A single-phase sine wave inverter soft switching circuit and device based on controllable inductance

Abstract

This invention provides a soft-switching circuit and device for a single-phase sinusoidal inverter based on a controllable inductor, including a phase-shifted full-bridge converter unit, a variable inductor unit, a high-frequency transformer, a frequency converter unit, and a filter unit. The output terminal of the phase-shifted full-bridge converter unit is electrically connected to the input terminal of the variable inductor unit, the output terminal of the phase-shifted full-bridge converter unit is electrically connected to the primary winding of the high-frequency transformer, the secondary winding of the high-frequency transformer is electrically connected to the input terminal of the frequency converter unit, the input terminal of the filter unit is electrically connected to the output terminal of the frequency converter unit, and the output terminal of the filter unit is electrically connected to the secondary winding of the high-frequency transformer. The control terminals of the phase-shifted full-bridge converter unit, the frequency converter unit, and the variable inductor unit are electrically connected to the output terminal of a controller. This invention aims to solve the problem in existing high-frequency chain inverters where the leading and lagging arms alternate only once within one frequency converter cycle, making it difficult to achieve soft switching for most of the operating time of each switching transistor in the phase-shifted full-bridge converter.

Description

Technical Field

[0001] This invention relates to the field of high-frequency link inverter technology, specifically to a soft-switching circuit and device for a single-phase sinusoidal inverter based on a controllable inductor. Background Technology

[0002] High-frequency link inverter technology refers to replacing the power frequency transformer in low-frequency inverter technology with a high-frequency transformer, thereby overcoming the shortcomings of low-frequency inverter technology and significantly improving the inverter's performance. Existing high-frequency link inverters typically employ SPWPM (Sinusoidal Pulse Width and Position Modulation) modulation strategies. Later, to overcome the problems and shortcomings of traditional SPWPM modulation strategies, various improved SPWPM modulation strategies were developed. Although these SPWPM modulation strategies and their improved versions utilize LC resonance to inject resonant current into the midpoint of the phase-shifted full-bridge arms, creating conditions for zero-voltage turn-on of the phase-shifted full-bridge converter's switching transistors, the phase-shifted full-bridge converter's switching transistors still operate in hard-switching mode most of the time, resulting in significant switching losses.

[0003] Please see Figure 1 This paper borrows the method of widening the soft-switching range of the lagging arm in a DC / DC phase-shifted full-bridge converter to achieve soft switching in the phase-shifted full-bridge circuit section of a high-frequency link inverter. The auxiliary network consists of La1, Ca1, La2, and Ca2. Resonant current is injected into the midpoint of the phase-shifted full-bridge arm using LC resonance, creating conditions for zero-voltage turn-on of the switching transistors M1, M2, M3, and M4 of the phase-shifted full-bridge converter. However, the resonant energy must be large enough to guarantee a wide range of soft-switching operation, resulting in excessive reactive circulating current. Even with an improved SPWPM modulation strategy in the software, the leading and lagging arms in the high-frequency link inverter still alternate once within one cycle, making it difficult to achieve soft switching for most of the operating time of each switching transistor in the phase-shifted full-bridge converter.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] The purpose of this invention is to provide a soft-switching circuit and device for a single-phase sinusoidal inverter based on a controllable inductor, which can effectively solve the problem that the leading arm and lagging arm of the existing high-frequency chain inverter will alternate once within one cycle of the conversion, making it difficult for each switching transistor of the phase-shifted full-bridge converter to achieve soft switching for most of the working time.

[0006] This invention discloses a soft-switching circuit for a single-phase sinusoidal inverter based on a controllable inductor, comprising a phase-shifting full-bridge converter unit, a variable inductor unit, a high-frequency transformer, a frequency converter unit, and a filter unit.

[0007] Specifically, the output terminal of the phase-shifted full-bridge converter is electrically connected to the input terminal of the variable inductor unit, the output terminal of the phase-shifted full-bridge converter is electrically connected to the primary winding of the high-frequency transformer, the secondary winding of the high-frequency transformer is electrically connected to the input terminal of the frequency converter, the input terminal of the filter unit is electrically connected to the output terminal of the frequency converter, and the output terminal of the filter unit is electrically connected to the secondary winding of the high-frequency transformer.

[0008] The control terminals of the phase-shifting full-bridge converter, the frequency converter, and the variable inductor are electrically connected to the output terminal of the controller.

[0009] Preferably, the phase-shifting full-bridge converter unit includes a DC voltage source, a first bridge arm, and a second bridge arm. The first bridge arm is located on both sides of the DC voltage source, and the second bridge arm is located on both sides of the first bridge arm. The center of the first bridge arm is electrically connected to the same-name terminal of the first winding of the high-frequency transformer, and the center of the second bridge arm is electrically connected to the opposite-name terminal of the first winding of the high-frequency transformer. The center of the first bridge arm and the center of the second bridge arm are electrically connected to the input terminal of the variable inductor unit, and the control terminals of the first bridge arm and the second bridge arm are electrically connected to the output terminal of the controller.

[0010] Preferably, the first bridge arm includes a first phase-shifted full-bridge main bridge arm switch, a first parasitic capacitor, a third phase-shifted full-bridge main bridge arm switch, and a third parasitic capacitor;

[0011] Wherein, the positive terminal of the DC voltage source is electrically connected to the collector of the first phase-shifted full-bridge main arm switch, the emitter of the first phase-shifted full-bridge main arm switch is electrically connected to the collector of the third phase-shifted full-bridge main arm switch, the emitter of the third phase-shifted full-bridge main arm switch is electrically connected to the negative terminal of the DC voltage source, one end of the first parasitic capacitor is electrically connected to the collector of the first phase-shifted full-bridge main arm switch, and the other end of the first parasitic capacitor is electrically connected to the emitter of the first phase-shifted full-bridge main arm switch, and the third parasitic capacitor... One end of the third parasitic capacitor is electrically connected to the collector of the third phase-shifted full-bridge main arm switch, and the other end of the third parasitic capacitor is electrically connected to the emitter of the third phase-shifted full-bridge main arm switch. The emitter of the first phase-shifted full-bridge main arm switch is electrically connected to the same-name terminal of the first winding of the high-frequency transformer. The emitter of the first phase-shifted full-bridge main arm switch is electrically connected to the input terminal of the variable inductor unit. The control terminals of the first phase-shifted full-bridge main arm switch and the third phase-shifted full-bridge main arm switch are electrically connected to the output terminal of the controller.

[0012] Preferably, the second bridge arm includes a second phase-shifted full-bridge main bridge arm switch, a fourth phase-shifted full-bridge main bridge arm switch, a second parasitic capacitor, and a fourth parasitic capacitor;

[0013] Wherein, the positive terminal of the DC voltage source is electrically connected to the collector of the second phase-shifted full-bridge main arm switch, the emitter of the second phase-shifted full-bridge main arm switch is electrically connected to the collector of the fourth phase-shifted full-bridge main arm switch, the emitter of the fourth phase-shifted full-bridge main arm switch is electrically connected to the negative terminal of the DC voltage source, one end of the second parasitic capacitor is electrically connected to the collector of the second phase-shifted full-bridge main arm switch, and the other end of the second parasitic capacitor is electrically connected to the emitter of the second phase-shifted full-bridge main arm switch, and the fourth parasitic capacitor... One end of the fourth parasitic capacitor is electrically connected to the collector of the fourth phase-shifted full-bridge main arm switch, and the other end of the fourth parasitic capacitor is electrically connected to the emitter of the fourth phase-shifted full-bridge main arm switch. The emitter of the second phase-shifted full-bridge main arm switch is electrically connected to the opposite-name terminal of the first winding of the high-frequency transformer. The emitter of the second phase-shifted full-bridge main arm switch is electrically connected to the input terminal of the variable inductor unit. The control terminals of the second phase-shifted full-bridge main arm switch and the fourth phase-shifted full-bridge main arm switch are electrically connected to the output terminal of the controller.

[0014] Preferably, the frequency conversion unit includes a first bidirectional switching component and a second bidirectional switching component. The input terminal of the first bidirectional switching component is electrically connected to the same-name terminal of the second winding of the high-frequency transformer, the output terminal of the first bidirectional switching component is electrically connected to the input terminal of the filtering unit, the input terminal of the second bidirectional switching component is electrically connected to the opposite-name terminal of the third winding of the high-frequency transformer, the output terminal of the second bidirectional switching component is electrically connected to the input terminal of the filtering unit, and the control terminals of the first bidirectional switching component and the second bidirectional switching component are electrically connected to the output terminal of the controller.

[0015] Preferably, the first bidirectional switch assembly includes a first bidirectional switch, a first diode, a second diode, a third diode, and a fourth diode;

[0016] In this configuration, the anode of the first diode is electrically connected to the corresponding terminal of the second winding of the high-frequency transformer; the cathode of the first diode is electrically connected to the collector of the first bidirectional switch; the cathode of the second diode is electrically connected to the collector of the first bidirectional switch; the anode of the second diode is electrically connected to the cathode of the fourth diode; the cathode of the fourth diode is electrically connected to the input terminal of the filter unit; the anode of the fourth diode is electrically connected to the emitter of the first bidirectional switch; the emitter of the first bidirectional switch is electrically connected to the anode of the third diode; the cathode of the third diode is electrically connected to the corresponding terminal of the second winding of the high-frequency transformer; and the control terminal of the first bidirectional switch is electrically connected to the output terminal of the controller.

[0017] Preferably, the second bidirectional switching assembly includes a second bidirectional switch, a fifth diode, a sixth diode, a seventh diode, and an eighth diode;

[0018] Specifically, the anode of the fifth diode is electrically connected to the opposite-name terminal of the third winding of the high-frequency transformer; the cathode of the fifth diode is electrically connected to the collector of the second bidirectional switch; the cathode of the sixth diode is electrically connected to the collector of the second bidirectional switch; the anode of the sixth diode is electrically connected to the input terminal of the filter unit; the anode of the sixth diode is electrically connected to the cathode of the eighth diode; the anode of the eighth diode is electrically connected to the emitter of the second bidirectional switch; the emitter of the second bidirectional switch is electrically connected to the anode of the seventh diode; the cathode of the seventh diode is electrically connected to the opposite-name terminal of the third winding of the high-frequency transformer; and the control terminal of the second bidirectional switch is electrically connected to the output terminal of the controller.

[0019] Preferably, the filtering unit includes a filtering inductor and a filtering capacitor. One end of the filtering inductor is electrically connected to the positive terminal of the sixth diode, and the other end of the filtering inductor is electrically connected to one end of the filtering capacitor. The other end of the filtering capacitor is electrically connected to the opposite terminal of the second winding of the high-frequency transformer.

[0020] Preferably, the variable inductor unit includes a leakage inductor, a magnetizing inductor, a dual-winding high-frequency transformer, a switching transistor, a ninth diode, a tenth diode, an eleventh diode, and a twelfth diode;

[0021] In this configuration, one end of the leakage inductor is electrically connected to the emitter of the second phase-shifted full-bridge main arm switch; the other end of the leakage inductor is electrically connected to one end of the magnetizing inductor; the other end of the leakage inductor is electrically connected to the same-name terminal of the first winding of the dual-winding high-frequency transformer; the other end of the magnetizing inductor is electrically connected to the emitter of the first phase-shifted full-bridge main arm switch; the other end of the magnetizing inductor is electrically connected to the opposite-name terminal of the first winding of the dual-winding high-frequency transformer; the anode of the ninth diode is electrically connected to the same-name terminal of the second winding of the dual-winding high-frequency transformer; and the cathode of the ninth diode is electrically connected to the switch. The collector of the switching transistor is electrically connected; the cathode of the tenth diode is electrically connected to the collector of the switching transistor; the anode of the tenth diode is electrically connected to the cathode of the twelfth diode; the cathode of the twelfth diode is electrically connected to the opposite-name terminal of the second winding of the dual-winding high-frequency transformer; the anode of the twelfth diode is electrically connected to the emitter of the switching transistor; the emitter of the switching transistor is electrically connected to the anode of the eleventh diode; the cathode of the eleventh diode is electrically connected to the same-name terminal of the second winding of the dual-winding high-frequency transformer; and the control terminal of the switching transistor is electrically connected to the output terminal of the controller.

[0022] The present invention also provides a soft-switching device for a single-phase sinusoidal inverter based on a controllable inductor, including a controller and a soft-switching circuit for a single-phase sinusoidal inverter based on a controllable inductor as described in any of the above. The output terminal of the controller is electrically connected to the control terminal of the phase-shifting full-bridge converter unit, the control terminal of the frequency converter unit, and the control terminal of the variable inductor unit.

[0023] In summary, this embodiment provides a soft-switching circuit and device for a single-phase sinusoidal inverter based on a controllable inductor. By controlling the phase-shifting full-bridge converter unit to control the variable inductor unit as an equivalent controllable current source, the injected current is adjusted according to the load size, so that the switching transistors in the full-bridge circuit maintain a wide range of zero-voltage soft-switching operation during sinusoidal inversion. This achieves high-frequency, high-efficiency sinusoidal inversion, thereby solving the problem that in existing high-frequency chain inverters, the leading and lagging arms alternate once within one cycle of conversion, making it difficult for each switching transistor in the phase-shifting full-bridge converter to achieve soft switching for most of the operating time. Attached Figure Description

[0024] Figure 1 This is a circuit diagram illustrating a method for widening the soft-switching range of the hysteresis arm in a DC / DC phase-shifted full-bridge circuit.

[0025] Figure 2 This is a circuit diagram of a soft-switching circuit and device for a single-phase sinusoidal inverter based on a controllable inductor, provided in an embodiment of the present invention.

[0026] Figure 3 This is a circuit diagram of the variable inductor unit of a single-phase sinusoidal inverter soft-switching circuit and device based on a controllable inductor provided in an embodiment of the present invention.

[0027] Figure 4 This is an equivalent circuit diagram of the soft-switching circuit and device for a single-phase sinusoidal inverter based on a controllable inductor provided in an embodiment of the present invention.

[0028] Figure 5 This is a waveform diagram of the positive half-cycle operating mode of the soft-switching circuit and device for a single-phase sinusoidal inverter based on a controllable inductor provided in an embodiment of the present invention.

[0029] Figure 6 is an equivalent circuit diagram of each stage of the positive half-cycle operating mode of the soft-switching circuit and device of the single-phase sinusoidal inverter based on controllable inductor provided in the embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] Please see Figure 2 The first embodiment of the present invention provides a soft-switching circuit for a single-phase sinusoidal inverter based on a controllable inductor, including a phase-shifting full-bridge converter unit 1, a variable inductor unit 2, a high-frequency transformer T1, a frequency conversion unit 3, and a filter unit 4.

[0033] Specifically, the output terminal of the phase-shifting full-bridge converter unit 1 is electrically connected to the input terminal of the variable inductor unit 2, the output terminal of the phase-shifting full-bridge converter unit 1 is electrically connected to the primary winding of the high-frequency transformer T1, the secondary winding of the high-frequency transformer T1 is electrically connected to the input terminal of the frequency conversion unit 3, the input terminal of the filter unit 4 is electrically connected to the output terminal of the frequency conversion unit 3, and the output terminal of the filter unit 4 is electrically connected to the secondary winding of the high-frequency transformer T1.

[0034] The control terminals of the phase-shifting full-bridge converter 1, the frequency converter 3, and the variable inductor unit 2 are electrically connected to the output terminal of the controller.

[0035] Specifically, in this embodiment, the phase-shifting full-bridge converter 1 controls the variable inductor unit 2 to be equivalent to a controllable current source. The injected current is adjusted according to the load size, so that the switching transistors in the full-bridge circuit maintain zero-voltage soft-switching operation during the sinusoidal inversion process, especially near the zero-crossing point of the sinusoidal AC current, thereby achieving high-frequency and high-efficiency sinusoidal inversion.

[0036] In one possible embodiment of the present invention, the phase-shifting full-bridge converter 1 includes a DC voltage source Udc, a first bridge arm, and a second bridge arm. The first bridge arm is located on both sides of the DC voltage source Udc, and the second bridge arm is located on both sides of the first bridge arm. The center of the first bridge arm is electrically connected to the same-name terminal of the first winding of the high-frequency transformer T1, and the center of the second bridge arm is electrically connected to the opposite-name terminal of the first winding of the high-frequency transformer T1. The center of the first bridge arm and the center of the second bridge arm are electrically connected to the input terminal of the variable inductor unit 2, and the control terminals of the first bridge arm and the second bridge arm are electrically connected to the output terminal of the controller.

[0037] Specifically, in this embodiment, the first bridge arm includes a first phase-shifted full-bridge main bridge arm switch Q1, a first parasitic capacitance C1, a third phase-shifted full-bridge main bridge arm switch Q3, and a third parasitic capacitance C3; wherein, the positive terminal of the DC voltage source Udc is electrically connected to the collector of the first phase-shifted full-bridge main bridge arm switch Q1, the emitter of the first phase-shifted full-bridge main bridge arm switch Q1 is electrically connected to the collector of the third phase-shifted full-bridge main bridge arm switch Q3, and the emitter of the third phase-shifted full-bridge main bridge arm switch Q3 is electrically connected to the negative terminal of the DC voltage source Udc, and the first parasitic capacitance C1... One end of the first parasitic capacitor C1 is electrically connected to the collector of the first phase-shifted full-bridge main arm switch Q1, and the other end of the first parasitic capacitor C1 is electrically connected to the emitter of the first phase-shifted full-bridge main arm switch Q1. One end of the third parasitic capacitor C3 is electrically connected to the collector of the third phase-shifted full-bridge main arm switch Q3, and the other end of the third parasitic capacitor C3 is electrically connected to the emitter of the third phase-shifted full-bridge main arm switch Q3. The emitter of the first phase-shifted full-bridge main arm switch Q1 is electrically connected to the same-name terminal of the first winding of the high-frequency transformer T1. The emitter of the first phase-shifted full-bridge main arm switch Q1 is electrically connected to the input terminal of the variable inductor unit 2. The control terminals of the first phase-shifted full-bridge main arm switch Q1 and the third phase-shifted full-bridge main arm switch Q3 are electrically connected to the output terminal of the controller. The second bridge arm includes a second phase-shifted full-bridge main bridge arm switch Q2, a fourth phase-shifted full-bridge main bridge arm switch Q4, a second parasitic capacitor C2, and a fourth parasitic capacitor C4; wherein, the positive terminal of the DC voltage source Udc is electrically connected to the collector of the second phase-shifted full-bridge main bridge arm switch Q2, the emitter of the second phase-shifted full-bridge main bridge arm switch Q2 is electrically connected to the collector of the fourth phase-shifted full-bridge main bridge arm switch Q4, the emitter of the fourth phase-shifted full-bridge main bridge arm switch Q4 is electrically connected to the negative terminal of the DC voltage source Udc, one end of the second parasitic capacitor C2 is electrically connected to the collector of the second phase-shifted full-bridge main bridge arm switch Q2, the other end of the second parasitic capacitor C2 is electrically connected to the emitter of the second phase-shifted full-bridge main bridge arm switch Q4, and one end of the fourth parasitic capacitor C4 is electrically connected to the collector of the fourth phase-shifted full-bridge main bridge arm switch Q2. The collector of the main bridge arm switch Q4 is electrically connected, the other end of the fourth parasitic capacitor C4 is electrically connected to the emitter of the fourth phase-shifted full-bridge main bridge arm switch Q4, the emitter of the second phase-shifted full-bridge main bridge arm switch Q2 is electrically connected to the opposite-named terminal of the first winding of the high-frequency transformer T1, the emitter of the second phase-shifted full-bridge main bridge arm switch Q2 is electrically connected to the input terminal of the variable inductor unit 2, and the control terminals of the second phase-shifted full-bridge main bridge arm switch Q2 and the fourth phase-shifted full-bridge main bridge arm switch Q4 are electrically connected to the output terminal of the controller.

[0038] In this embodiment, the frequency conversion unit 3 includes a first bidirectional switching component and a second bidirectional switching component. The input terminal of the first bidirectional switching component is electrically connected to the same-name terminal of the second winding of the high-frequency transformer T1, the output terminal of the first bidirectional switching component is electrically connected to the input terminal of the filter unit 4, the input terminal of the second bidirectional switching component is electrically connected to the opposite-name terminal of the third winding of the high-frequency transformer T1, the output terminal of the second bidirectional switching component is electrically connected to the input terminal of the filter unit 4, and the control terminals of the first bidirectional switching component and the second bidirectional switching component are electrically connected to the output terminal of the controller. The first bidirectional switch assembly includes a first bidirectional switch Q5, a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The anode of the first diode D1 is electrically connected to the corresponding terminal of the second winding of the high-frequency transformer T1, and the cathode of the first diode D1 is electrically connected to the collector of the first bidirectional switch Q5. The cathode of the second diode D2 is electrically connected to the collector of the first bidirectional switch Q5, and the anode of the second diode D2 is electrically connected to the cathode of the fourth diode D4. The cathode of the fourth diode D4 is electrically connected to the input terminal of the filter unit 4, and the anode of the fourth diode D4 is electrically connected to the emitter of the first bidirectional switch Q5. The emitter of the first bidirectional switch Q5 is electrically connected to the anode of the third diode D3, and the cathode of the third diode D3 is electrically connected to the corresponding terminal of the second winding of the high-frequency transformer T1. The control terminal of the first bidirectional switch Q5 is electrically connected to the output terminal of the controller. The second bidirectional switch assembly includes a second bidirectional switch Q6, a fifth diode D5, a sixth diode D6, a seventh diode D7, and an eighth diode D8. The anode of the fifth diode D5 is electrically connected to the opposite-named terminal of the third winding of the high-frequency transformer T1; the cathode of the fifth diode D5 is electrically connected to the collector of the second bidirectional switch Q6; the cathode of the sixth diode D6 is electrically connected to the collector of the second bidirectional switch Q6; the anode of the sixth diode D6 is electrically connected to the input terminal of the filter unit 4; the anode of the sixth diode D4 is electrically connected to the cathode of the eighth diode D8; the anode of the eighth diode D8 is electrically connected to the emitter of the second bidirectional switch Q6; the emitter of the second bidirectional switch Q6 is electrically connected to the anode of the seventh diode D7; the cathode of the seventh diode D7 is electrically connected to the opposite-named terminal of the third winding of the high-frequency transformer T1; and the control terminal of the second bidirectional switch Q6 is electrically connected to the output terminal of the controller.

[0039] In this embodiment, the filtering unit 4 includes a filtering inductor LF and a filtering capacitor CF. One end of the filtering inductor LF is electrically connected to the positive terminal of the sixth diode D6, and the other end of the filtering inductor LF is electrically connected to one end of the filtering capacitor CF. The other end of the filtering capacitor CF is electrically connected to the opposite-name terminal of the second winding of the high-frequency transformer T1.

[0040] Please see Figure 3 In one possible embodiment of the present invention, the variable inductor unit 2 includes a leakage inductance LK1, a magnetizing inductance Lm, a dual-winding high-frequency transformer T2, a switching transistor Q7, a ninth diode SD3, a tenth diode SD4, an eleventh diode SD1, and a twelfth diode SD2; wherein, one end of the leakage inductance LK1 is electrically connected to the emitter of the second phase-shifted full-bridge main arm switch Q2, the other end of the leakage inductance LK1 is electrically connected to one end of the magnetizing inductance Lm, the other end of the leakage inductance LK1 is electrically connected to the same-name terminal of the first winding of the dual-winding high-frequency transformer T2, and the other end of the magnetizing inductance Lm is electrically connected to the emitter of the first phase-shifted full-bridge main arm switch Q1. The other end of the magnetizing inductor Lm is electrically connected to the opposite-named terminal of the first winding of the dual-winding high-frequency transformer T2. The anode of the ninth diode SD3 is electrically connected to the same-named terminal of the second winding of the dual-winding high-frequency transformer T2. The cathode of the ninth diode SD3 is electrically connected to the collector of the switching transistor Q7. The cathode of the tenth diode SD4 is electrically connected to the collector of the switching transistor Q7. The anode of the tenth diode SD4 is electrically connected to the cathode of the twelfth diode SD2. The cathode of the twelfth diode SD2 is electrically connected to the opposite-named terminal of the second winding of the dual-winding high-frequency transformer T2. The anode of the twelfth diode SD2 is electrically connected to the emitter of the switching transistor Q7. The emitter of the switching transistor Q7 is electrically connected to the anode of the eleventh diode SD1. The cathode of the eleventh diode SD1 is electrically connected to the same-named terminal of the second winding of the dual-winding high-frequency transformer T2. The control terminal of the switching transistor Q7 is electrically connected to the output terminal of the controller.

[0041] Specifically, in this embodiment, LK1 is the leakage inductance of the primary side of the dual-winding high-frequency transformer T2. When the switch Q7 is off, the secondary side of the dual-winding high-frequency transformer T2 is open-circuited, and the variable inductance Lin = LK1 + Lm. When the switch Q7 is on, the secondary side of the dual-winding high-frequency transformer T2 is short-circuited, and the variable inductance Lin = LK1. The period of the switch Q7 is set to TS, and the on-time within one period is DTS, where D is the duty cycle. Therefore, a controllable variable inductance Lin = LK1 + (1-D)Lm can be obtained within one switching cycle.

[0042] Please see Figure 4 As shown in Figure 6, in this embodiment, for ease of analysis of the soft-switching working principle, the variable inductor unit is equivalent to a controllable current source Isource. The magnitude of this current source can be controlled by controlling the switching transistor and thus adjusting the magnitude of the variable inductor. When the inverter output voltage is in the positive half-cycle mode, the first phase-shifted full-bridge main bridge arm switch Q1 and the third phase-shifted full-bridge main bridge arm switch Q3 are leading arms, and the second phase-shifted full-bridge main bridge arm switch Q2 and the fourth phase-shifted full-bridge main bridge arm switch Q4 are lagging arms; wherein, q1, q2, q3, and q4 are the driving signals of the first phase-shifted full-bridge main bridge arm switch Q1, the second phase-shifted full-bridge main bridge arm switch Q2, the third phase-shifted full-bridge main bridge arm switch Q3, and the fourth phase-shifted full-bridge main bridge arm switch Q4, respectively; Vds1, Vds2, Vds3, and Vds4 are the first phase-shifted full-bridge main bridge arm... The parasitic capacitance voltages of switch Q1, the second phase-shifted full-bridge main arm switch Q2, the third phase-shifted full-bridge main arm switch Q3, and the fourth phase-shifted full-bridge main arm switch Q4 are respectively; Ids1, Ids2, Ids3, and Ids4 are the parasitic capacitance currents of the first phase-shifted full-bridge main arm switch Q1, the second phase-shifted full-bridge main arm switch Q2, the third phase-shifted full-bridge main arm switch Q3, and the fourth phase-shifted full-bridge main arm switch Q4; Ipp is the primary current of the high-frequency transformer T1; Isource is the output current of the variable inductor unit 2; and Iload is the load current.

[0043] In stage 1 [t0, t1], the equivalent circuit is shown in Figure 6(a). During this stage, the second phase-shifted full-bridge main arm switch Q2 and the fourth phase-shifted full-bridge main arm switch Q4 are both in a dead-time state and not conducting. The third phase-shifted full-bridge main arm switch Q3 is conducting, the first phase-shifted full-bridge main arm switch Q1 is turning off, the second bidirectional switch Q6 is conducting, and the first bidirectional switch Q5 is turning off. The second phase-shifted full-bridge main arm switch Q2 completes zero-voltage soft-switching within the dead time. The primary current Ipp of the high-frequency transformer T1 and the output current Isource of the variable inductor unit 2 charge the fourth parasitic capacitor C4 and discharge the second parasitic capacitor C2. Before the second phase-shifted full-bridge main arm switch Q2 turns on, the parasitic capacitor charge is released to achieve soft switching. In the positive half-cycle mode, the second phase-shifted full-bridge main arm switch Q2 and the fourth phase-shifted full-bridge main arm switch Q4 are lagging arms and are difficult to achieve soft switching. Therefore, the size of the variable inductor unit 2 can be adjusted in this stage to control the output current Isource of the variable inductor unit 2. The output current Isource of the variable inductor unit 2 helps the lagging arm to achieve soft switching.

[0044] Stage 2 [t2, t3]: The equivalent circuit is shown in Figure 6(b). In this stage, the first phase-shifted full-bridge main arm switch Q1 and the third phase-shifted full-bridge main arm switch Q3 are both in dead-time and not conducting. The second phase-shifted full-bridge main arm switch Q2 is conducting, the fourth phase-shifted full-bridge main arm switch Q4 is turning off, the second bidirectional switch Q6 is conducting, and the first bidirectional switch Q5 is turning off. The first phase-shifted full-bridge main arm switch Q1 completes zero-voltage soft-switching within the dead time. The primary current Ipp of the high-frequency transformer T1 and the output current Isource of the variable inductor unit 2 charge the third parasitic capacitor C3 and discharge the first parasitic capacitor C1. Before the first phase-shifted full-bridge main arm switch Q1 is turned on, its parasitic capacitor charge is released to achieve soft switching. In the positive half-cycle mode, the first phase-shifted full-bridge main arm switch Q1 and the third phase-shifted full-bridge main arm switch Q3 are leading arms, so soft switching is easily achieved.

[0045] Stage 3 [t4, t5]: The equivalent circuit is shown in Figure 6(c). In this stage, the second phase-shifted full-bridge main arm switch Q2 and the fourth phase-shifted full-bridge main arm switch Q4 are both in dead-time and not conducting. The first phase-shifted full-bridge main arm switch Q1 is conducting, the third phase-shifted full-bridge main arm switch Q3 is turning off, the first bidirectional switch Q5 is conducting, the second bidirectional switch Q6 is turning off, and the fourth phase-shifted full-bridge main arm switch Q4 completes zero-voltage soft-switching within the dead time. The primary current Ipp of the high-frequency transformer T1 and the output current Isource of the variable inductor unit 2 charge the second parasitic capacitor C2 and discharge the fourth parasitic capacitor C4. Before the fourth phase-shifted full-bridge main arm switch Q4 is turned on, its parasitic capacitor charge is released to achieve soft switching. In the positive half-cycle mode, the second phase-shifted full-bridge main arm switch Q2 and the fourth phase-shifted full-bridge main arm switch Q4 are lagging arms and are difficult to achieve soft switching. Therefore, the size of the variable inductor unit 2 can be adjusted in this stage to control the output current Isource of the variable inductor unit 2. The output current Isource of the variable inductor unit 2 helps the lagging arm to achieve soft switching.

[0046] Stage 4 [t6, t7]: The equivalent circuit is shown in Figure 6(d). In this stage, the first phase-shifted full-bridge main arm switch Q1 and the third phase-shifted full-bridge main arm switch Q3 are both in dead-time and not conducting. The fourth phase-shifted full-bridge main arm switch Q4 is conducting, the second phase-shifted full-bridge main arm switch Q2 is turning off, the first bidirectional switch Q5 is conducting, the second bidirectional switch Q6 is turning off, and the third phase-shifted full-bridge main arm switch Q3 completes zero-voltage soft-switching within the dead time. The primary current Ipp of the high-frequency transformer T1 and the output current Isource of the variable inductor unit 2 charge the first parasitic capacitor C1 and discharge the third parasitic capacitor C3. Before the third phase-shifted full-bridge main arm switch Q3 is turned on, its parasitic capacitor charge is released to achieve soft switching. In the positive half-cycle mode, the first phase-shifted full-bridge main arm switch Q1 and the third phase-shifted full-bridge main arm switch Q3 are leading arms, so soft switching is easily achieved.

[0047] In this embodiment, when the inverter output voltage is in the negative half-cycle mode, the first phase-shifted full-bridge main bridge arm switch Q1 and the third phase-shifted full-bridge main bridge arm switch Q3 are lagging arms, and the second phase-shifted full-bridge main bridge arm switch Q2 and the fourth phase-shifted full-bridge main bridge arm switch Q4 are leading arms. Their soft-switching principle is the same as that of the aforementioned soft-switching principle in the positive half-cycle mode.

[0048] The present invention also provides a soft-switching device for a single-phase sinusoidal inverter based on a controllable inductor, including a controller and a soft-switching circuit for a single-phase sinusoidal inverter based on a controllable inductor as described in any of the above. The output terminal of the controller is electrically connected to the control terminal of the phase-shifting full-bridge converter 1, the control terminal of the frequency converter 3, and the control terminal of the variable inductor unit 2.

[0049] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention.

Claims

1. A single phase sinusoidal inverter soft switching circuit based on controllable inductance, characterized by, It includes a phase-shifting full-bridge converter unit, a variable inductor unit, a high-frequency transformer, a frequency converter unit, and a filter unit; Specifically, the output terminal of the phase-shifted full-bridge converter is electrically connected to the input terminal of the variable inductor unit, the output terminal of the phase-shifted full-bridge converter is electrically connected to the primary winding of the high-frequency transformer, the secondary winding of the high-frequency transformer is electrically connected to the input terminal of the frequency converter, the input terminal of the filter unit is electrically connected to the output terminal of the frequency converter, and the output terminal of the filter unit is electrically connected to the secondary winding of the high-frequency transformer. The control terminals of the phase-shifting full-bridge converter, the frequency converter, and the variable inductor unit are electrically connected to the output terminal of the controller. The phase-shifting full-bridge converter unit includes a DC voltage source, a first bridge arm, and a second bridge arm. The first bridge arm is located on both sides of the DC voltage source, and the second bridge arm is located on both sides of the first bridge arm. The center of the first bridge arm is electrically connected to the same-name terminal of the first winding of the high-frequency transformer, and the center of the second bridge arm is electrically connected to the opposite-name terminal of the first winding of the high-frequency transformer. The center of the first bridge arm and the center of the second bridge arm are electrically connected to the input terminal of the variable inductor unit. The control terminals of the first bridge arm and the second bridge arm are electrically connected to the output terminal of the controller.

2. The soft-switching circuit for a single-phase sinusoidal inverter based on a controllable inductor according to claim 1, characterized in that, The first bridge arm includes a first phase-shifted full-bridge main bridge arm switch, a first parasitic capacitor, a third phase-shifted full-bridge main bridge arm switch, and a third parasitic capacitor; Wherein, the positive terminal of the DC voltage source is electrically connected to the collector of the first phase-shifted full-bridge main arm switch, the emitter of the first phase-shifted full-bridge main arm switch is electrically connected to the collector of the third phase-shifted full-bridge main arm switch, the emitter of the third phase-shifted full-bridge main arm switch is electrically connected to the negative terminal of the DC voltage source, one end of the first parasitic capacitor is electrically connected to the collector of the first phase-shifted full-bridge main arm switch, and the other end of the first parasitic capacitor is electrically connected to the emitter of the first phase-shifted full-bridge main arm switch, and the third parasitic capacitor... One end of the third parasitic capacitor is electrically connected to the collector of the third phase-shifted full-bridge main arm switch, and the other end of the third parasitic capacitor is electrically connected to the emitter of the third phase-shifted full-bridge main arm switch. The emitter of the first phase-shifted full-bridge main arm switch is electrically connected to the same-name terminal of the first winding of the high-frequency transformer. The emitter of the first phase-shifted full-bridge main arm switch is electrically connected to the input terminal of the variable inductor unit. The control terminals of the first phase-shifted full-bridge main arm switch and the third phase-shifted full-bridge main arm switch are electrically connected to the output terminal of the controller.

3. The controllable inductance based single phase sine wave inverter soft switching circuit of claim 2, wherein, The second bridge arm includes a second phase-shifted full-bridge main bridge arm switch, a fourth phase-shifted full-bridge main bridge arm switch, a second parasitic capacitor, and a fourth parasitic capacitor; Wherein, the positive terminal of the DC voltage source is electrically connected to the collector of the second phase-shifted full-bridge main arm switch, the emitter of the second phase-shifted full-bridge main arm switch is electrically connected to the collector of the fourth phase-shifted full-bridge main arm switch, the emitter of the fourth phase-shifted full-bridge main arm switch is electrically connected to the negative terminal of the DC voltage source, one end of the second parasitic capacitor is electrically connected to the collector of the second phase-shifted full-bridge main arm switch, and the other end of the second parasitic capacitor is electrically connected to the emitter of the second phase-shifted full-bridge main arm switch, and the fourth parasitic capacitor... One end of the fourth parasitic capacitor is electrically connected to the collector of the fourth phase-shifted full-bridge main arm switch, and the other end of the fourth parasitic capacitor is electrically connected to the emitter of the fourth phase-shifted full-bridge main arm switch. The emitter of the second phase-shifted full-bridge main arm switch is electrically connected to the opposite-named terminal of the first winding of the high-frequency transformer. The emitter of the second phase-shifted full-bridge main arm switch is electrically connected to the input terminal of the variable inductor unit. The control terminals of the second phase-shifted full-bridge main arm switch and the fourth phase-shifted full-bridge main arm switch are electrically connected to the output terminal of the controller.

4. The controllable inductance based single phase sine wave inverter soft switching circuit of claim 1, wherein, The frequency conversion unit includes a first bidirectional switching component and a second bidirectional switching component. The input terminal of the first bidirectional switching component is electrically connected to the same-name terminal of the second winding of the high-frequency transformer. The output terminal of the first bidirectional switching component is electrically connected to the input terminal of the filter unit. The input terminal of the second bidirectional switching component is electrically connected to the opposite-name terminal of the third winding of the high-frequency transformer. The output terminal of the second bidirectional switching component is electrically connected to the input terminal of the filter unit. The control terminals of the first bidirectional switching component and the second bidirectional switching component are electrically connected to the output terminal of the controller.

5. The controllable inductance based single phase sine wave inverter soft switching circuit of claim 4, wherein, The first bidirectional switching assembly includes a first bidirectional switch, a first diode, a second diode, a third diode, and a fourth diode; In this configuration, the anode of the first diode is electrically connected to the corresponding terminal of the second winding of the high-frequency transformer; the cathode of the first diode is electrically connected to the collector of the first bidirectional switch; the cathode of the second diode is electrically connected to the collector of the first bidirectional switch; the anode of the second diode is electrically connected to the cathode of the fourth diode; the cathode of the fourth diode is electrically connected to the input terminal of the filter unit; the anode of the fourth diode is electrically connected to the emitter of the first bidirectional switch; the emitter of the first bidirectional switch is electrically connected to the anode of the third diode; the cathode of the third diode is electrically connected to the corresponding terminal of the second winding of the high-frequency transformer; and the control terminal of the first bidirectional switch is electrically connected to the output terminal of the controller.

6. The controllable inductance based single phase sine wave inverter soft switching circuit of claim 4, wherein, The second bidirectional switching assembly includes a second bidirectional switch, a fifth diode, a sixth diode, a seventh diode, and an eighth diode; Specifically, the anode of the fifth diode is electrically connected to the opposite-name terminal of the third winding of the high-frequency transformer; the cathode of the fifth diode is electrically connected to the collector of the second bidirectional switch; the cathode of the sixth diode is electrically connected to the collector of the second bidirectional switch; the anode of the sixth diode is electrically connected to the input terminal of the filter unit; the anode of the sixth diode is electrically connected to the cathode of the eighth diode; the anode of the eighth diode is electrically connected to the emitter of the second bidirectional switch; the emitter of the second bidirectional switch is electrically connected to the anode of the seventh diode; the cathode of the seventh diode is electrically connected to the opposite-name terminal of the third winding of the high-frequency transformer; and the control terminal of the second bidirectional switch is electrically connected to the output terminal of the controller.

7. The controllable inductance based single phase sine wave inverter soft switching circuit of claim 6, wherein, The filtering unit includes a filtering inductor and a filtering capacitor. One end of the filtering inductor is electrically connected to the positive terminal of the sixth diode, and the other end of the filtering inductor is electrically connected to one end of the filtering capacitor. The other end of the filtering capacitor is electrically connected to the opposite terminal of the second winding of the high-frequency transformer.

8. The soft-switching circuit for a single-phase sinusoidal inverter based on a controllable inductor according to claim 3, characterized in that, The variable inductor unit includes a leakage inductor, a magnetizing inductor, a dual-winding high-frequency transformer, a switching transistor, a ninth diode, a tenth diode, an eleventh diode, and a twelfth diode; Wherein, one end of the leakage inductor is electrically connected to the emitter of the second phase-shifted full-bridge main arm switch; the other end of the leakage inductor is electrically connected to one end of the magnetizing inductor; the other end of the leakage inductor is electrically connected to the same-name terminal of the first winding of the dual-winding high-frequency transformer; the other end of the magnetizing inductor is electrically connected to the emitter of the first phase-shifted full-bridge main arm switch; the other end of the magnetizing inductor is electrically connected to the opposite-name terminal of the first winding of the dual-winding high-frequency transformer; the anode of the ninth diode is electrically connected to the same-name terminal of the second winding of the dual-winding high-frequency transformer; and the cathode of the ninth diode is electrically connected to the... The collector of the switching transistor is electrically connected; the cathode of the tenth diode is electrically connected to the collector of the switching transistor; the anode of the tenth diode is electrically connected to the cathode of the twelfth diode; the cathode of the twelfth diode is electrically connected to the opposite-name terminal of the second winding of the dual-winding high-frequency transformer; the anode of the twelfth diode is electrically connected to the emitter of the switching transistor; the emitter of the switching transistor is electrically connected to the anode of the eleventh diode; the cathode of the eleventh diode is electrically connected to the same-name terminal of the second winding of the dual-winding high-frequency transformer; and the control terminal of the switching transistor is electrically connected to the output terminal of the controller.

9. A soft-switching device for a single-phase sinusoidal inverter based on a controllable inductor, characterized in that, The system includes a controller and a single-phase sinusoidal inverter soft-switching circuit based on a controllable inductor as described in any one of claims 1 to 8, wherein the output terminal of the controller is electrically connected to the control terminal of the phase-shifting full-bridge converter unit, the control terminal of the frequency converter unit, and the control terminal of the variable inductor unit.

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