Single-stage AC-DC converter for high-frequency isolated power factor correction

Abstract

The present invention provides a single-stage AC / DC converter for realizing high-frequency isolated power factor correction, and relates to the technical field of converters. The AC / DC converter of the present invention includes an AC module with a transformer, an H4 full-bridge module, a third switch, and a switch group that satisfies a bidirectional current path; the AC module with a transformer includes a first inductor, an intermediate capacitor, a second inductor, and a transformer. The first end of the switch group that satisfies the bidirectional current path is connected to the common end of the first inductor and the intermediate capacitor, and the second end is connected to the common end of the external AC power supply and the transformer; when the single-stage AC / DC converter is working, the switch group that satisfies the bidirectional current path is complementary to the third switch. Compared with equipment such as a two-stage energy conversion configuration, the AC / DC converter of an embodiment of the present invention is equivalent to an isolated single-stage SEPIC‑PFC converter of a one-stage energy conversion, which has a simple circuit structure, is easy to control, and adopts a one-stage architecture to improve efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of converters, and in particular to a single-stage AC / DC converter for realizing high-frequency isolation power factor correction. Background Art

[0002] As a clean secondary energy source, electric energy is widely used in a variety of application scenarios. In special situations such as deep sea wells, space, biomedicine, and mines, higher requirements are placed on the safety and reliability of electric energy use. In the actual application of active three-phase rectifiers, two-stage power converters are usually required. The front stage realizes the power factor correction function, and the rear stage realizes the isolation of the output end and the power supply while adjusting the output voltage. However, the two-stage circuit increases the use of components, thereby increasing the manufacturing cost of the whole machine. In addition, the front and rear stage circuits require more voltage and current sensors, and the control circuit is complex, which reduces the reliability of the system.

[0003] By using a converter based on primary energy conversion, power factor correction and output voltage regulation can be achieved, and the converter itself can be isolated, which is conducive to reducing the cost and control difficulty of the three-phase rectifier and improving the power density. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies of the prior art, the present invention provides a single-stage AC-DC converter for realizing high-frequency isolated power factor correction, thereby solving the technical problem of low efficiency of the prior AC-DC converter.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a single-stage AC-DC converter for realizing high-frequency isolated power factor correction, comprising an AC module with a transformer, an H4 full-bridge module, a third switch, and a switch group satisfying a bidirectional current path;

[0009] Wherein, the AC modules with transformers each include four ports; the H4 full-bridge module includes four bridge arms, the common end of the first bridge arm and the second bridge arm is the first end of the H4 full-bridge module, the common end of the third bridge arm and the fourth bridge arm is the second end of the H4 full-bridge module, the common end of the first bridge arm and the third bridge arm is the third end of the H4 full-bridge module, and the common end of the second bridge arm and the fourth bridge arm is the fourth end of the H4 full-bridge module;

[0010] The AC module with transformer includes a first inductor, an intermediate capacitor, a second inductor and a transformer; wherein the first end of the first inductor is the first port of the AC module, the second end of the first inductor is connected to the first end of the first coil of the transformer via the intermediate capacitor, the second end of the first coil is the second port of the AC module, and the second inductor is connected in parallel with the first coil; the first end of the second coil of the transformer is the third port of the AC module, and the second end of the second coil is the fourth port of the AC module;

[0011] The first port and the second port of the AC module with a transformer are connected to an external AC power source;

[0012] The third port and the third port of the AC module are connected to the third end and the fourth end of the H4 full-bridge module respectively;

[0013] The first end of the H4 full-bridge module is connected to the first end of the load, and the second end is connected to the second end of the load via the third switch;

[0014] A first end of the switch group satisfying a bidirectional current path is connected to a common end of the first inductor and the intermediate capacitor, and a second end is connected to a common end of the external AC power supply and the transformer;

[0015] When the single-stage AC / DC converter is working, the switch group satisfying the bidirectional current path is complementarily turned on with the third switch.

[0016] Preferably, the H4 full-bridge module includes 4 diodes, or 4 switches, or 4 switching tubes.

[0017] Preferably, the switch group satisfying the bidirectional current path includes two switch tubes with freewheeling diodes, and the two switch tubes are top-to-top switch tubes.

[0018] Preferably, the third switch is a switch tube or a single-pole switch.

[0019] In a second aspect, the present invention provides a single-stage AC-DC converter for realizing high-frequency isolated power factor correction, comprising three AC modules with transformers, three DC modules, a seventh switch, and three switch groups satisfying a bidirectional current path;

[0020] Each AC module with a transformer includes four ports; each DC module includes three ports, wherein the first ports of the three DC modules are connected together, the third ports of the three DC modules are connected together, and the second port is located between the first port and the third port and is an external connection port;

[0021] The three AC modules with transformers all include a first inductor, an intermediate capacitor, a second inductor and a transformer; wherein the first end of the first inductor is the first port of the AC module, the second end of the first inductor is connected to the first end of the first coil of the transformer via the intermediate capacitor, the second end of the first coil is the second port of the AC module, and the second inductor is connected in parallel with the second coil; the first end of the second coil of the transformer is the third port of the AC module, and the second end of the second coil is the fourth port of the AC module;

[0022] The first port of each AC module with a transformer is respectively connected to the A, B, and C phases of the three-phase power grid, and the second ports of the three AC modules with transformers are connected together;

[0023] The third ports of the three AC modules with transformers are respectively connected to the second ports of the three DC modules, and the fourth ports of the three AC modules with transformers are connected together;

[0024] The common end of the first inductor and the intermediate capacitor of each AC module with a transformer is connected to the second port of the AC module via a switch tube group that satisfies a bidirectional current path;

[0025] When the single-stage AC / DC converter is working, the current direction in the three DC modules is that the third port flows to the second end, and the second end flows to the first port; the three switch groups satisfying the bidirectional current path are complementarily turned on with the seventh switch;

[0026] The single-stage AC / DC converter can realize bidirectional current flow. When the current flows from the AC module to the DC module, the common end of the first ports of the three DC modules is connected to the first end of the load, and the common end of the third ports of the three DC modules is connected to the second end of the load via the seventh switch; when the current flows from the DC module to the AC module, the common end of the first ends of the three DC modules is connected to the positive pole of the DC power supply, and the common end of the third ends of the three DC modules is connected to the negative pole of the DC power supply via the seventh switch.

[0027] Preferably, in the DC module, a switch tube or a single-pole switch is connected between the first port and the second port, and between the second port and the third port.

[0028] Preferably, in the DC module, diodes are connected between the first port and the second port and between the second port and the third port; wherein the cathode of the first diode is connected to the first port, and the anode is connected to the second port; wherein the cathode of the second diode is connected to the second port, and the anode is connected to the third port.

[0029] Preferably, the seventh switch is a switch tube or a single-pole switch.

[0030] Preferably, the output voltage step-up and step-down control is achieved by changing the duty ratio of three switch groups satisfying the bidirectional current path.

[0031] Preferably, the switch group satisfying the bidirectional current path includes two switch tubes with freewheeling diodes.

[0032] (III) Beneficial effects

[0033] The present invention provides a three-phase single-stage AC / DC converter for realizing high-frequency isolated power factor correction. Compared with the prior art, it has the following beneficial effects:

[0034] Compared with equipment such as a two-stage energy conversion configuration, the AC-DC converter of the embodiment of the present invention is equivalent to an isolated single-stage SEPIC-PFC converter with a one-stage energy conversion. It has a simple circuit structure, does not require a bus capacitor, reduces costs, adopts a one-stage architecture, and improves efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is a circuit structure diagram of an existing three-phase two-stage PFC rectifier;

[0037] Figure 2 A circuit diagram of an existing three-phase two-stage PFC rectifier;

[0038] Figure 3 A circuit diagram of an existing three-phase two-stage PFC rectifier in which a three-phase six-switch PFC is used in the front stage and an isolated DC / DC converter is used in the rear stage;

[0039] Figure 4 is a circuit structure diagram of a single-stage AC / DC converter in Example 1;

[0040] Figure 5 for Figure 4 The specific circuit diagram of the circuit structure diagram shown;

[0041] Figure 6 for Figure 5 The circuit diagram of the single-stage AC / DC converter in off-grid mode when realizing bidirectional current flow;

[0042] Figure 7 is a circuit structure diagram of a single-stage AC / DC converter in Example 2;

[0043] Figure 8 for Figure 7 Detailed circuit diagram of the circuit structure diagram;

[0044] Fig. 9 for Figure 8 The circuit diagram of the single-stage AC / DC converter in grid-connected mode when realizing bidirectional current flow;

[0045] Fig.10 for Figure 8 The operating mode 1 of the single-stage AC-DC converter shown;

[0046] Fig.11 for Figure 8 The operating mode 2 of the single-stage AC-DC converter shown;

[0047] Fig.12 for Figure 8 The operating mode 3 of the single-stage AC-DC converter shown;

[0048] Fig.13 for Figure 8 The operating mode 4 of the single-stage AC-DC converter shown;

[0049] Fig.14 for Figure 8 The operating mode 5 of the single-stage AC-DC converter shown;

[0050] Fig.15 for Figure 8 The operating mode 6 of the single-stage AC-DC converter shown;

[0051] Fig.16 for Figure 8 The operating mode 7 of the single-stage AC-DC converter shown;

[0052] Fig.17 for Figure 8 The operating mode 8 of the single-stage AC-DC converter shown;

[0053] Fig.18 for Figure 8 The circuit diagram shown achieves the output voltage and input current tracking the input voltage phase waveform during boosting;

[0054] Fig.19 for Fig.18 The A phase in the middle outputs a local amplified waveform;

[0055] Fig. 20 for Figure 8 The circuit diagram shown realizes the output voltage and input current tracking the input voltage phase waveform during voltage reduction;

[0056] Fig.21 for Fig. 20 The A phase in the middle outputs a local amplified waveform. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are 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 are within the scope of protection of the present invention.

[0058] It should be noted that, for the convenience of description, the switch IGBT is used to represent the controllable (on and off) switch tube in the embodiment of the present invention, but the switch tube in the present invention is not limited to IGBT. Take IGBT as an example for explanation. The first end of the IGBT refers to the collector, the second end refers to the emitter, and the control end refers to the gate. A driving control signal is applied to the control end of each switch tube in the embodiment of the present invention. For the sake of brevity, it will not be repeated later. The power switch tube in the embodiment of the present invention can also be implemented by other controllable switch tube devices other than IGBT, such as MOSFET. At the same time, in order to ensure the normal operation of each switch device in the embodiment of the present invention, a freewheeling diode needs to be connected in parallel to each switch device. The parallel connection direction of the freewheeling diode is related to the type of the switch device. The technician can set it according to the type of the switch device, which is not limited here. If not specified, the switch device defaults to including a freewheeling diode, which will be pointed out in this embodiment in special cases.

[0059] The embodiment of the present application solves the technical problem of low efficiency of existing AC / DC converters by providing a single-stage AC / DC converter that realizes high-frequency isolated power factor correction. The one-stage energy conversion architecture is used to directly convert AC input into DC output, and no electrolytic capacitor is required to increase the life of the converter, thereby achieving high efficiency and long service life.

[0060] The technical solution in the embodiment of the present application is to solve the above technical problems, and the overall idea is as follows:

[0061] There is an active harmonic suppression scheme for suppressing the high-order harmonics caused by nonlinear power electronic equipment, namely power factor correction technology. The existing AC / DC converter generally converts the AC voltage of the power grid into DC voltage through the front-stage AC / DC converter, and then converts it into the required DC voltage through the DC / DC converter. Its structure is as follows Figure 1 As shown, its advantage is that the two-stage type is conducive to independent control of the front and rear stages, and the input and output waveforms have good quality; but its disadvantage is that since the electric energy is converted twice, the efficiency and power density are further optimized.

[0062] Figure 2 , Figure 3 Both are existing two-stage energy conversions. Figure 2It first passes through uncontrolled rectification of AC / DC, and then outputs DC voltage through Boost. It is the simplest topology in the three-phase active power factor correction circuit. Figure 3 The front stage uses a three-phase six-switch PFC, and the back stage uses an isolated DC / DC converter. Figure 2 still Figure 3 , its energy undergoes two-stage conversion, and the efficiency is low.

[0063] In order to solve the problems of the prior art, the embodiment of the present invention proposes a single-stage AC / DC converter that realizes high-frequency isolated power factor correction. The single-stage AC / DC converter uses a one-stage energy conversion to realize AC / DC conversion, replacing the mainstream AC / DC+DC / DC two-stage architecture, achieving high efficiency, and at the same time, ensuring the smoothness of the DC output. By adopting open-loop control, a standard DC voltage output with good waveform quality can be achieved. In short, the structure and control are simple, the intermediate electrolytic capacitor is omitted, the durability of the converter is improved, the number of system flagships is saved, the operating efficiency of the system is improved, the system cost is greatly reduced, the system volume is effectively reduced, and the power density is improved.

[0064] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0065] Embodiment 1:

[0066] The embodiment of the present invention provides a single-stage AC-DC converter for realizing high-frequency isolated power factor correction, such as Figure 4 As shown, it includes an AC module with a transformer, an H4 full-bridge module, a third switch, and a switch group that satisfies a bidirectional current path;

[0067] Wherein, the AC modules with transformers each include four ports; the H4 full-bridge module includes four bridge arms, the common end of the first bridge arm and the second bridge arm is the first end of the H4 full-bridge module, the common end of the third bridge arm and the fourth bridge arm is the second end of the H4 full-bridge module, the common end of the first bridge arm and the third bridge arm is the third end of the H4 full-bridge module, and the common end of the second bridge arm and the fourth bridge arm is the fourth end of the H4 full-bridge module;

[0068] The AC module with transformer includes a first inductor, an intermediate capacitor, a second inductor and a transformer; wherein the first end of the first inductor is the first port of the AC module, the second end of the first inductor is connected to the first end of the first coil of the transformer via the intermediate capacitor, the second end of the first coil is the second port of the AC module, and the second inductor is connected in parallel with the first coil; the first end of the second coil of the transformer is the third port of the AC module, and the second end of the second coil is the fourth port of the AC module;

[0069] The first port and the second port of the AC module with a transformer are connected to an external AC power source;

[0070] The third port and the third port of the AC module are connected to the third end and the fourth end of the H4 full-bridge module respectively;

[0071] The first end of the H4 full-bridge module is connected to the first end of the load, and the second end is connected to the second end of the load via the third switch;

[0072] A first end of the switch group satisfying a bidirectional current path is connected to a common end of the first inductor and the intermediate capacitor, and a second end is connected to a common end of the external AC power supply and the transformer;

[0073] When the single-stage AC / DC converter is working, the switch group satisfying the bidirectional current path is complementarily turned on with the third switch.

[0074] It should be noted that, in the specific implementation process, the switch group satisfying the bidirectional current path in this embodiment includes a single-pole switch, and may also include a switch tube combination satisfying the bidirectional current path consisting of two switch tubes with freewheeling diodes. The four bridge arms of the H4 full-bridge module may be switch tubes or diodes. Figure 5 As shown, the switch group that satisfies the bidirectional current path here is a switch tube group that satisfies the bidirectional current path composed of two switch tubes with freewheeling diodes, and the H4 full-bridge module is four diodes.

[0075] It should be noted that the single-stage AC-DC converter of the embodiment of the present invention can also realize bidirectional current flow, that is, the first end of the H4 full-bridge module is connected to the positive electrode of the DC power supply, and the second end is connected to the negative electrode of the DC power supply via the third switch. In the grid-connected mode, the first port and the second port of the AC module are connected to the external AC power supply. In the off-grid mode, Figure 6 , the first port and the second port of the AC module are connected to the load.

[0076] Example 2

[0077] The embodiment of the present invention provides a single-stage AC-DC converter for realizing high-frequency isolated power factor correction. The single-stage AC-DC converter is a single-stage three-phase AC-DC converter. Figure 7 As shown, it includes three AC modules with transformers, three DC modules, a seventh switch and three switch groups that meet bidirectional current paths;

[0078] Each AC module with a transformer includes four ports; each DC module includes three ports, wherein the first ports of the three DC modules are connected together, the third ports of the three DC modules are connected together, and the second port is located between the first port and the third port and is an external connection port;

[0079] The three AC modules with transformers all include a first inductor, an intermediate capacitor, a second inductor and a transformer; wherein the first end of the first inductor is the first port of the AC module, the second end of the first inductor is connected to the first end of the first coil of the transformer via the intermediate capacitor, the second end of the first coil is the second port of the AC module, and the second inductor is connected in parallel with the second coil; the first end of the second coil of the transformer is the third port of the AC module, and the second end of the second coil is the fourth port of the AC module;

[0080] The first port of each AC module with a transformer is respectively connected to the A, B, and C phases of the three-phase power grid, and the second ports of the three AC modules with transformers are connected together;

[0081] The third ports of the three AC modules with transformers are respectively connected to the second ports of the three DC modules, and the fourth ports of the three AC modules with transformers are connected together;

[0082] The common end of the first ports of the three DC modules is connected to the first end of the load, and the common end of the third ports of the three DC modules is connected to the second end of the load via the seventh switch;

[0083] The common end of the first inductor and the intermediate capacitor of each AC module with a transformer is connected to the second port of the AC module via a switch tube group that satisfies a bidirectional current path;

[0084] When the single-stage AC / DC converter is working, the current direction in the three DC modules is that the third port flows to the second end, and the second end flows to the first port; the three switch groups satisfying the bidirectional current path are complementarily turned on with the seventh switch.

[0085] It should be noted that, in the specific implementation process, the three switch groups satisfying the bidirectional current path in this embodiment include single-pole switches, and may also include a switch tube combination satisfying the bidirectional current path consisting of two switch tubes with freewheeling diodes. Switches or diodes may be connected between the first port and the second port, and between the second port and the third port in the DC module to realize the current direction of the third port flowing to the second port, and the second port flowing to the first port. Figure 8 As shown, the switch group satisfying the bidirectional current path here is a switch tube group satisfying the bidirectional current path composed of two switch tubes with freewheeling diodes, and the DC module includes two diodes.

[0086] It should be noted that the single-stage AC-DC converter of the embodiment of the present invention can also realize bidirectional current flow, that is, the common end of the first ends of the three DC modules is connected to the positive electrode of the DC power supply, and the common end of the third ends of the three DC modules is connected to the negative electrode of the DC power supply via the seventh switch. In the grid-connected mode, Fig. 9As shown, the first port and the second port of the AC module are connected to an external AC power source, and in the off-grid mode, the first port and the second port of the AC module are connected to a load.

[0087] Below Figure 8 Taking the circuit diagram shown in FIG. 1 as an example, a modal analysis is performed on a single-stage AC-DC converter for realizing high-frequency isolated power factor correction according to an embodiment of the present invention.

[0088] The single-stage AC-DC converter for realizing high-frequency isolated power factor correction can operate in CCM mode (continuous current mode) and DCM mode (discontinuous current mode).

[0089] Taking the DCM mode as an example, the switch devices S1, S2, S3, S4, S5, and S6 are mutually opposite switches. The three-phase single-stage AC-DC converter has a total of 8 operating modes. The states of the switch devices and the current flow in each mode are described as follows.

[0090] Since each switch tube is connected in parallel with a diode, for convenience, the signals of the switch tubes S1-S6 are the same, and the signal of the switch tube S7 is opposite to the signal of the switch tube S1-S6. And divide one power frequency cycle of the input sinusoidal AC voltage into 12 parts, and select one of them 30°: |V c |>|V a |>|V b |, and V c <0,V a >V b >0. Among them, V a 、V b 、V c It is the voltage of three-phase output of A, B and C.

[0091] Working mode 1: Fig.10 As shown, the switch tubes S1-S6 are turned on, and the switch tube S7 is turned off. The current flow path of phase A is V a →L 11 →S1→S2, V a →L 11 →C1→L 12 , C0→load, at this time the grid supplies the inductor L 11 Charging and energy storage, the voltage on C1 is positive on the left and negative on the right for inductor L 12 Discharge, , , Under the action of reverse voltage, it gradually decreases (the voltage on C1 and C2 is positive on the left and negative on the right, and the voltage on C3 is negative on the left and positive on the right). At this time, capacitor C0 supplies power to the load. Similarly, the analysis of the current flow path of phases B and C is the same as that of phase A.

[0092] Working mode 2: Fig.11As shown, the switches S1-S6 are still on, and S7 is still off. The difference from mode 1 is , , 在 The previous mode decreases to zero, and then flows in the reverse direction, and the current begins to increase. At this time, the S1-S6 conduction stage ends.

[0093] Working mode 3: Fig.12 As shown, the switch tubes S1-S6 are turned off, and the switch tube S7 is turned on. The current flow path of phase A is V a →L 11 →C1 and transformer primary (first coil), transformer secondary (second coil) →D1 →C0 and load →S7, inductor L 12 Also continue to flow to the load, at this time the grid and inductor L 11 For C1 and L 12 And transfer energy to the secondary side of the transformer. , , Gradually decreases, and at this time L 12 , L 22 , L 32 They bear (1 / 3)nVo, (1 / 3)nVo, and (2 / 3)nVo respectively. Similarly, the current flow path analysis of phases B and C is the same as that of phase A.

[0094] Working mode 4: Fig.13 As shown, the switch tubes S1-S6 are turned off, and the switch tube S7 is turned on. The difference between the current flow path of phase A and mode 3 is that due to V b The absolute value is the smallest, then L 22 Current on First it decreases to zero and then reverses.

[0095] Working mode 5: Fig.14 As shown, the switch tubes S1-S6 are turned off and the switch tube S7 is turned on. The difference between the current flow path of phase A and mode 4 is that when the inductor L 22 Current on Increase in the opposite direction to L 21 When the currents on the A and C phases are the same and in the same direction, the primary current of the transformer is zero. At this time, the current on the diode D3 is zero, and D3 is forced to turn off. The energy is then transmitted to the load through the A and C phases.

[0096] Working mode 6: Fig.15 As shown, the switch tubes S1-S6 are turned off, and the switch tube S7 is turned on. c |>|V a |, then the inductance L 32 Current on Reverse direction first, energy transmission is still from A and C to the load.

[0097] Working mode 7: Fig.16 As shown, the switch tubes S1-S6 are turned off, and the switch tube S7 is turned on. 12 Current on In the reverse direction, the energy transmission is still from phases A and C to the load.

[0098] Working mode 8: Fig.17 As shown, the switches S1-S6 are turned off and the switch S7 is turned on. 12 The current on the inductor increases in the reverse direction to the inductor L 11 The current on the inductor L 32 The current on the inductor increases in the reverse direction to the inductor L 31 When the current on, there is no current on the primary side of the A and C phase transformers, all the diodes in the subsequent stage are turned off, and energy is provided to the load through capacitor C0.

[0099] When the output current is continuous (CCM), taking phase A as an example, the voltage gain corresponding to each switching cycle in the circuit is M The calculation formula is as follows:

[0100] =

[0101] The ratio of the primary side to the secondary side of the transformer is n, D is the duty cycle of the switch group, and 1-D is the duty cycle of the seventh switch. Compared with previous solutions, this single-stage AC-DC converter can achieve boost and buck rectification modes in one stage by changing the transformer ratio and duty cycle. With appropriate control, it also has a power factor correction function.

[0102] When the output current is discontinuous (DCM): Taking phase A as an example, the calculation formula of the voltage gain M corresponding to each switching cycle in the circuit is as follows:

[0103]

[0104] in, , x=1,2,3, in phase A, For L 11 and L 12 The equivalent inductance is fs; the switching frequency is fs; the load is represented by R0; D is the duty cycle of the front switch group; 1-D is the duty cycle of the seventh switch.

[0105] Compared with previous solutions, this topology can achieve boost and buck rectification modes in one stage by changing the duty cycle and switching frequency when the current is intermittent. With appropriate control, it also has a power factor correction function.

[0106] It should be noted that when designing the AC-DC converter, the voltage can be increased or decreased by the turns ratio of the transformer. In general, the voltage can be increased or decreased by changing the duty cycle and the turns ratio of the transformer.

[0107] Compared with the general one-stage energy conversion equipment, when the AC-DC converter of the embodiment of the present invention is in the step-up and step-down state, the subsequent diode will not have a surge current. The simulation waveform of the AC-DC converter of the embodiment of the present invention to achieve the step-up process is as follows: Fig.18 and Fig.19 As shown, the input voltage is 155V and the output voltage is 280V.

[0108] The simulation waveform of the voltage reduction process of the AC / DC converter according to the embodiment of the present invention is as follows: Fig. 20 and Fig.21 Its input voltage is 155V and its output voltage is 110V.

[0109] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0110] 1. Compared with equipment such as a two-stage energy conversion configuration, the single-stage AC-DC converter for realizing high-frequency isolated power factor correction in the embodiment of the present invention has a simple circuit structure, is easy to control, adopts a one-stage architecture, and improves efficiency.

[0111] 2. The embodiment of the present invention saves the number of system components while achieving power factor correction and AC / DC stable output voltage (especially to avoid impact current in the output diode, the topology only needs to connect a switch tube at the output stage), thereby greatly reducing costs while improving system efficiency and reducing system size.

[0112] 3. The embodiment of the present invention adopts open-loop control to achieve standard DC voltage output with good waveform quality, ensuring the smoothness of DC output.

[0113] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0114] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single-stage AC-DC converter for high-frequency isolated power factor correction, characterized in that: It includes an AC module with a transformer, an H4 full-bridge module, a third switch, and a switch group that satisfies a bidirectional current path; Wherein, the AC modules with transformers each include four ports; the H4 full-bridge module includes four bridge arms, the common end of the first bridge arm and the second bridge arm is the first end of the H4 full-bridge module, the common end of the third bridge arm and the fourth bridge arm is the second end of the H4 full-bridge module, the common end of the first bridge arm and the third bridge arm is the third end of the H4 full-bridge module, and the common end of the second bridge arm and the fourth bridge arm is the fourth end of the H4 full-bridge module; The AC module with transformer includes a first inductor, an intermediate capacitor, a second inductor and a transformer; wherein the first end of the first inductor is the first port of the AC module, the second end of the first inductor is connected to the first end of the first coil of the transformer via the intermediate capacitor, the second end of the first coil is the second port of the AC module, and the second inductor is connected in parallel with the first coil; the first end of the second coil of the transformer is the third port of the AC module, and the second end of the second coil is the fourth port of the AC module; The first port and the second port of the AC module with a transformer are connected to an external AC power source; The third port and the third port of the AC module are connected to the third end and the fourth end of the H4 full-bridge module respectively; The first end of the H4 full-bridge module is connected to the first end of the load, and the second end is connected to the second end of the load via the third switch; A first end of the switch group satisfying a bidirectional current path is connected to a common end of the first inductor and the intermediate capacitor, and a second end is connected to a common end of the external AC power supply and the transformer; When the single-stage AC / DC converter is working, the switch group satisfying the bidirectional current path is complementarily turned on with the third switch.

2. The single-stage AC-DC converter for realizing high-frequency isolated power factor correction according to claim 1, characterized in that: The H4 full-bridge module includes 4 diodes, or 4 switches, or 4 switching tubes.

3. The single-stage AC-DC converter for realizing high-frequency isolated power factor correction according to claim 1, characterized in that: The switch group satisfying the bidirectional current path includes two switch tubes with freewheeling diodes, and the two switch tubes are top-to-top switch tubes.

4. The single-stage AC-DC converter for realizing high-frequency isolated power factor correction according to claim 1, characterized in that: The third switch is a switch tube or a single-pole switch.

5. A single-stage AC-DC converter for high-frequency isolated power factor correction, characterized in that: It includes three AC modules with transformers, three DC modules, a seventh switch and three switch groups satisfying a bidirectional current path; Each AC module with a transformer includes four ports; each DC module includes three ports, wherein the first ports of the three DC modules are connected together, the third ports of the three DC modules are connected together, and the second port is located between the first port and the third port and is an external connection port; The three AC modules with transformers all include a first inductor, an intermediate capacitor, a second inductor and a transformer; wherein the first end of the first inductor is the first port of the AC module, the second end of the first inductor is connected to the first end of the first coil of the transformer via the intermediate capacitor, the second end of the first coil is the second port of the AC module, and the second inductor is connected in parallel with the second coil; the first end of the second coil of the transformer is the third port of the AC module, and the second end of the second coil is the fourth port of the AC module; The first port of each AC module with a transformer is respectively connected to the A, B, and C phases of the three-phase power grid, and the second ports of the three AC modules with transformers are connected together; The third ports of the three AC modules with transformers are respectively connected to the second ports of the three DC modules, and the fourth ports of the three AC modules with transformers are connected together; The common end of the first inductor and the intermediate capacitor of each AC module with a transformer is connected to the second port of the AC module via a switch tube group that satisfies a bidirectional current path; When the single-stage AC / DC converter is working, the current direction in the three DC modules is that the third port flows to the second end, and the second end flows to the first port; the three switch groups satisfying the bidirectional current path are complementarily turned on with the seventh switch; The single-stage AC / DC converter can realize bidirectional current flow. When the current flows from the AC module to the DC module, the common end of the first ports of the three DC modules is connected to the first end of the load, and the common end of the third ports of the three DC modules is connected to the second end of the load via the seventh switch; when the current flows from the DC module to the AC module, the common end of the first ends of the three DC modules is connected to the positive pole of the DC power supply, and the common end of the third ends of the three DC modules is connected to the negative pole of the DC power supply via the seventh switch.

6. A single-stage AC-DC converter for realizing high-frequency isolated power factor correction as claimed in claim 5, characterized in that: In the DC module, a switch tube or a single-pole switch is connected between the first port and the second port, and between the second port and the third port.

7. The single-stage AC-DC converter for realizing high-frequency isolated power factor correction as claimed in claim 5, characterized in that: In the DC module, diodes are connected between the first port and the second port, and between the second port and the third port; wherein the cathode of the first diode is connected to the first port, and the anode is connected to the second port; and the cathode of the second diode is connected to the second port, and the anode is connected to the third port.

8. The single-stage AC-DC converter for realizing high-frequency isolated power factor correction as claimed in claim 5, characterized in that: The seventh switch is a switch tube or a single-pole switch.

9. The single-stage AC-DC converter for realizing high-frequency isolated power factor correction according to any one of claims 5 to 8, characterized in that: The output voltage step-up and step-down control is achieved by changing the duty ratio of three switch groups that satisfy the bidirectional current path.

10. The single-stage AC-DC converter for realizing high-frequency isolated power factor correction according to any one of claims 5 to 8, characterized in that: The switch group satisfying the bidirectional current path includes two switch tubes with freewheeling diodes.

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