A single-stage multi-port Buck-Boost inverter circuit and conversion method

Abstract

The present invention provides a single-stage multi-port Buck-Boost inverter circuit and a conversion method. By setting a first coupled inductor circuit and a second coupled inductor circuit with two different impedances, the problem of discontinuous output current in the prior art can be solved; a multi-input boost converter is adopted to solve the problem of unstable low DC voltage generated by the circuit in the prior art; a single-stage multi-port Buck-Boost inverter is used to reduce the number of active and passive components in the power conversion stage, and the number of semiconductors used is less than that in the prior art, thereby reducing cost, weight and volume; the solution in the present application does not use a larger electrolytic capacitor, and does not use a plurality of DC-DC converters in parallel, which can solve the problem of circulating current generated by a larger electrolytic capacitor or a parallel converter in the prior art; a smaller electrolytic capacitor is used in a targeted manner to improve the reliability of the system and the total power density of the system; and thus the present application can eliminate the problem of circulating current generated by inverter circuits in parallel.

Description

Technical Field

[0001] The present invention belongs to the technical field of microgrids, and in particular relates to a single-stage multi-port Buck-Boost inverter circuit and a conversion method. Background Art

[0002] Solar energy and wind energy are available everywhere on the earth and are renewable energy, so they have become the most attractive energy sources in the future. However, solar energy and wind energy are intermittent, and the reliability of supplying power to loads alone is low. In order to overcome this problem, the existing technology uses PV and FC systems together. During the day, photovoltaic panels mainly generate more energy and do not need fuel cells to supply power. At night, photovoltaic panels do not generate energy. At this time, FC systems can be used to supply power to loads; photovoltaic panels and ordinary batteries can also be used to form another hybrid renewable energy system. The principle at this time is the same as that of the FC system. However, the hybrid renewable energy system formed by photovoltaic panels and FC systems usually produces unstable and low DC voltages. In order to overcome this problem, the existing technology uses a boost multi-input inverter. In order to improve the performance and life of photovoltaic panels and FC, the converter used in the system should have a continuous output current.

[0003] The first problem of the DC-AC energy conversion structure in the prior art is that the parallel connection of the DC-DC converter will generate circulating current, which will cause adverse effects such as output current distortion, increased current stress of switching devices, increased power loss, and reduced system efficiency. In addition, from the perspective of electromagnetic interference, the high-frequency content in the circulating current may cause serious problems. The prior art can reduce the circulating current by adding additional controllers and sensors, but this will increase the complexity and cost of the system. The second problem of the DC-AC energy conversion structure in the prior art is that bulky electrolytic capacitors are required to handle the high ripple current on the tributary link. Since electrolytic capacitors have the characteristics of short life, fast performance degradation and usually require a large space, such a design increases the volume and weight of the design. These undesirable reasons reduce the reliability and total power density of the system and increase the total cost of the system. Technicians have begun to study new methods to reduce the capacitance of the DC link, thereby reducing the failure rate of the system and improving reliability.

[0004] At the same time, in order to stabilize the input voltage in the existing technology, many semiconductors need to be connected to the AC power grid. The risk of semiconductor short circuit increases the cost, weight, volume and complexity of the system. In addition, the topology of the dual inverter uses a low-frequency transformer and more switches, which is very costly and heavy. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a single-stage multi-port Buck-Boost inverter circuit and conversion method, which can eliminate the problem of circulating current generated by parallel inverter circuits, while reducing the volume and cost of the inverter circuit and extending the service life of the circuit.

[0006] The present invention is achieved through the following technical solutions:

[0007] A single-stage multi-port Buck-Boost inverter circuit, characterized in that it comprises a first coupled inductor circuit and a second coupled inductor circuit respectively connected to separate DC sources, wherein the second coupled inductor circuit is connected to a three-phase inverter unit and a filter;

[0008] The first coupled inductor circuit and the second coupled inductor circuit are inductively coupled to each other via a first coupled inductor, and the second coupled inductor circuit includes a second coupled inductor.

[0009] Further, the first coupled inductor includes an inductor N11, an inductor N12 and an inductor N13; the second coupled inductor includes an inductor N21, an inductor N22 and an inductor N23 connected in parallel;

[0010] The inductor N13 is located in the second coupled inductor circuit and is inductively coupled to the inductor N11 and the inductor N12.

[0011] Further, the turns ratio of the coupled inductors of the first coupled inductor and the second coupled inductor is:

[0012] a2=N12 / N11, a3=N13 / N11, a'2=N22 / N21, a'3=N23 / N21.

[0013] Further, the first coupled inductor circuit includes a DC source Vi1, the positive electrode of the DC source Vi1 is connected to one end of the inductor L1, the other end of the inductor L1 is respectively connected to the positive electrode of the capacitor C1 and the positive electrode of the diode D1, the negative electrode of the diode D1 is connected to one end of the inductor N12, the other end of the inductor N12 is respectively connected to the negative electrode of the capacitor C2, one end of the inductor N11 and one end of the inductor L3, the negative electrode of the capacitor C1 and the other end of the inductor L3 are sequentially connected to the inductor N11 and connected to the collector of the switch tube S1, and the emitter of the switch tube S1 is sequentially connected to the positive electrode of the capacitor C2 and the negative electrode of the DC source Vi1.

[0014] Further, the second coupled inductor circuit includes a DC source Vi2, the positive electrode of the DC source Vi2 is connected to one end of the inductor L2, the other end of the inductor L2 is respectively connected to the positive electrode of the capacitor C3 and the positive electrode of the diode D2, the negative electrode of the diode D2 is connected to one end of the inductor N23, the other end of the inductor N23 is respectively connected to one end of the inductor L4, one end of the inductor N21 and one end of the inductor N22, the other end of the inductor L4 is connected to one end of the inductor N13, the other end of the inductor N22 is connected to the negative electrode of the capacitor C4, and the other end of the inductor N22 is connected to the positive electrode of the capacitor C5;

[0015] The cathode of the capacitor C3 is connected to the connection line between the inductor L4 and the inductor N13 and the connection line between the inductor N21 and the capacitor C5 in sequence; the other end of the inductor N13 is connected to the anode of the diode D3;

[0016] The cathode of the diode D3 and the cathode of the capacitor C5 are connected and connected to one end of the three-phase inverter unit, and the other end of the three-phase inverter unit is connected to the anode of the capacitor C4 and the cathode of the DC source Vi2 respectively.

[0017] Furthermore, the capacitor C1, the capacitor C2, the capacitor C3, the capacitor C4 and the capacitor C5 are all electrolytic capacitors.

[0018] Further, the three-phase inverter unit includes a switch tube Si1, a switch tube Si2, a switch tube Si3, a switch tube Si4, a switch tube Si5 and a switch tube Si6;

[0019] The emitter of the switch tube Si1 is connected to the collector of the switch tube Si2, and a first phase output terminal is provided on the connection line between the switch tube Si1 and the switch tube Si2; the emitter of the switch tube Si3 is connected to the collector of the switch tube Si4, and a second phase output terminal is provided on the connection line between the switch tube Si3 and the switch tube Si4; the emitter of the switch tube Si5 is connected to the collector of the switch tube Si6, and a third phase output terminal is provided on the connection line between the switch tube Si5 and the switch tube Si6;

[0020] The cathode of the capacitor C5 is connected to the emitters of the switch tubes Si1, Si3 and Si5 respectively, and the anode of the capacitor C4 is connected to the emitters of the switch tubes Si2, Si4 and Si6 respectively;

[0021] The first phase output terminal, the second phase output terminal and the third phase output terminal are connected to the input terminal of the filter, and the output terminal of the filter is connected to a three-phase load.

[0022] Furthermore, the switch tube Si1 , the switch tube Si2 , the switch tube Si3 , the switch tube Si4 , the switch tube Si5 and the switch tube Si6 are all IGBT switch tubes.

[0023] A conversion method for a single-stage multi-port Buck-Boost inverter circuit comprises the following steps:

[0024] Mode 1: When the switch tube S1 is turned on and the three-phase inverter unit is short-circuited, the diode D3 and at least one bridge arm in the three-phase inverter unit are turned on; the diode D1 and the diode D2 are turned off;

[0025] Mode 2: When the switch tube S1 is turned on and the three-phase inverter unit is not short-circuited, the diodes D2 and D3 are turned on; the diode D1 is turned off;

[0026] Mode 3: When the switch tube S1 is disconnected and the three-phase inverter unit is short-circuited, the diode D1 and at least one bridge arm of the three-phase inverter unit are turned on; the diode D2 and the diode D3 are turned off;

[0027] Mode 4: When the switch tube S1 is disconnected and the three-phase inverter unit is not short-circuited, the diodes D1 and D2 are turned on; and the diode D3 is turned off.

[0028] Furthermore, it is characterized in that, if the switch tube S1 is turned on and the diode D1 is turned off, the inductor L1, the inductor L3 and the capacitor C5 start to charge, and the capacitors C1 and C2 start to discharge;

[0029] If the switch tube S1 is turned off and the diode D1 is turned on, the inductor L1, the inductor L3 and the capacitor C5 start to discharge, and the capacitors C1 and C2 start to charge.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] The present invention provides a single-stage multi-port Buck-Boost inverter circuit and a conversion method. By setting a first coupled inductor circuit and a second coupled inductor circuit with two different impedances, continuous current can be introduced from two output terminals, which can solve the problem of discontinuous output current in the prior art. The present application adopts two different impedance networks, namely, two port parts connected by a DC source Vi1 and a DC source Vi2 to form a multi-input boost converter, which can solve the problem of unstable low DC voltage generated by the circuit in the prior art. The use of a single-stage multi-port Buck-Boost inverter can reduce the number of active and passive components in the power conversion stage, and the use of The number of semiconductors is less than that in the prior art, thereby reducing cost, weight and volume; the solution in the present application does not use a larger electrolytic capacitor, and does not use multiple DC-DC converters in parallel, so it can solve the problem of circulating current generated by larger electrolytic capacitors or parallel converters in the prior art; since the bulky electrolytic capacitors have a short life, rapid performance degradation and usually require a larger space, the circuit topology of the present application uses smaller electrolytic capacitors to improve the reliability of the system and the total power density of the system to address this problem; and thus the present application can eliminate the problem of circulating current generated by parallel inverter circuits, while reducing the volume and cost of the inverter circuit and extending the service life of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A topological diagram of a single-stage multi-port Buck-Boost inverter circuit in a specific embodiment of the present invention;

[0033] Figure 2 It is a first working mode of a single-stage multi-port Buck-Boost inverter circuit in a specific embodiment of the present invention;

[0034] Figure 3 It is a second working mode of a single-stage multi-port Buck-Boost inverter circuit in a specific embodiment of the present invention;

[0035] Figure 4 It is the third working mode of a single-stage multi-port Buck-Boost inverter circuit in a specific embodiment of the present invention;

[0036] Figure 5 This is the fourth working mode of a single-stage multi-port Buck-Boost inverter circuit in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0038] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0040] The present invention provides a single-stage multi-port Buck-Boost inverter circuit, such as Figure 1 As shown, it includes a first coupled inductor circuit and a second coupled inductor circuit respectively connected to separate DC sources. Specifically, the DC source performs DC voltage conversion through two Buck-Boost DC conversion ports, and the DC conversion ports are the first coupled inductor circuit and the second coupled inductor circuit;

[0041] The second coupled inductor circuit is connected to a three-phase inverter unit and a filter; specifically, the filter is an Lc filter, and the present application converts the DC current into AC current through the three-phase inverter unit to complete the inversion;

[0042] The first coupled inductor circuit and the second coupled inductor circuit are inductively coupled to each other through a first coupled inductor, and the second coupled inductor circuit includes a second coupled inductor; specifically, Figure 1 As shown, the first coupled inductor is represented by an asterisk to indicate polarity, and the second coupled inductor is represented by a dot to indicate polarity.

[0043] A preferred embodiment provided by the present invention is that the first coupled inductor includes an inductor N11, an inductor N12 and an inductor N13; the second coupled inductor includes an inductor N21, an inductor N22 and an inductor N23 connected in parallel;

[0044] The inductor N13 is located in the second coupled inductor circuit and is inductively coupled to the inductor N11 and the inductor N12. Further, the turns ratio of the coupled inductors of the first coupled inductor and the second coupled inductor is:

[0045] a2=N12 / N11, a3=N13 / N11, a'2=N22 / N21, a'3=N23 / N21.

[0046] A preferred embodiment provided by the present invention is that the first coupled inductor circuit includes a DC source Vi1, the positive electrode of the DC source Vi1 is connected to one end of the inductor L1, the other end of the inductor L1 is respectively connected to the positive electrode of the capacitor C1 and the positive electrode of the diode D1, the negative electrode of the diode D1 is connected to one end of the inductor N12, the other end of the inductor N12 is respectively connected to the negative electrode of the capacitor C2, one end of the inductor N11 and one end of the inductor L3, the negative electrode of the capacitor C1 and the other end of the inductor L3 are sequentially connected to the inductor N11 and connected to the collector of the switch tube S1, and the emitter of the switch tube S1 is sequentially connected to the positive electrode of the capacitor C2 and the negative electrode of the DC source Vi1.

[0047] Specifically, the switching modes of the switch tube S1 and the three-phase inverter unit are independent.

[0048] A preferred embodiment provided by the present invention is that the second coupled inductor circuit includes a DC source Vi2, the positive electrode of the DC source Vi2 is connected to one end of the inductor L2, the other end of the inductor L2 is respectively connected to the positive electrode of the capacitor C3 and the positive electrode of the diode D2, the negative electrode of the diode D2 is connected to one end of the inductor N23, the other end of the inductor N23 is respectively connected to one end of the inductor L4, one end of the inductor N21 and one end of the inductor N22, the other end of the inductor L4 is connected to one end of the inductor N13, the other end of the inductor N22 is connected to the negative electrode of the capacitor C4, and the other end of the inductor N22 is connected to the positive electrode of the capacitor C5;

[0049] The cathode of the capacitor C3 is connected to the connection line between the inductor L4 and the inductor N13 and the connection line between the inductor N21 and the capacitor C5 in sequence; the other end of the inductor N13 is connected to the anode of the diode D3;

[0050] The cathode of the diode D3 and the cathode of the capacitor C5 are connected and connected to one end of the three-phase inverter unit, and the other end of the three-phase inverter unit is respectively connected to the anode of the capacitor C4 and the cathode of the DC source Vi2.

[0051] Specifically, although the two port parts connected to the DC source Vi1 and the DC source Vi2 are connected through the first coupling inductor, the two parts are independent of each other.

[0052] Furthermore, the capacitor C1, capacitor C2, capacitor C3, capacitor C4 and capacitor C5 are all electrolytic capacitors, which have large capacity and low price; specifically, the capacitor C1, capacitor C2, capacitor C3, capacitor C4 and capacitor C5 used in this application are all 470μf, the inductor L1 and inductor L3 are 240μH, and the inductor L2 and inductor L4 are 2940μH.

[0053] A preferred embodiment provided by the present invention is that the three-phase inverter unit includes a switch tube Si1, a switch tube Si2, a switch tube Si3, a switch tube Si4, a switch tube Si5 and a switch tube Si6;

[0054] The emitter of the switch tube Si1 is connected to the collector of the switch tube Si2, and a first phase output terminal is provided on the connection line between the switch tube Si1 and the switch tube Si2; the emitter of the switch tube Si3 is connected to the collector of the switch tube Si4, and a second phase output terminal is provided on the connection line between the switch tube Si3 and the switch tube Si4; the emitter of the switch tube Si5 is connected to the collector of the switch tube Si6, and a third phase output terminal is provided on the connection line between the switch tube Si5 and the switch tube Si6;

[0055] The cathode of the capacitor C5 is connected to the emitters of the switch tubes Si1, Si3 and Si5 respectively, and the anode of the capacitor C4 is connected to the emitters of the switch tubes Si2, Si4 and Si6 respectively;

[0056] The first phase output terminal, the second phase output terminal and the third phase output terminal are connected to the input terminal of the filter, and the output terminal of the filter is connected to a three-phase load.

[0057] Furthermore, the switch tube Si1, switch tube Si2, switch tube Si3, switch tube Si4, switch tube Si5 and switch tube Si6 all adopt IGBT switch tubes. This is because the maximum saturation current of the collector of the IGBT switch tube is large and the breakdown voltage is high. When the capacity of the inverter used as an inverter device reaches more than 250kVA, the operating frequency can reach 20kHz; specifically, the IGBT switch tube used in this application is selected as the IRFP460 model, with an operating voltage of 500V, an operating current of 20A, and an operating frequency of 10kHz.

[0058] The present invention provides a conversion method for a single-stage multi-port Buck-Boost inverter circuit, comprising the following steps:

[0059] Mode 1:

[0060] like Figure 2 As shown, when the switch tube S1 is turned on and the three-phase inverter unit is short-circuited, the diode D3 and at least one bridge arm in the three-phase inverter unit are turned on; the diode D1 and the diode D2 are turned off;

[0061] Mode 2:

[0062] like Figure 3 As shown, when the switch tube S1 is turned on and the three-phase inverter unit is not short-circuited, the diodes D2 and D3 are turned on; the diode D1 is turned off;

[0063] Mode 3:

[0064] like Figure 4 As shown, when the switch tube S1 is disconnected and the three-phase inverter unit is short-circuited, the diode D1 and at least one bridge arm of the three-phase inverter unit are turned on; the diode D2 and the diode D3 are turned off;

[0065] Mode 4:

[0066] like Figure 5 As shown, when the switch tube S1 is disconnected and the three-phase inverter unit is not short-circuited, the diode D1 and the diode D2 are turned on; and the diode D3 is turned off.

[0067] Furthermore, if the switch tube S1 is turned on and the diode D1 is turned off, the inductor L1, the inductor 3 and the capacitor C5 begin to charge, and the capacitors C1 and C2 begin to discharge;

[0068] If the switch tube S1 is turned off and the diode D1 is turned on, the inductor L1, the inductor 3 and the capacitor C5 start to discharge, and the capacitors C1 and C2 start to charge.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single-stage multi-port Buck-Boost inverter circuit, characterized in that: It comprises a first coupled inductor circuit and a second coupled inductor circuit respectively connected to separate direct current sources, wherein the second coupled inductor circuit is connected to a three-phase inverter unit and a filter; The first coupled inductor circuit and the second coupled inductor circuit are inductively coupled to each other via a first coupled inductor, and the second coupled inductor circuit includes a second coupled inductor; The first coupled inductor includes an inductor N11, an inductor N12 and an inductor N13; the second coupled inductor includes an inductor N21, an inductor N22 and an inductor N23 connected in parallel; The inductor N13 is located in the second coupled inductor circuit and is inductively coupled to the inductor N11 and the inductor N12; The first coupled inductor circuit includes a DC source Vi1, wherein the positive electrode of the DC source Vi1 is connected to one end of the inductor L1, and the other end of the inductor L1 is respectively connected to the positive electrode of the capacitor C1 and the positive electrode of the diode D1, the negative electrode of the diode D1 is connected to one end of the inductor N12, and the other end of the inductor N12 is respectively connected to the negative electrode of the capacitor C2, one end of the inductor N11 and one end of the inductor L3, the negative electrode of the capacitor C1 and the other end of the inductor L3 are sequentially connected to the inductor N11 and connected to the collector of the switch tube S1, and the emitter of the switch tube S1 is sequentially connected to the positive electrode of the capacitor C2 and the negative electrode of the DC source Vi1; The second coupled inductor circuit includes a DC source Vi2, a positive electrode of the DC source Vi2 is connected to one end of the inductor L2, the other end of the inductor L2 is respectively connected to the positive electrode of the capacitor C3 and the positive electrode of the diode D2, the negative electrode of the diode D2 is connected to one end of the inductor N23, the other end of the inductor N23 is respectively connected to one end of the inductor L4, one end of the inductor N21 and one end of the inductor N22, the other end of the inductor L4 is connected to one end of the inductor N13, the other end of the inductor N22 is connected to the negative electrode of the capacitor C4, and the other end of the inductor N22 is connected to the positive electrode of the capacitor C5; The cathode of the capacitor C3 is connected to the connection line between the inductor L4 and the inductor N13 and the connection line between the inductor N21 and the capacitor C5 in sequence; the other end of the inductor N13 is connected to the anode of the diode D3; The cathode of the diode D3 and the cathode of the capacitor C5 are connected and connected to one end of the three-phase inverter unit, and the other end of the three-phase inverter unit is connected to the anode of the capacitor C4 and the cathode of the DC source Vi2 respectively.

2. A single-stage multi-port Buck-Boost inverter circuit according to claim 1, characterized in that: The turns ratio of the first coupled inductor and the second coupled inductor is: a2=N12 / N11, a3=N13 / N11, a'2=N22 / N21, a'3=N23 / N21.

3. A single-stage multi-port Buck-Boost inverter circuit according to claim 1, characterized in that: The capacitor C1, the capacitor C2, the capacitor C3, the capacitor C4 and the capacitor C5 are all electrolytic capacitors.

4. A single-stage multi-port Buck-Boost inverter circuit according to claim 1, characterized in that: The three-phase inverter unit includes a switch tube Si1, a switch tube Si2, a switch tube Si3, a switch tube Si4, a switch tube Si5 and a switch tube Si6; The emitter of the switch tube Si1 is connected to the collector of the switch tube Si2, and a first phase output terminal is provided on the connection line between the switch tube Si1 and the switch tube Si2; the emitter of the switch tube Si3 is connected to the collector of the switch tube Si4, and a second phase output terminal is provided on the connection line between the switch tube Si3 and the switch tube Si4; the emitter of the switch tube Si5 is connected to the collector of the switch tube Si6, and a third phase output terminal is provided on the connection line between the switch tube Si5 and the switch tube Si6; The cathode of the capacitor C5 is connected to the emitters of the switch tubes Si1, Si3 and Si5 respectively, and the anode of the capacitor C4 is connected to the emitters of the switch tubes Si2, Si4 and Si6 respectively; The first phase output terminal, the second phase output terminal and the third phase output terminal are connected to the input terminal of the filter, and the output terminal of the filter is connected to a three-phase load.

5. A single-stage multi-port Buck-Boost inverter circuit according to claim 4, characterized in that: The switch tube Si1 , switch tube Si2 , switch tube Si3 , switch tube Si4 , switch tube Si5 and switch tube Si6 are all IGBT switch tubes.

6. A conversion method for a single-stage multi-port Buck-Boost inverter circuit, characterized in that: A single-stage multi-port Buck-Boost inverter circuit according to any one of claims 1 to 5, comprising the following steps: Mode 1: When the switch tube S1 is turned on and the three-phase inverter unit is short-circuited, the diode D3 and at least one bridge arm in the three-phase inverter unit are turned on; the diode D1 and the diode D2 are turned off; Mode 2: When the switch tube S1 is turned on and the three-phase inverter unit is not short-circuited, the diodes D2 and D3 are turned on; the diode D1 is turned off; Mode 3: When the switch tube S1 is disconnected and the three-phase inverter unit is short-circuited, the diode D1 and at least one bridge arm of the three-phase inverter unit are turned on; the diode D2 and the diode D3 are turned off; Mode 4: When the switch tube S1 is disconnected and the three-phase inverter unit is not short-circuited, the diodes D1 and D2 are turned on; and the diode D3 is turned off.

7. The conversion method of a single-stage multi-port Buck-Boost inverter circuit according to claim 6, characterized in that: If the switch tube S1 is turned on and the diode D1 is turned off, the inductor L1, the inductor L3 and the capacitor C5 start to charge, and the capacitors C1 and C2 start to discharge; If the switch tube S1 is turned off and the diode D1 is turned on, the inductor L1, the inductor L3 and the capacitor C5 start to discharge, and the capacitors C1 and C2 start to charge.

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