Single-stage isolation AC-DC converter with active clamping and system

Abstract

The invention discloses a single-stage isolation AC-DC converter with active clamping and a system. The converter comprises an AC end, an AC filter, a first rectification / inversion circuit, an active clamping circuit, a chopper circuit unit, a DC filter and a DC end which are connected in sequence. The chopper circuit unit comprises an inversion / rectification circuit, a transformer and a second rectification / inversion circuit which are connected in sequence; the inversion / rectification circuit is connected with the active clamping circuit, and the second rectification / inversion circuit is connected with the DC filter; the active clamping circuit is used for converting the alternating current signal output by the first rectification / inversion circuit into a PWM signal; the inversion / rectification circuit and the second rectification / inversion circuit are used for working in a square wave inversion state with a dead zone, converting voltage levels and realizing soft switching, a large-capacity bus capacitor is not needed, and the inverter has the characteristics of small switching loss, high efficiency, high power density, simple control method, small starting impact current, wide voltage range, long service life and the like.

Description

Technical Field

[0001] The invention relates to the technical field of power electronic conversion, and in particular to a single-stage isolated AC-DC converter with source clamping and a system thereof. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] In the electric vehicle energy storage system, the role of bidirectional AC-DC converter is indispensable. The system requires AC-DC converter to connect the electric vehicle energy storage system and the power grid.

[0004] At present, the topologies of bidirectional AC-DC converters based on V2G are mainly divided into two-stage, quasi-single-stage and single-stage, such as Figure 3 The structure shown is a combination of a front-stage three-phase PWM converter and a rear-stage DAB converter. It is a conventional two-stage bidirectional AC-DC converter circuit structure. It is currently widely used in the field of electric vehicle charging piles. Its topological front-stage and rear-stage structures are relatively easy to implement, and have high working reliability and complete control methods. However, the two-stage topological structure leads to a decrease in transmission efficiency, and because the intermediate DC link needs to use a large-capacity electrolytic capacitor to support the bus voltage, the starting impact current is large, and the electrolytic capacitor used is large in size and has a short service life, which in turn causes the converter volume to increase and the power density to decrease. From the perspective of the service life of the converter, it is limited. In addition, both stages of the two-stage converter require PWM chopping control, which is complex to control and has large switching losses. The topology of the quasi-single-stage converter is not much different from that of the two-stage converter, but the quasi-single-stage converter does not need to use a large-capacity electrolytic capacitor to support the bus voltage. The quasi-single-stage converter needs to be matched with a more complex control method, and the voltage range of the quasi-single-stage converter is usually subject to some restrictions. Single-stage converters can achieve higher efficiency and power density, do not require large-capacity bus capacitors, and have a relatively simple control method. However, the output voltage range of a typical single-stage converter is relatively narrow and is generally used in small and medium power applications.

[0005] It can be seen that the current AC-DC converters do not have the characteristics of low switching loss, high efficiency, high power density, simple control method, small starting impact current, wide voltage range and long service life. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a single-stage isolated AC-DC converter and system with active clamping, which has the characteristics of small switching loss, high efficiency, high power density, simple control method, small starting impact current, wide voltage range and long service life.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] In the first aspect, a single-stage isolated AC-DC converter with active clamping is proposed, comprising an AC end, an AC filter, a first rectifier / inverter circuit, an active clamping circuit, a chopper circuit unit, a DC filter and a DC end connected in sequence; the chopper circuit unit comprises an inverter / rectifier circuit, a transformer and a second rectifier / inverter circuit connected in sequence; the inverter / rectifier circuit is connected to the active clamping circuit, and the second rectifier / inverter circuit is connected to the DC filter;

[0009] The active clamping circuit is used to convert the AC signal output by the first rectifier / inverter circuit into a PWM signal; the inverter / rectifier circuit and the second rectifier / inverter circuit are used to work in a square wave inverter state with a dead zone, convert the voltage level, and realize soft switching.

[0010] Further, the AC end is an AC source or an AC load;

[0011] The DC end is a DC source or a DC load.

[0012] Furthermore, the active clamping circuit includes a switch tube S c and capacitor C1; switch tube S c The source of the active clamp circuit is used as the positive node, and the switch S c The drain is connected to the capacitor C1, and the other end of the capacitor C1 serves as the negative node of the active clamping circuit; the positive node and the negative node of the active clamping circuit are connected to the output end of the first rectifier / inverter circuit and the input end of the inverter / rectifier circuit.

[0013] Further, the AC filter adopts an L, CL or LCL structure, one end of the AC terminal is connected to the input end of the AC filter, and the output end of the AC filter is connected to the input end of the first rectifier / inverter circuit;

[0014] The DC filter adopts a C or CLC structure, the DC filter is connected to the output end of the second rectifier / inverter circuit, and the DC end is connected in parallel with the DC filter.

[0015] Furthermore, the first rectifying / inverting circuit adopts SPWM modulation or SVPWM modulation.

[0016] Furthermore, the AC end, the AC filter and the first rectifier / inverter circuit are all single-phase, three-phase or multi-phase structures.

[0017] Further, the first rectifier / inverter circuit adopts a full-bridge circuit, an interleaved full-bridge circuit or a three-level circuit;

[0018] The inverter / rectifier circuit adopts a full-bridge circuit or a half-bridge circuit;

[0019] The second rectifying / inverting circuit adopts a full-bridge circuit, a half-bridge circuit or a full-wave circuit.

[0020] Furthermore, when the converter operates in bidirectional power flow, the power devices in the first rectifier / inverter circuit, the inverter / rectifier circuit and the second rectifier / inverter circuit all use fully controlled switches; when the converter operates in AC to DC unidirectional power flow, the power devices in the second rectifier / inverter circuit use diodes; when the converter operates in DC to AC unidirectional power flow, the power devices in the inverter / rectifier circuit use diodes.

[0021] Furthermore, the chopper circuit unit includes an inverter / rectifier circuit, one or more transformers and a second rectifier / inverter circuit; multiple transformers are connected in series, and each transformer is connected to a separate second rectifier / inverter circuit; the output end of the inverter / rectifier circuit is connected to both ends of a series circuit of multiple transformers; multiple second rectifier / inverter circuits are connected in series or in parallel, and both ends of the series circuit or parallel circuit of multiple second rectifier / inverter circuits are connected to a DC filter.

[0022] In a second aspect, a single-stage isolation system with source clamping is proposed, including the single-stage isolation AC-DC converter with source clamping proposed in the first aspect.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention proposes a single-stage isolated AC-DC converter and system with active clamping. The AC-DC converter converts the AC signal output by the first rectifier / inverter circuit into a PWM signal by setting an active clamping circuit; the voltage level is converted and soft switching is realized by limiting the inverter / rectifier circuit and the second rectifier / inverter circuit to work in a square wave inversion state with a dead zone; the single-stage structure has the characteristics of high efficiency, and does not require a large-capacity bus capacitor, so that the switch loss is small, the efficiency is high, the power density is high, the control method is simple, the starting impact current is small, the service life is long, etc.; in addition, the converter can also switch the voltage range through the cooperation of a transformer and a relay to realize the characteristics of a wide voltage range, etc.

[0025] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0027] Figure 1A circuit structure and main waveform diagram of a single-stage isolated AC-DC converter with source clamping disclosed in an embodiment;

[0028] Figure 2 A circuit diagram of a single-stage isolated AC-DC converter with source clamping disclosed in an embodiment;

[0029] Figure 3 The circuit topology diagram of the conventional two-stage isolated AC-DC converter mentioned in the background technology.

[0030] Figure 4 The first example of the single-stage isolated AC-DC converter circuit topology with active clamping disclosed in the embodiment is a three-phase single-stage isolated AC-DC converter circuit topology diagram.

[0031] Figure 5 The second example of the single-stage isolated AC-DC converter circuit topology with source clamp disclosed in the embodiment is a single-phase single-stage isolated AC-DC converter circuit topology diagram.

[0032] Figure 6 The third circuit topology example of the single-stage isolated AC-DC converter with active clamp disclosed in the embodiment is a circuit topology diagram of a single-phase single-stage isolated AC-DC converter with a CL filter at the input.

[0033] Figure 7 The fourth circuit topology example of the single-stage isolated AC-DC converter circuit with active clamping disclosed in the embodiment is a circuit topology diagram of a single-phase single-stage isolated AC-DC converter input using an LCL filter.

[0034] Figure 8 This is a circuit topology example 5 of a single-stage isolated AC-DC converter circuit with source clamping disclosed in the embodiment - a circuit topology diagram of a single-phase high-power single-stage isolated AC-DC converter input using an interleaved parallel connection method.

[0035] Fig. 9 The sixth circuit topology example of the single-stage isolated AC-DC converter with source clamp disclosed in the embodiment is a circuit topology diagram of a single-phase half-bridge single-stage isolated AC-DC converter with a half-bridge structure on the primary side.

[0036] Fig.10 The seventh circuit topology example of the single-stage isolated AC-DC converter with active clamp disclosed in the embodiment is a circuit topology diagram of a single-phase half-bridge single-stage isolated AC-DC converter with a half-bridge structure on the secondary side.

[0037] Fig.11This is an example of the single-stage isolated AC-DC converter circuit topology with active clamping disclosed in the embodiment 8 - a single-phase half-bridge single-stage isolated AC-DC converter circuit topology diagram in which both the primary and secondary sides adopt a half-bridge structure.

[0038] Fig.12 The ninth circuit topology example of the single-stage isolated AC-DC converter with active clamp disclosed in the embodiment is a circuit topology diagram of a single-phase single-stage isolated AC-DC converter with a full-wave structure on the secondary side.

[0039] Fig.13 The tenth circuit topology example of a single-stage isolated AC-DC converter with active clamping disclosed in the embodiment is a T-type three-phase three-level single-winding single-stage isolated AC-DC converter circuit topology diagram.

[0040] Fig.14 The eleventh circuit topology example of the single-stage isolated AC-DC converter with active clamp disclosed in the embodiment is a circuit topology diagram of a T-type three-phase three-level three-winding single-stage isolated AC-DC converter.

[0041] Fig.15 The twelfth example of the single-stage isolated AC-DC converter circuit topology with source clamp disclosed in the embodiment is a three-phase three-level flying capacitor single-stage isolated AC-DC converter circuit topology diagram.

[0042] Fig.16 The thirteenth example of the single-stage isolated AC-DC converter circuit topology with active clamp disclosed in the embodiment is a circuit topology diagram of a type I three-phase three-level single-stage isolated AC-DC converter circuit.

[0043] Fig.17 Example 14 of the single-stage isolated AC-DC converter circuit topology with active clamping disclosed in the embodiment - a single-phase single-stage isolated AC-DC converter circuit topology diagram in which the secondary winding of the transformer has a center tap and a relay.

[0044] Fig.18 The fifteenth example of the single-stage isolated AC-DC converter circuit topology with active clamp disclosed in the embodiment is a single-phase single-stage isolated AC-DC converter circuit topology diagram in which the primary winding of the transformer has a center tap and a relay.

[0045] Fig.19 The topology diagram of the transformer primary series and output series circuit of the high-power single-stage isolated AC-DC converter with active clamping disclosed in the embodiment, in which (a) is a full-bridge structure, (b) is a transformer primary full-bridge and secondary half-bridge structure, (c) is a transformer primary half-bridge and secondary full-bridge structure, and (d) is a half-bridge structure.

[0046] Fig. 20The topology diagram of the high-power single-stage isolated AC-DC converter with active clamping disclosed in the embodiment is a primary series transformer and an output parallel circuit. In the figure, (a) is a full-bridge structure, (b) is a transformer primary full-bridge and secondary half-bridge structure, (c) is a transformer primary half-bridge and secondary full-bridge structure, and (d) is a half-bridge structure.

[0047] Fig.21 The modulation working mode topology diagram of the single-phase full-bridge single-stage isolated AC-DC converter with source clamping disclosed in the embodiment, in which (a) is the circuit state diagram of the working mode t0-t1, (b) is the circuit state diagram of the working mode t1-t2, (c) is the circuit state diagram of the working mode t2-t3, (d) is the circuit state diagram of the working mode t3-t4, (e) is the circuit state diagram of the working mode t4-t5, (f) is the circuit state diagram of the working mode t5-t6, and (g) is the circuit state diagram of the working mode t6-t7.

[0048] Fig. 22 The waveform diagram is a principle waveform diagram of the power frequency modulation of the single-phase full-bridge single-stage isolated AC-DC converter with source clamping disclosed in the embodiment.

[0049] Fig.23 This is a waveform diagram of the high-frequency modulation principle of the single-phase full-bridge single-stage isolated AC-DC converter with source clamping disclosed in the embodiment. DETAILED DESCRIPTION

[0050] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0051] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0052] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0053] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0054] Example 1

[0055] like Figure 1 , Figure 2As shown, this embodiment discloses a single-stage isolated AC-DC converter with active clamping, comprising an AC end, an AC filter, a first rectifier / inverter circuit, an active clamping circuit, a chopper circuit unit, a DC filter and a DC end connected in sequence; the chopper circuit unit comprises an inverter / rectifier circuit, a transformer and a second rectifier / inverter circuit connected in sequence; the inverter / rectifier circuit is connected to the active clamping circuit, and the second rectifier / inverter circuit is connected to the DC filter;

[0056] The active clamping circuit is used to convert the AC signal output by the first rectifier / inverter circuit into a PWM signal; the inverter / rectifier circuit and the second rectifier / inverter circuit are used to work in a square wave inverter state with a dead zone, convert the voltage level, and realize soft switching.

[0057] The AC end of this embodiment is an AC source or an AC load;

[0058] The DC end is a DC source or a DC load.

[0059] The active clamping circuit includes a switch tube S c and capacitor C1; switch tube S c The source of the active clamp circuit is used as the positive node, and the switch S c The drain of the first rectifier / inverter circuit is connected to the capacitor C1, and the other end of the capacitor C1 serves as the negative node of the active clamping circuit; the positive node and the negative node of the active clamping circuit are connected to the output end of the first rectifier / inverter circuit and the input end of the inverter / rectifier circuit; the voltage spike suppression of the first rectifier / inverter circuit and the inverter / rectifier circuit is achieved through the active clamping circuit.

[0060] The AC filter adopts an L, CL or LCL structure, one end of the AC terminal is connected to the input end of the AC filter, and the output end of the AC filter is connected to the input end of the first rectifier / inverter circuit;

[0061] The DC filter adopts a C or CLC structure, the DC filter is connected to the output end of the second rectifier / inverter circuit, and the DC end is connected in parallel with the DC filter.

[0062] Among them, the AC filter using L structure includes inductor L f , the inductor L f One end is the input end of the AC filter, and the other end is the output end of the AC filter.

[0063] The AC filter using LC structure includes inductor L f and capacitor C f , inductance L f One end and capacitor C f One end of the inductor L f The other end and capacitor C fOne end is the output end of the AC filter, and the input end of the AC filter is connected to the inductor L f and capacitor C f Lead out from the connection circuit.

[0064] The AC filter using LCL structure includes an inductor L f1 、Inductance L f2 and capacitor C f , inductance L f1 One end of the AC filter is used as the input end of the AC filter, and the inductor L f1 The other end of the inductor L f2 One end and capacitor C f One end of the inductor L is connected f2 The other end and capacitor C f The other end of each is used as the output end of the AC filter.

[0065] The DC filter adopting the C structure includes a capacitor C2.

[0066] The AC end, AC filter and first rectifier / inverter circuit of this embodiment are all single-phase, three-phase or multi-phase structures;

[0067] The first rectifier / inverter circuit adopts a full-bridge circuit, an interleaved full-bridge circuit or a three-level circuit;

[0068] The inverter / rectifier circuit adopts a full-bridge circuit or a half-bridge circuit;

[0069] The second rectifying / inverting circuit adopts a full-bridge circuit, a half-bridge circuit or a full-wave circuit.

[0070] The three-level circuit may be a T-type three-level circuit, a flying capacitor three-level circuit or an I-type three-level circuit.

[0071] The first rectifier / inverter circuit using a single-phase full-bridge circuit includes a switch tube S 1a , switch tube S 1b , switch tube S 2a And switch tube S 2b , switch tube S 1a The source and switch tube S 2a The drain connection of the switch tube S 1b The source and switch tube S 2b The input end of the first rectifier / inverter circuit is connected from the switch tube S 1a And switch tube S 2a Connection circuit and switch tube S 1b And switch tube S 2b The switch tube S 1a The drain and switch S 1b The drain connection of the switch tube S 2aThe source and switch tube S 2b The output end of the first rectifier / inverter circuit is connected from the switch tube S 1a And switch tube S 1b Connection circuit and switch tube S 2a And switch tube S 2b Lead out from the connection circuit.

[0072] The first rectifier / inverter circuit using a three-phase full-bridge circuit includes a switch tube S 1a , switch tube S 1b , switch tube S 1c , switch tube S 2a , switch tube S 2b And switch tube S 2c , switch tube S 1a The source and switch tube S 2a The drain connection of the switch tube S 1b The source and switch tube S 2b The drain connection of the switch tube S 1c The source and switch tube S 2c The input end of the first rectifier / inverter circuit is connected from the switch tube S 1a And switch tube S 2a Connection circuit, switch tube S 1b And switch tube S 2b Connection circuit and switch tube S 1c And switch tube S 2c The switch tube S 1a The drain of the switch tube S 1b The drain and switch S 1c The drain of the switch tube S 2a The source of the switch tube S 2b The source and switch tube S 2c The output end of the first rectifier / inverter circuit is connected to the source of the switch tube S 1a , switch tube S 1b And switch tube S 1c Connection circuit and switch tube S 2a , switch tube S 2b And switch tube S 2c Lead out from the connection circuit.

[0073] The first rectifier / inverter circuit using the interleaved full-bridge circuit includes a switch tube S 1a , switch tube S 1b , switch tube S 10 , switch tube S 2a , switch tube S 2b , switch tube S 20 , inductor L1 and inductor L2, switch tube S1a The source and switch tube S 2a The drain connection of the switch tube S 1b The source and switch tube S 2b The drain connection of the switch tube S 10 The source and switch tube S 20 The drain of the inductor L1 is connected to the switch tube S 1a And switch tube S 2a One end of the inductor L2 is connected to the switch tube S 1b And switch tube S 2b The other end of the inductor L1 is connected to the other end of the inductor L2; the input end of the first rectifier / inverter circuit is connected from the switch tube S 1a And switch tube S 2a The connection circuit of the inductor L1 and the inductor L2 and the switch tube S 10 And switch tube S 20 The switch tube S 1a The drain of the switch tube S 1b The drain and switch S 10 The drain of the switch tube S 2a The source of the switch tube S 2b The source and switch tube S 2c The output end of the first rectifier / inverter circuit is connected to the source of the switch tube S 1a , switch tube S 1b And switch tube S 10 Connection circuit and switch tube S 2a , switch tube S 2b And switch tube S 20 Lead out from the connection circuit. Figure 8 As shown, the input end of the first rectifier / inverter circuit drawn from the connection circuit of the inductor L1 and the inductor L2 is connected to the input end of the first rectifier / inverter circuit drawn from the switch tube S 10 And switch tube S 20 The input end of the first rectifier / inverter circuit drawn from the connection circuit is connected to the output end of the AC end, and the switch tube S 1a And switch tube S 2a The input end of the first rectifier / inverter circuit drawn out from the connecting circuit is connected to the output end of the AC filter.

[0074] The first rectifier / inverter circuit using a three-phase T-type three-level circuit includes a switch tube S 1a , switch tube S 1b , switch tube S 1c , switch tube S 2a , switch tube S 2b , switch tube S 2c , switch tube S 3a , switch tube S3b , switch tube S 3c , switch tube S 4a , switch tube S 4b And switch tube S 4c , switch tube S 1a The source and switch tube S 2a The drain connection of the switch tube S 1b The source and switch tube S 2b The drain connection of the switch tube S 1c The source and switch tube S 2c The drain connection of the switch tube S 3a The source and switch tube S 4a The source connection of the switch tube S 3b The source and switch tube S 4b The source connection of the switch tube S 3c The source and switch tube S 4c The source connection of the switch tube S 3a The drain of the switch tube S 1a And switch tube S 2a The connection circuit of the switch tube S 3b The drain of the switch tube S 1b And switch tube S 2b The connection circuit of the switch tube S 3c The drain of the switch tube S 1c And switch tube S 2c The connection circuit of the switch tube S 4a The drain of the switch tube S 4b The drain and switch S 4c The drain connection of the switch tube S 1a The drain of the switch tube S 1b The drain and switch S 1c The drain of the switch tube S 2a The source of the switch tube S 2b The source and switch tube S 2c The input end of the first rectifier / inverter circuit is connected to the source of the switch tube S 3a , switch tube S 1a And switch tube S 2a At the common connection point, the switch tube S 3b , switch tube S 1b And switch tube S 2b The common connection point and switch tube S 3c , switch tube S 1c And switch tube S 2c The output end of the first rectifier / inverter circuit is connected to the common connection point of the switch tube S 1a , switch tube S 1b And switch tube S1c The connection circuit of the switch tube S 2a , switch tube S 2b And switch tube S 2c Connection circuit and switch tube S 4a , switch tube S 4b And switch tube S 4c The common connection point is drawn out, such as Fig.14 shown.

[0075] The first rectifier / inverter circuit using a three-phase flying capacitor three-level circuit may also include a switch tube S 11a , switch tube S 11b , switch tube S 11c , switch tube S 12a , switch tube S 12b , switch tube S 12c , switch tube S 21a , switch tube S 21b , switch tube S 21c , switch tube S 22a , switch tube S 22b , switch tube S 22c , capacitor C a , capacitor C b and capacitor C c ; Switching tube S 11a The source and switch tube S 12a The drain connection of the switch tube S 21a The source and switch tube S 22a The drain connection of the switch tube S 12a The source and switch tube S 21a The drain connection, capacitor C a One end of the switch tube S 11a And switch tube S 12a The connection circuit is connected, capacitor C a The other end of the switch tube S 21a And switch tube S 22a The connection circuit is connected; the switch tube S 11b The source and switch tube S 12b The drain connection of the switch tube S 21b The source and switch tube S 22b The drain connection of the switch tube S 12b The source and switch tube S 21b The drain connection, capacitor C b One end of the switch tube S 11b And switch tube S 12b The connection circuit is connected, capacitor C b The other end of the switch tube S 21b And switch tube S 22b The connection circuit is connected; the switch tube S11c The source and switch tube S 12c The drain connection of the switch tube S 21c The source and switch tube S 22c The drain connection of the switch tube S 12c The source and switch tube S 21c The drain connection, capacitor C c One end of the switch tube S 11c And switch tube S 12c The connection circuit is connected, capacitor C c The other end of the switch tube S 21c And switch tube S 22c The input end of the first rectifier / inverter circuit is connected from the switch tube S 12a And switch tube S 21a Connection circuit, switch tube S 12b And switch tube S 21b Connection circuit and switch tube S 12c And switch tube S 21c The switch tube S 11a The drain of the switch tube S 11b The drain and switch S 11c The drain connection of the switch tube S 22a The source of the switch tube S 22b The source and switch tube S 22c The output end of the first rectifier / inverter circuit is connected from the switch tube S 11a , switch tube S 11b And switch tube S 11c Connection circuit and switch tube S 22a , switch tube S 22b And switch tube S 22c Lead out from the connection circuit, such as Fig.15 shown.

[0076] The first rectifier / inverter circuit using the three-phase I-type three-level circuit may also include a switch tube S 11a , switch tube S 11b , switch tube S 11c , switch tube S 12a , switch tube S 12b , switch tube S 12c , switch tube S 21a , switch tube S 21b , switch tube S 21c , switch tube S 22a , switch tube S 22b , switch tube S 22c , switch tube S 1a , switch tube S 1b , switch tube S 1c, switch tube S 2a , switch tube S 2b , switch tube S 2c , capacitor C c1 and capacitor C c2 ; Switching tube S 11a The source and switch tube S 12a The drain connection of the switch tube S 21a The source and switch tube S 22a The drain connection of the switch tube S 12a The source and switch tube S 21a The drain connection of the switch tube S 1a The source and switch tube S 2a The drain connection of the switch tube S 1a The drain and switch tube S 11a And switch tube S 12a The connection circuit is connected, the switch tube S 2a The source and switch tube S 21a And switch tube S 22a The connection circuit is connected; the switch tube S 11b The source and switch tube S 12b The drain connection of the switch tube S 21b The source and switch tube S 22b The drain connection of the switch tube S 12b The source and switch tube S 21b The drain connection of the switch tube S 1b The source and switch tube S 2b The drain connection of the switch tube S 1b The drain and switch tube S 11b And switch tube S 12b The connection circuit is connected, the switch tube S 2b The source and switch tube S 21b And switch tube S 22b The connection circuit is connected; the switch tube S 11c The source and switch tube S 12c The drain connection of the switch tube S 21c The source and switch tube S 22c The drain connection of the switch tube S 12c The source and switch tube S 21c The drain connection of the switch tube S 1c The source and switch tube S 2c The drain connection of the switch tube S 1c The drain and switch tube S 11c And switch tube S 12c The connection circuit is connected, the switch tube S 2c The source and switch tube S 21c And switch tube S 22cConnection circuit connection; capacitor C c1 One end and capacitor C c2 One end of the switch tube S 1a With switch tube S 2a The connection circuit is also connected to the switch tube S 1b With switch tube S 2b The connection circuit is connected; the switch tube S 1b With switch tube S 2b The connection circuit is also connected to the switch tube S 1c With switch tube S 2c The connection circuit is connected; the switch tube S 1c With switch tube S 2c The connection circuit is also connected with the capacitor C c1 and capacitor C c2 The connection circuit is connected, the switch tube S 11a The drain of the switch tube S 11b The drain of the switch tube S 11c The drain and capacitor C c1 The other end of the switch tube S 22a The source of the switch tube S 22b The source of the switch tube S 22c The source and capacitor C c2 The other end of the first rectifier / inverter circuit is connected to the input end of the switch tube S 12a And switch tube S 21a Connection circuit, switch tube S 12b And switch tube S 21b Connection circuit and switch tube S 12c And switch tube S 21c The output end of the first rectifier / inverter circuit is connected to the switch tube S 11a , switch tube S 11b , switch tube S 11c and capacitor C c1 Connection circuit and switch tube S 22a , switch tube S 22b , switch tube S 22c and capacitor C c2 Lead out from the connection circuit, such as Fig.16 shown.

[0077] The inverter / rectifier circuit using a full-bridge circuit includes a switch tube Q1, a switch tube Q2, a switch tube Q3, and a switch tube Q4. The source of the switch tube Q1 is connected to the drain of the switch tube Q3, the source of the switch tube Q2 is connected to the drain of the switch tube Q4, the drain of the switch tube Q1 is connected to the drain of the switch tube Q2, and the source of the switch tube Q3 is connected to the source of the switch tube Q4. The input end of the inverter / rectifier circuit is led out from the connection circuit between the switch tube Q1 and the switch tube Q2 and the connection circuit between the switch tube Q3 and the switch tube Q4. The output end of the inverter / rectifier circuit is led out from the connection circuit between the switch tube Q1 and the switch tube Q3 and the connection circuit between the switch tube Q2 and the switch tube Q4.

[0078] The inverter / rectifier circuit using a half-bridge circuit includes a capacitor C q1 , switch tube Q2, capacitor C q2 , switch tube Q4, capacitor C q1 One end of the capacitor C q2 The source of the switch tube Q2 is connected to the drain of the switch tube Q4; the capacitor C q2 The other end is connected to the source of the switch tube Q4, and the capacitor C q1 The other end is connected to the drain of the switch tube Q2; the input end of the inverter / rectifier circuit is connected to the capacitor C q1 The connection circuit and capacitor C of the switch tube Q2 q2 The output of the inverter / rectifier circuit is connected to the switch tube Q4. q1 and capacitor C q2 The circuit is connected to the switch tube Q2 and the switch tube Q4.

[0079] The second rectifier / inverter circuit using a full-bridge circuit includes a switch tube S1, a switch tube S2, a switch tube S3 and a switch tube S4, the source of the switch tube S1 is connected to the drain of the switch tube S3; the source of the switch tube S2 is connected to the drain of the switch tube S4; the input end of the second rectifier / inverter circuit is led out from the connection circuit between the switch tube S1 and the switch tube S3 and the connection circuit between the switch tube S2 and the switch tube S4; the drain of the switch tube S1 is connected to the drain of the switch tube S2; the source of the switch tube S3 is connected to the source of the switch tube S4; the output end of the second rectifier / inverter circuit is led out from the connection circuit between the switch tube S1 and the switch tube S2 and the connection circuit between the switch tube S3 and the switch tube S4.

[0080] The second rectifier / inverter circuit using a half-bridge circuit includes a capacitor C s1 , switch tube S1, capacitor C s2 And switch tube S2, capacitor C s1 One end of the capacitor C s2 The source of the switch tube S1 is connected to the drain of the switch tube S2; the capacitor C s2The other end is connected to the source of the switch tube S2, and the capacitor C s1 The other end of the second rectifier / inverter circuit is connected to the drain of the switch tube S1; the output end of the second rectifier / inverter circuit is connected to the drain of the switch tube S1; s1 The connection circuit of the switch tube S1 and the capacitor C s2 The input end of the inverter / rectifier circuit is connected to the capacitor C s1 With capacitor C s2 The connecting circuit of the switch tube S1 and the connecting circuit of the switch tube S2 are led out.

[0081] The second rectifier / inverter circuit using a full-wave circuit includes a switch tube S1 and a switch tube S2, and the drain of the switch tube S1 is connected to the drain of the switch tube S2; the input end of the second rectifier / inverter circuit is led out from the source of the switch tube S1 and the source of the switch tube S2; the output end of the second rectifier / inverter circuit is led out from the connection circuit of the switch tube S1 and the switch tube S2.

[0082] The first rectifier / inverter circuit of this embodiment adopts SPWM modulation or SVPWM modulation.

[0083] When the single-stage isolated AC-DC converter with active clamping disclosed in this embodiment operates in bidirectional power flow, the power devices in the first rectifier / inverter circuit, the inverter / rectifier circuit and the second rectifier / inverter circuit all use fully controlled switches; when the converter operates in AC to DC unidirectional power flow, the power devices in the second rectifier / inverter circuit use diodes; when the converter operates in DC to AC unidirectional power flow, the power devices in the inverter / rectifier circuit use diodes.

[0084] In this embodiment, the primary side of the transformer T is connected to the output end of the inverter / rectifier circuit, and the secondary side of the transformer T is connected to the input end of the second rectifier / inverter circuit. In addition, the primary side or the secondary side of the transformer adopts a tapped winding, and the primary side or the secondary side of the transformer is connected to a relay. The transformer range is switched through the relay to achieve a wide range of transformer voltage output. At the same time, the primary winding of the transformer can be connected in series or the secondary winding can be connected in series and parallel according to the circuit power level to be suitable for high-power occasions.

[0085] The present embodiment discloses a single-stage isolated AC-DC converter with active clamping, in which the effective vector / level is modulated by the first rectifier / inverter circuit, and the inverter / rectifier circuit and the second rectifier / inverter circuit work in a square wave inverter state with a dead zone, and soft switching can be realized. The single-phase first rectifier / inverter circuit adopts SPWM modulation, and the AC signal is converted into a PWM signal through the active clamping circuit; the inverter / rectifier circuit and the second rectifier / inverter circuit work in a square wave inverter state with a dead zone, and are cascaded with the transformer, which only plays the role of voltage level conversion, and soft switching can be realized. The three-phase first rectifier / inverter circuit adopts SVPWM modulation, and the AC signal is converted into a PWM signal through the active clamping circuit; the inverter / rectifier circuit and the second rectifier / inverter circuit work in a square wave inverter state with a dead zone, and are cascaded with the transformer, which only plays the role of voltage level conversion, and soft switching can be realized.

[0086] The present embodiment discloses a single-stage isolated AC-DC converter with active clamping, which retains the advantages of the single-stage AC-DC converter such as low switching loss and high efficiency, while having the characteristics of high power density, simple control method, small starting impact current, wide voltage range, long service life, etc., and is more superior than the traditional on-board bidirectional AC-DC converter applied to V2G.

[0087] like Figure 4 The figure shows a single-stage isolated AC-DC converter with a three-phase structure. In the converter, the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all three-phase structures, the first rectifier / inverter circuit adopts a full-bridge circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectifier / inverter circuit adopts a full-bridge circuit, the DC end is a DC load R, the AC end is an AC source, the output end of the AC source is connected to the three-phase filter, the output end of the three-phase filter is connected to the input end of the first rectifier / inverter circuit, the output end of the first rectifier / inverter circuit is connected to the positive node and the negative node of the active clamping circuit, the input end of the inverter / rectifier circuit is connected to the positive node and the negative node of the active clamping circuit, the output end of the inverter / rectifier circuit is connected to the primary side of the transformer T, the secondary side of the transformer T is connected to the input end of the second rectifier / inverter circuit, the input end of the second rectifier / inverter circuit is connected to the two ends of the DC filter, and the DC load R is connected in parallel with the DC filter.

[0088] like Figure 5 The figure shows a single-stage isolated AC-DC converter with a single-phase structure. In this converter, the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all single-phase structures, the first rectifier / inverter circuit adopts a full-bridge circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectifier / inverter circuit adopts a full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0089] like Figure 6 The figure shows a single-stage isolated AC-DC converter with a single-phase structure. In this converter, the AC filter adopts a CL structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all single-phase structures, the first rectifier / inverter circuit adopts a full-bridge circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectifier / inverter circuit adopts a full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0090] like Figure 7 The figure shows a single-stage isolated AC-DC converter with a single-phase structure. In this converter, the AC filter adopts an LCL structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all single-phase structures, the first rectifier / inverter circuit adopts a full-bridge circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectifier / inverter circuit adopts a full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0091] like Figure 8 The figure shows a single-stage isolated AC-DC converter using an interleaved parallel connection method. In this converter, the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end and the AC filter are both single-phase structures, the first rectifier / inverter circuit adopts an interleaved full-bridge circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectifier / inverter circuit adopts a full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0092] like Fig. 9 The figure shows a single-phase half-bridge single-stage isolated AC-DC converter, in which the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all single-phase structures, the first rectifier / inverter circuit adopts a full-bridge circuit, the inverter / rectifier circuit adopts a half-bridge circuit, the second rectifier / inverter circuit adopts a full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0093] like Fig.10 The figure shows a single-phase half-bridge single-stage isolated AC-DC converter, in which the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all single-phase structures, the first rectifier / inverter circuit adopts a full-bridge circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectifier / inverter circuit adopts a half-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0094] like Fig.11The figure shows a single-phase half-bridge single-stage isolated AC-DC converter, in which the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all single-phase structures, the first rectifier / inverter circuit adopts a full-bridge circuit, the inverter / rectifier circuit adopts a half-bridge circuit, the second rectifier / inverter circuit adopts a half-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0095] like Fig.12 The figure shows a single-phase single-stage isolated AC-DC converter, in which the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all single-phase structures, the first rectifier / inverter circuit adopts a full-bridge circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectifier / inverter circuit adopts a full-wave circuit, the DC end is a DC load R, and the AC end is an AC source.

[0096] like Fig.13 The figure shows a three-phase three-level single-stage isolated AC-DC converter, in which the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all three-phase structures, the first rectifier / inverter circuit adopts a three-phase bridge arm circuit, the inverter / rectifier circuit adopts a single-phase bridge arm circuit, the second rectifier / inverter circuit adopts a full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0097] like Fig.14 The figure shows a single-stage isolated AC-DC converter using T-type three-level for rectification / inversion. In this converter, the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectification / inversion circuit are all three-phase structures, the first rectification / inversion circuit adopts a three-phase bridge arm circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the transformer adopts a single-winding transformer, the second rectification / inversion circuit adopts a three-phase full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0098] like Fig.15 The figure shows a single-stage isolated AC-DC converter that uses a flying capacitor type three-level for rectification / inversion. In this converter, the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectification / inversion circuit are all three-phase structures, the first rectification / inversion circuit adopts a three-phase bridge arm circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectification / inversion circuit adopts a full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0099] like Fig.16The figure shows a single-stage isolated AC-DC converter which adopts I-type three-level for rectification / inversion and uses a switch tube for clamping. In this converter, the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectification / inversion circuit are all three-phase structures, the first rectification / inversion circuit adopts a three-phase bridge arm circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectification / inversion circuit adopts a full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0100] like Fig.17 The figure shows a single-stage isolated AC-DC converter with a center tap and a relay on the secondary side of the transformer. In this converter, the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all single-phase structures, the first rectifier / inverter circuit adopts a full-bridge circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectifier / inverter circuit adopts a three-phase full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0101] like Fig.18 The figure shows a single-stage isolated AC-DC converter with a center tap and a relay on the primary side of the transformer. In this converter, the AC filter adopts an L structure, the DC filter adopts a C structure, the AC end, the AC filter and the first rectifier / inverter circuit are all single-phase structures, the first rectifier / inverter circuit adopts a full-bridge circuit, the inverter / rectifier circuit adopts a full-bridge circuit, the second rectifier / inverter circuit adopts a three-phase full-bridge circuit, the DC end is a DC load R, and the AC end is an AC source.

[0102] The present embodiment discloses a single-stage isolated AC-DC converter with active clamping, wherein the chopper circuit unit includes an inverter / rectifier circuit, multiple transformers, and multiple second rectifier / inverter circuits; multiple transformers are connected in series, and each transformer is connected to a separate second rectifier / inverter circuit; the output end of the inverter / rectifier circuit is connected to the two ends of the series circuit of multiple transformers; multiple second rectifier / inverter circuits are connected in series or in parallel, and the two ends of the series circuit or parallel circuit of multiple second rectifier / inverter circuits are connected to a DC filter to achieve high power or wide voltage range applications, such as Fig.19 and Fig. 20 shown.

[0103] Fig.19 The transformer adopts the connection method of connecting the primary side in series and multiple second rectifier / inverter circuits in series. Fig.19 The first rectifier / inverter circuit, the inverter / rectifier circuit, and the second rectifier / inverter circuit in (a) are full-bridge circuits. Fig.19 In (b), the first rectifier / inverter circuit and the inverter / rectifier circuit both use full-bridge circuits, and the second rectifier / inverter circuit uses a half-bridge circuit. Fig.19In (c), the first rectifier / inverter circuit and the second rectifier / inverter circuit adopt a full-bridge circuit, and the inverter / rectifier circuit adopts a half-bridge circuit. Fig.19 In (d), the first rectifier / inverter circuit adopts a full-bridge circuit, and the second rectifier / inverter circuit and the inverter / rectifier circuit adopt a half-bridge circuit.

[0104] Fig. 20 The transformer adopts the connection method of connecting the primary side in series and multiple secondary rectifier / inverter circuits in parallel. Fig. 20 The first rectifier / inverter circuit, the inverter / rectifier circuit, and the second rectifier / inverter circuit in (a) are full-bridge circuits. Fig. 20 In (b), the first rectifier / inverter circuit and the inverter / rectifier circuit both use full-bridge circuits, and the second rectifier / inverter circuit uses a half-bridge circuit. Fig. 20 In (c), the first rectifier / inverter circuit and the second rectifier / inverter circuit adopt a full-bridge circuit, and the inverter / rectifier circuit adopts a half-bridge circuit. Fig. 20 In (d), the first rectifier / inverter circuit adopts a full-bridge circuit, and the second rectifier / inverter circuit and the inverter / rectifier circuit adopt a half-bridge circuit.

[0105] Fig.21 The diagram is a structural diagram of different operating modes of a single-phase full-bridge single-stage isolated AC-DC converter with active clamping under a high frequency cycle.

[0106] Mode 1: t0-t1, power frequency bridge switch tube S 1b It is in the on state and will remain in the on state until the modulation wave of the next half power frequency cycle comes to turn off. The high-frequency bridge switch tube S 1a The transformer primary switch tubes Q2 and Q3 are turned on, and the secondary switch tubes S2 and S3 are turned on. At this time, the power conduction state of the converter becomes Fig.21 (a) shown.

[0107] Mode 2: t1-t2, power frequency bridge switch tube S 1b Still in the on state, the high-frequency bridge switch tube S 1a Turn off, switch S 2a Conducting, active clamping circuit switch tube S c The parasitic diode is turned on and the clamp capacitor is charged to balance the input current and the transformer leakage inductance L r The current of the transformer primary switch tube Q2, Q3, and the secondary switch tube S2, S3 are in the on state, and the voltage is filtered and provided to the DC load for power supply. At this time, the power conduction state of the converter becomes Fig.21 (b) as shown.

[0108] Mode 3: t2-t3, power frequency bridge switch tube S 1b Still in the on state, the high-frequency bridge switch tube S 2aIn the on state, the active clamp circuit switch tube S c Synchronous conduction, clamping capacitor charging, to balance the input current and transformer leakage inductance L r The current of the transformer primary switch tube Q2, Q3, and the secondary switch tube S2, S3 are in the on state, and the voltage is filtered and provided to the DC load for power supply. At this time, the power conduction state of the converter becomes Fig.21 (c) as shown.

[0109] Mode 4: t3-t4, power frequency bridge switch tube S 1b Still in the on state, the high-frequency bridge switch tube S 2a In the on state, the active clamp circuit switch tube S c In the on state, the clamp capacitor balances the input current and the current of the transformer leakage inductance Lr, the transformer primary switch tubes Q2 and Q3 are turned off, the parasitic diodes of Q1 and Q4 are turned on, the secondary switch tubes S2 and S3 are turned off, and the parasitic diodes of S1 and S4 are turned on. In this process, zero voltage switching is achieved, and the voltage is filtered and provided to the DC load for power supply. At this time, the power conduction state of the converter becomes Fig.21 (d) as shown.

[0110] Mode 5: t4-t5, power frequency bridge switch tube S 1b Still in the on state, the high-frequency bridge switch tube S 2a In the on state, the active clamp circuit switch tube S c In the on state, the clamp capacitor is discharged. This process is relatively short. The primary switch tubes Q1 and Q4 of the transformer are turned on, and the secondary switch tubes S1 and S4 are turned on. In this process, zero voltage switching is achieved, and the voltage is filtered and provided to the DC load for power supply. At this time, the power conduction state of the converter becomes Fig.21 (e) as shown.

[0111] Mode 6: t5-t6, power frequency bridge switch tube S 1b Still in the on state, the high-frequency bridge switch tube S 2a In the on state, the active clamp circuit switch tube S c The transformer is turned off, the primary switch tubes Q1 and Q4, and the secondary switch tubes S1 and S4 are in the on state, and the voltage is filtered and provided to the DC load for power supply. At this time, the power conduction state of the converter becomes Fig.21 (f) as shown.

[0112] Mode 7: t6-t7, power frequency bridge switch tube S 1b Still in the on state, the high-frequency bridge switch tube S 2a Shutdown, S 1a Conducting, active clamping circuit switch tube S cIn the off state, the transformer primary switch tubes Q1 and Q4 and the secondary switch tubes S1 and S4 are in the on state. At this time, the power conduction state of the converter becomes Fig.21 (g) as shown.

[0113] Fig. 22 , Fig.23 The modulation principle waveform diagram of the proposed modulation strategy applied to a single-phase single-stage isolated AC-DC converter with source clamping, where Fig. 22 It is the principle waveform diagram of industrial frequency modulation. Fig.23 It is a high-frequency modulation principle waveform diagram of the modulation waveform.

[0114] Example 2

[0115] In this embodiment, a single-stage isolation system with source clamping is disclosed, including a single-stage isolation AC-DC converter with source clamping disclosed in Embodiment 1.

[0116] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A single-stage isolated AC-DC converter with source clamping, characterized in that: It includes an AC end, an AC filter, a first rectifier / inverter circuit, an active clamp circuit, a chopper circuit unit, a DC filter and a DC end connected in sequence; the chopper circuit unit includes an inverter / rectifier circuit, a transformer and a second rectifier / inverter circuit connected in sequence; the inverter / rectifier circuit is connected to the active clamp circuit, and the second rectifier / inverter circuit is connected to the DC filter; The active clamping circuit is used to convert the AC signal output by the first rectifier / inverter circuit into a PWM signal; the inverter / rectifier circuit and the second rectifier / inverter circuit are used to work in a square wave inverter state with a dead zone, convert the voltage level, and realize soft switching.

2. A single-stage isolated AC-DC converter with source clamping as claimed in claim 1, characterized in that: The AC end is an AC source or an AC load; The DC end is a DC source or a DC load; The AC end, the AC filter and the first rectifier / inverter circuit are all single-phase, three-phase or multi-phase structures.

3. A single-stage isolated AC-DC converter with source clamping as claimed in claim 1, characterized in that: The active clamping circuit includes a switch tube S c and capacitor C1; switch tube S c The source of the active clamp circuit is used as the positive node, and the switch S c The drain is connected to the capacitor C1, and the other end of the capacitor C1 serves as the negative node of the active clamping circuit; the positive node and the negative node of the active clamping circuit are connected to the output end of the first rectifier / inverter circuit and the input end of the inverter / rectifier circuit.

4. A single-stage isolated AC-DC converter with source clamping as claimed in claim 1, characterized in that: The AC filter adopts an L, CL or LCL structure, one end of the AC terminal is connected to the input end of the AC filter, and the output end of the AC filter is connected to the input end of the first rectifier / inverter circuit; The DC filter adopts a C or CLC structure, the DC filter is connected to the output end of the second rectifier / inverter circuit, and the DC end is connected in parallel with the DC filter.

5. A single-stage isolated AC-DC converter with source clamping as claimed in claim 1, characterized in that: The first rectifier / inverter circuit adopts SPWM modulation or SVPWM modulation.

6. A single-stage isolated AC-DC converter with source clamping as claimed in claim 1, characterized in that: The AC end, the AC filter and the first rectifier / inverter circuit are all single-phase, three-phase or multi-phase structures.

7. A single-stage isolated AC-DC converter with source clamping as claimed in claim 1, characterized in that: The first rectifier / inverter circuit adopts a full-bridge circuit, an interleaved full-bridge circuit or a three-level circuit; The inverter / rectifier circuit adopts a full-bridge circuit or a half-bridge circuit; The second rectifying / inverting circuit adopts a full-bridge circuit, a half-bridge circuit or a full-wave circuit.

8. A single-stage isolated AC-DC converter with source clamping as claimed in claim 1, characterized in that: When the converter operates in bidirectional power flow, the power devices in the first rectifier / inverter circuit, the inverter / rectifier circuit and the second rectifier / inverter circuit all use fully controlled switches; when the converter operates in AC to DC unidirectional power flow, the power devices in the second rectifier / inverter circuit use diodes; when the converter operates in DC to AC unidirectional power flow, the power devices in the inverter / rectifier circuit use diodes.

9. A single-stage isolated AC-DC converter with source clamping as claimed in claim 1, characterized in that: The chopper circuit unit includes an inverter / rectifier circuit, one or more transformers and a second rectifier / inverter circuit; multiple transformers are connected in series, and each transformer is connected to a separate second rectifier / inverter circuit; the output end of the inverter / rectifier circuit is connected to the two ends of the series circuit of multiple transformers; multiple second rectifier / inverter circuits are connected in series or in parallel, and the two ends of the series circuit or parallel circuit of multiple second rectifier / inverter circuits are connected to a DC filter.

10. A single-stage isolation system with source clamping, characterized in that: A single-stage isolated AC-DC converter with source clamping comprising the one described in any one of claims 1-9.

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