The source of the third power switch tube S3 and the drain of the fourth power switch tube S4 are connected to form a left bridge arm; the drain of the third power switch tube S3 and the source of the fourth power switch tube S4 are respectively connected to the positive electrode and the negative electrode of the DC power supply Ui; the source of the first power switch tube S1 and the drain of the second power switch tube S2 are connected to form a right bridge arm; the drain of the first power switch tube S1 and the source of the second power switch tube S2 are respectively connected to the positive electrode and the negative electrode of the DC power supply Ui.

3. The auxiliary inductor energy bidirectional transfer type ZVT soft switching inverter according to claim 1, characterized in that: The circuit filtering and freewheeling and output circuit includes a filter capacitor C f 、Filter inductor L f , first diode D1, second diode D2; filter capacitor C f One end of the filter capacitor C is used as the positive terminal of the circuit filter and freewheeling and output circuit, and is connected to the midpoint of the left bridge arm of the low-frequency pole-changing bridge arm; the filter capacitor C f The other end of the filter inductor L f The positive terminal of the filter inductor is connected L f The negative terminal of the circuit is used as the negative terminal of the circuit filtering and freewheeling and output loop, and is connected to the input end of the high-frequency chopping main switch tube; the anode of the first diode D1 is connected to the cathode of the second diode D2 and serves as the midpoint of the freewheeling arm, and the midpoint of the freewheeling arm is connected to the filter inductor L f The cathode of the first diode D1 is connected to the positive pole of the DC power supply Ui, and the anode of the second diode D2 is connected to the negative pole of the DC power supply Ui.

4. The auxiliary inductor energy bidirectional transfer type ZVT soft switching inverter according to claim 1, characterized in that: The high-frequency chopping main switch tube includes a fifth power switch tube Sa and a sixth power switch tube Sb. The drain of the fifth power switch tube Sa serves as the input end of the high-frequency chopping main switch tube, and is connected to the filter inductor in the circuit filtering and freewheeling and output loops. L f The negative terminal of the fifth power switch tube Sa is connected to the source of the sixth power switch tube Sb, and the drain of the sixth power switch tube Sb serves as the output end of the high-frequency chopping main switch tube.

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