Single-stage bridgeless AC-AC converter and control method and application thereof

Abstract

The invention relates to the technical field of switching power supplies, and provides a single-stage bridgeless alternating current-alternating current converter device, a control method and application of the single-stage bridgeless alternating current-alternating current converter device. The single-stage bridgeless AC-AC converter comprises an input inductor Lg, a low-frequency bridge arm, a high-frequency bridge arm, a bus capacitor Cc, a resonant capacitor Cr, a resonant inductor Lr, a transformer T, a secondary bidirectional switch network, an output filter capacitor Co and a load Ro. The complex circuit structure of a traditional alternating current-alternating current converter device is simplified, the device has the advantages of being few in magnetic element, low in circuit cost, easy to control and the like, meanwhile, the soft switching performance of a resonant converter is achieved so as to achieve high efficiency and high power density, and the device is suitable for application occasions such as power electronic transformers.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to a single-stage bridgeless AC-AC converter device, a control method and applications thereof. Background Art

[0002] Power electronic transformer is a power electronic conversion structure that integrates power electronic switching devices with high-frequency transformers to realize the conversion of electric energy with one power characteristic into electric energy with another power characteristic. The traditional transformer process is simple and the technology is mature, but its disadvantages are also obvious. The main problems are large size, heavy weight, and poor power quality. In addition, when a load current fault occurs, it cannot play a protective role, and it is easy to cause a sharp increase in primary current, resulting in a short circuit, or even damage the transformer.

[0003] Compared with traditional transformers, power electronic transformers are not only small in size and light in weight, but also can improve the quality of electric energy. They have good input and output characteristics under full load rated operation and harmonic pollution conditions. Therefore, they are receiving more and more attention in the power electronics industry, energy Internet, civil use and other fields that require safe electricity use.

[0004] like Figure 1 As shown in the figure, the common power electronic transformer at present first converts the alternating voltage of the mains into direct current, and then forms an inverter through power switching devices and electronic components to convert the direct current into high-frequency alternating current, and outputs another form of alternating voltage through the action of the high-frequency transformer, and then performs level flipping after secondary rectification before supplying it to the electrical appliances. In this power electronic transformer with a DC link, since additional hardware components such as rectifier bridges and inverters are required, energy transmission involves multiple conversion stages and paths, and each conversion will consume a certain amount of energy, which restricts the conversion efficiency of the whole machine, and the overall complexity and cost of the system are relatively high. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the existing technology, the present invention proposes a single-stage bridgeless AC-AC converter circuit structure, which reduces hardware components and complexity and forms a new circuit topology. Compared with the existing technology, the proposed single-stage AC-AC converter can greatly simplify the circuit structure and control complexity, reduce circuit costs, and is suitable for various forms of input and output voltage requirements. At the same time, the structure can utilize the design of LLC resonant converter, which is convenient for magnetic integration, and can further reduce the volume and weight of the converter and improve power density.

[0006] The technical solution of the present invention is:

[0007] A single-stage bridgeless AC-AC converter, comprising: an input inductor L g , low frequency bridge arm, high frequency bridge arm, bus capacitor Cc , resonant capacitor C r , resonant inductor L r , transformer T, secondary bidirectional switch network, output filter capacitor C o and load R o ;

[0008] The low-frequency bridge arm includes a switch tube Q 1 And the switch tube Q 2 The high frequency bridge arm includes a switch tube Q 3 And the switch tube Q 4 ;

[0009] The AC input voltage source includes a first and a second output terminal, the input inductor L g The input terminal is connected to the second output terminal of the AC input voltage source; the input inductor L g The output end of the switch tube Q 3 The source of the switch tube Q 4 The drain and resonant capacitor C r The left end of

[0010] The AC input voltage is connected in turn to the input inductor L g , low frequency bridge arm, high frequency bridge arm, bus capacitor C c , resonant capacitor C r , resonant inductor L r , transformer T, secondary bidirectional switch network, auxiliary capacitor C a 、Auxiliary capacitor C b , output filter capacitor C o And the output resistance R o ;

[0011] The switch tube Q 1 The drain of the switch tube Q 3 The drain of the switch tube Q 3 The source of the resonant capacitor C r The left end of the resonant capacitor C r The right end is connected to the resonant inductor L r The left end of the resonant inductor L r The right end is connected to the primary winding N of the transformer T p The same-name end of the transformer T primary winding N p The opposite terminal of the switch tube Q 1 The source of the switch tube Q 2 The drain of the switch tube Q 1 The source of the switch tube Q 2 The source of the switch tube Q 4 The source of the switch tube Q 4 The drain of the switch tube Q3 The source and input inductance L g The output terminal.

[0012] The bus capacitance C c The upper end is connected to the switch tube Q 3 The drain and bus capacitance C c The lower end of the switch tube is connected to Q 4 The source of

[0013] The secondary winding N of the transformer T s Connect the load R through the secondary bidirectional switch network o .

[0014] Preferably, the secondary bidirectional switch network includes a switch tube Q 5 ~Q 8 、Auxiliary capacitor C a 、Auxiliary capacitor C b , the secondary winding N of the transformer T s The same name terminal switch tube Q 5 and Q 7 The drain of the switch tube Q 5 The source of the switch tube Q 6 The source of the switch tube Q 6 The drain terminal is connected to the auxiliary capacitor C a The upper end and load R o , the auxiliary capacitor C a The lower end of the auxiliary capacitor C b The lower end and the secondary winding N of the transformer T s The synonym end of

[0015] The switch tube Q 7 The source of the switch tube Q 8 The source of the switch tube Q 8 The drain terminal is connected to the auxiliary capacitor C b The upper end and load R o , the auxiliary capacitor C b The lower end is connected to the secondary winding N of the transformer T s The secondary winding N s The same-name end of the LLC converter is used as the positive output end, and the secondary winding N s The opposite end of the pair serves as the negative output end of the LLC converter;

[0016] Preferably, the load R o There is also an output capacitor C in parallel at both ends of o The load R o is the output resistance, the switch tube Q 8 The drain terminal is connected to the output capacitor C oThe positive end of the switch tube Q 6 The drain terminal is connected to the resonant capacitor C o the negative terminal of the output resistor.

[0017] The present invention also provides a control method for a single-stage bridgeless AC-AC converter, which controls the single-stage bridgeless AC-AC converter by an external control circuit, comprising the following steps:

[0018] The control circuit is used to output a high-level switch tube Q during the positive half cycle of the AC input voltage. 1 , Q 6 and Q 7 The control signal output is always low level switch tube Q 2 The control signal of the switch tube Q is output as a complementary high-frequency square wave signal. 3 and Q 4 The control signal of the switch tube Q is output as a complementary high-frequency square wave signal. 5 and Q 8 The control signal of

[0019] The control circuit is used to output a high-level switch tube Q during the negative half cycle of the AC input voltage. 2 , Q 5 and Q 8 The control signal output is always low level switch tube Q 1 The control signal of the switch tube Q is output as a complementary high-frequency square wave signal. 3 and Q 4 The control signal of the switch tube Q is output as a complementary high-frequency square wave signal. 6 and Q 7 control signal;

[0020] Preferably, when there is no requirement for output voltage regulation, the switch tube Q output by the control circuit 3 ~Q 8 The control signal is a pulse signal with a fixed frequency in the high-frequency working range.

[0021] Preferably, when there is a requirement for output voltage regulation, the control circuit is used to dynamically adjust the output switch tube Q according to the output voltage and the resonant cavity current feedback signal. 3 ~Q 8 The frequency and duty cycle of the control signal in the high-frequency working range are used to adjust the amplitude of the AC output voltage.

[0022] The present invention also provides an application of a single-stage bridgeless AC-AC converter, comprising the following steps: adding a control circuit to the single-stage bridgeless AC-AC converter to obtain a single-stage bridgeless AC-AC converter device;

[0023] The load R of the single-stage bridgeless AC-AC converter in the single-stage bridgeless AC-AC converter device is o The two ends of are respectively used as output terminal one and output terminal two of a single-stage bridgeless AC-AC converter device;

[0024] The input inductance L of the single-stage bridgeless AC-AC converter in the single-stage bridgeless AC-AC converter device is g The input terminal and switch tube Q 1 The source electrodes are respectively used as the input terminal 1 and the input terminal 2 of the single-stage bridgeless AC-AC converter device;

[0025] Obtain three single-stage bridgeless AC-AC converter devices, named as device 1, device 2, and device 3 respectively;

[0026] Obtain a three-phase AC input power supply of a triangle structure consisting of three AC input voltage sources connected in series, where the three AC input voltage sources are denoted as Va, Vb, and Vc respectively;

[0027] Connecting input terminal 1 of device 1 and input terminal 2 of device 2 to form input terminal 12;

[0028] Connect the input terminal 1 of device 2 and the input terminal 2 of device 3 to form input terminal 23;

[0029] Connecting input terminal 1 of device 3 and input terminal 2 of device 1 to form input terminal 31;

[0030] Connecting output terminal 1 of device 1 and output terminal 2 of device 2 as output terminal 12;

[0031] Connecting the output terminal 1 of device 2 and the output terminal 2 of device 3 to form output terminal 23;

[0032] Connecting output terminal 1 of device 3 and output terminal 2 of device 1 to form output terminal 31;

[0033] Connect input terminal one and two to between Va and Vb, connect input terminal two and three to between Vb and Vc, and connect input terminal three and one to between Va and Vc;

[0034] A voltage signal Voa related to Va is output between output terminal 12 and output terminal 31; a voltage signal Vob related to Vb is output between output terminal 12 and output terminal 23; a voltage signal Voc related to Vc is output between output terminal 31 and output terminal 23.

[0035] The present invention also provides an application of a single-stage bridgeless AC-AC converter, comprising the following steps: adding a control circuit to the single-stage bridgeless AC-AC converter to obtain a single-stage bridgeless AC-AC converter device;

[0036] The load R of the single-stage bridgeless AC-AC converter in the single-stage bridgeless AC-AC converter device is o The two ends of are respectively used as output terminal one and output terminal two of a single-stage bridgeless AC-AC converter device;

[0037] The input inductance L of the single-stage bridgeless AC-AC converter in the single-stage bridgeless AC-AC converter device is g The input terminal and switch tube Q 1 The source electrodes are respectively used as the input terminal 1 and the input terminal 2 of the single-stage bridgeless AC-AC converter device;

[0038] Obtain three single-stage bridgeless AC-AC converter devices, named as device 1, device 2, and device 3 respectively;

[0039] Obtain a three-phase AC input power supply of a star structure consisting of three AC input voltage sources connected in parallel, the three AC input voltage sources are denoted as Va, Vb, and Vc respectively;

[0040] Connect the input terminal 1 of device 1, the input terminal 1 of device 2 and the input terminal 1 of device 3 to form a common point O;

[0041] Connect the output terminal 2 of device 1, the output terminal 2 of device 2 and the output terminal 2 of device 3 as a common point O';

[0042] Connect Va between input terminals 1 and 2 of device 1, connect Vb between input terminals 1 and 2 of device 2, and connect Vc between input terminals 1 and 2 of device 3;

[0043] A voltage signal Voa related to Va is output between the output terminal 1 and the output terminal 2 of the device 1; a voltage signal Vob related to Vb is output between the output terminal 1 and the output terminal 2 of the device 2; a voltage signal Voc related to Vc is output between the output terminal 1 and the output terminal 2 of the device 3;

[0044] Taking the positive half-cycle waveform of the grid-side AC as an example, the primary power-frequency tube Q 1 Conductivity, Q 2 Turn off, high frequency tube Q 3 , Q 4 Complementary conduction, when Q 3 On, Q 4 Shutdown, input inductor L g Stored energy, inductor current I lg Linear increase; when Q 3 Shutdown, Q 4 conduction, input inductance L g Release energy, inductor current I lg Gradually decreases. Bus capacitance Cc Working in boost state. High frequency transformer T excitation inductance L m The voltage at both ends is clamped by the secondary voltage, L r and C r In the resonant working state, energy is transferred from the primary side of the high-frequency transformer T to the secondary side. During this period, the switch tube Q 3 (or Q 4 ) Before turning on, the resonant cavity current presents a negative current, which makes the body diode conduct, turning on the switch tube Q 3 (or Q 4 ) The drain-source voltage is clamped to zero, and the switch tube Q is turned on. 3 , Q 4 ZVS can be achieved. The secondary switch tube Q 6 , Q 7 When in the on state, Q 5 and Q 8 Complementary conduction, a positive half-cycle waveform is obtained at both ends of the load. Similarly, when the AC half-cycle waveform is negative on the grid side, a negative half-cycle waveform is obtained at both ends of the load.

[0045] The present invention has the following characteristics and beneficial effects:

[0046] The invention scheme of the above-mentioned single-stage bridgeless AC-AC converter simplifies the complex circuit structure of the traditional AC-AC converter device, and has the advantages of fewer magnetic components, low circuit cost and simple control. At the same time, it also has the soft switching performance of the LLC resonant converter to achieve high efficiency and high power density, and is suitable for applications such as power electronic transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] 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 labor.

[0048] Figure 1 A structural diagram of a conventional power electronic transformer is shown;

[0049] Figure 2 A specific implementation example of the single-stage bridgeless AC-AC converter of the present invention is shown;

[0050] Figure 3 The main waveforms of the single-stage bridgeless AC-AC converter of the present invention are shown;

[0051] Figure 4An equivalent circuit diagram of the single-stage bridgeless AC-AC converter of the present invention in the positive half cycle of the AC input voltage is shown;

[0052] Figure 5 The single-stage bridgeless AC-AC converter of the present invention is shown in the positive half cycle of the AC input voltage, the switch tube Q 3 , Q 8 On, Q 4 , Q 5 Equivalent circuit diagram when turned off;

[0053] Figure 6 The single-stage bridgeless AC-AC converter of the present invention is shown in the positive half cycle of the AC input voltage, the switch tube Q 4 , Q 5 On, Q 3 , Q 8 Equivalent circuit diagram when turned off;

[0054] Figure 7 An equivalent circuit diagram of the single-stage bridgeless AC-AC converter of the present invention in the negative half cycle of the AC input voltage is shown;

[0055] Figure 8 The single-stage bridgeless AC-AC converter of the present invention is shown in the negative half cycle of the AC input voltage, the switch tube Q 3 , Q 6 On, Q 4 , Q 7 Equivalent circuit diagram when turned off;

[0056] Fig. 9 The single-stage bridgeless AC-AC converter of the present invention is shown in the negative half cycle of the AC input voltage, the switch tube Q 4 , Q 7 On, Q 3 , Q 6 Equivalent circuit diagram when turned off;

[0057] Fig.10 A connection diagram of a first three-phase AC-AC converter device formed by a single-stage bridgeless AC-AC converter according to the present invention is shown;

[0058] Fig.11 A connection diagram of a second three-phase AC-AC converter device formed by a single-stage bridgeless AC-AC converter according to the present invention is shown. DETAILED DESCRIPTION

[0059] It should be emphasized that the embodiments and features described in the present invention can be combined with each other under the premise that no contradiction occurs.

[0060] When describing the present invention, please note that directional or positional terms such as "upper", "lower", "front", "back", "left", "right", etc. are defined based on the orientation shown in the drawings, and are intended to simplify the description and facilitate understanding, rather than to limit the described devices or components to follow a specific spatial layout or operating direction. Therefore, these terms should not be understood as limitations on the present invention. Similarly, ordinal terms such as "first", "second", etc. are only used to distinguish and explain, and do not represent any order of importance or implicit quantitative limitation, that is, these features can be one or more.

[0061] When describing the present invention, the terms "access", "connection", "connection", etc., unless otherwise expressly specified or limited, should be understood as broad categories. This can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediary, or even the internal connection of two components. For those skilled in the art, the actual meaning of these terms in the present invention should be understood according to the specific context.

[0062] Example 1

[0063] The present invention provides a single-stage bridgeless AC-AC converter device, such as Figure 2 As shown, it includes: a specific implementation case of a single-stage bridgeless AC-AC converter and a control circuit.

[0064] The input inductance L g The input end is connected to the second output end of the AC input voltage source, and the input inductor L g The output end of the switch tube Q 3 The source of the switch tube Q 4 The drain and resonant capacitor C r The AC input voltage source is connected in turn to the input inductor L g , low frequency bridge arm, high frequency bridge arm, bus capacitor C c , resonant capacitor C r , resonant inductor L r , transformer T, secondary bidirectional switch network, auxiliary capacitor C a 、Auxiliary capacitor C b , output filter capacitor C o And the output resistance R o ;

[0065] The low-frequency bridge arm includes a switch tube Q 1 ~Q 2 The high frequency bridge arm includes a switch tube Q 3 ~Q 4 , the switch tube Q 1The drain of the switch tube Q 3 The drain of the switch tube Q 3 The source of the resonant capacitor C r The left end of the resonant capacitor C r The right end is connected to the resonant inductor L r The left end of the resonant inductor L r The right end is connected to the primary winding N of the transformer T p The primary winding N of the transformer T p The opposite terminal of the switch tube Q 1 The switch tube Q 2 The drain of the switch tube Q 1 The source of the switch tube Q 2 The source of the switch tube Q 4 The source of the switch tube Q 4 The drain of the switch tube Q 3 The source and input inductance L g The output terminal.

[0066] The bus capacitance C c The upper end is connected to the switch tube Q 3 The drain and bus capacitance C c The lower end of the switch tube is connected to Q 4 The source.

[0067] The secondary bidirectional switch network includes Q 5 ~Q 8 、Auxiliary capacitor C a 、Auxiliary capacitor C b , the secondary winding N of the transformer T s The same name terminal switch tube Q 5 and Q 7 The drain of the switch tube Q 5 The source of the switch tube Q 6 The source of the switch tube Q 6 The drain of the auxiliary capacitor Ca is connected to the upper end of the auxiliary capacitor C a The lower end is connected to the secondary winding N of the transformer T s The switch tube Q 7 The source of the switch tube Q 8 The source of the switch tube Q 8 The drain terminal is connected to the auxiliary capacitor C b The upper end of the auxiliary capacitor C b The lower end is connected to the secondary winding N of the transformer T s The transformer secondary winding N s The same-name end of the transformer is used as the positive output end of the LLC converter, and the secondary winding Ns The opposite end of the switch tube Q 8 The drain terminal is connected to the output capacitor C o The positive terminal and output resistor R o The positive terminal of the switch tube Q 6 The drain terminal is connected to the resonant capacitor C o The negative terminal and output resistor R o The negative terminal.

[0068] It can be understood that in the single-stage bridgeless AC-AC converter device of the present invention, the transformer T can be an integrated transformer, and the resonant inductor L r The leakage inductance of the transformer T can be used as a substitute, which is also a well-known technology in this professional field and will not be described in detail here.

[0069] Example 2

[0070] This embodiment provides a conversion method based on the single-stage bridgeless AC-AC converter device described in Embodiment 1, referring to Figure 3 The waveform diagram of the single-stage bridgeless AC-AC converter device of the present invention is shown.

[0071] The control circuit samples the AC input voltage to generate a switch tube Q 1 ~Q 8 The control signal is used to realize that the AC output current is a sine wave with the same frequency and phase as the AC input voltage. In the positive half cycle of the AC input voltage, the output is always high level switch tube Q 1 , Q 6 and Q 7 The control signal output is always low level switch tube Q 2 The output is a complementary high-frequency square wave signal of the switch tube Q 3 and Q 4 The control signal of the switch tube Q is the output of the complementary high-frequency square wave signal. 5 and Q 8 The control signal; in the negative half cycle of the AC input voltage, the output is always high level switch tube Q 2 , Q 5 and Q 8 The control signal output is always low level switch tube Q 1 The output is a complementary high-frequency square wave signal of the switch tube Q 3 and Q 4 The control signal of the switch tube Q is the output of the complementary high-frequency square wave signal. 6 and Q 7 control signal;

[0072] When there is no voltage regulation requirement, the switch tube Q output by the control circuit 3~Q 8 A fixed frequency pulse signal is received as a control instruction in the high frequency working range. When there is a voltage regulation requirement, the control circuit dynamically adjusts the switch tube Q according to the output voltage and the resonant cavity current feedback signal. 3 ~Q 8 The frequency and duty cycle of the control signal in the high-frequency working range are used to adjust the amplitude of the AC output voltage.

[0073] Example 3

[0074] This embodiment provides a specific implementation example of the single-stage bridgeless AC-AC converter device of the present invention, which works in the positive half cycle. Figure 4 As shown, including the input inductor L g , switch tube Q 3 , switch tube Q 4 , bus capacitance C c , resonant capacitor C r , resonant inductor L r , transformer T, switch tube Q 5 , switch tube Q 8 、Auxiliary capacitor C a 、Auxiliary capacitor C b , output filter capacitor C o And the output resistance R o Wherein, the input inductor L g The input end is connected to the second output end of the AC input voltage source, and the input inductor L g The output end of the switch tube Q 3 The source, Q 4 The drain and resonant capacitor C r The resonant capacitor C r The right end of the resonant inductor L r At the left end, the resonant inductor L r The right end is connected to the primary winding N of the transformer T p The primary winding N of the transformer T p The opposite-name terminal bus capacitor C c The upper end of the switch tube Q 3 The drain of the busbar capacitor C c The lower end is connected to the switch tube Q 4 The secondary winding N of the transformer T s The same name terminal switch tube Q 5 The drain and Q 8 The source of the switch tube Q 5 The source is connected to the auxiliary capacitor C a At the upper end, the capacitor C a The lower end is connected to the secondary winding N of the transformer Ts The switch tube Q 8 The drain terminal is connected to the auxiliary capacitor C b The upper end of the auxiliary capacitor C b The lower end is connected to the secondary winding N of the transformer T s The switch tube Q 8 The drain terminal is connected to the output capacitor C o The positive terminal and output resistor R o The positive terminal of the switch tube Q 5 The source of the resonant capacitor C o The negative terminal and output resistor R o When the switch tube Q 3 , Q 8 On, Q 4 , Q 5 When turned off, the equivalent circuit is as follows Figure 5 As shown, the transformer T excitation inductance L m Stored energy, excitation inductor current I Lm Linear increase; when the switch tube Q 4 , Q 5 On, Q 3 , Q 8 When turned off, the equivalent circuit is as follows Figure 6 As shown, the transformer T excitation inductance L m The stored energy is transferred through the secondary winding N of the transformer T. s Release to the load.

[0075] Example 4

[0076] This embodiment provides a specific implementation example of the single-stage bridgeless AC-AC converter device of the present invention, which works in the negative half cycle. Figure 7 As shown, including the input inductor L g , switch tube Q 3 , switch tube Q 4 , bus capacitance C c , resonant capacitor C r , resonant inductor L r , transformer T, switch tube Q 6 , switch tube Q 7 、Auxiliary capacitor C a 、Auxiliary capacitor C b , output filter capacitor C o And the output resistance R o Wherein, the input inductor L g The input end is connected to the second output end of the AC input voltage, and the input inductor L g The output end of the switch tube Q 3 The source, Q 4The drain and resonant capacitor C r The resonant capacitor C r The right end of the resonant inductor L r At the left end, the resonant inductor L r The right end is connected to the primary winding N of the transformer T p The primary winding N of the transformer T is connected to the same terminal. p The opposite-name terminal bus capacitor C c The upper end of the switch tube Q 4 The bus capacitor C c The lower end is connected to the switch tube Q 3 The secondary winding N of the transformer T s The same name terminal switch tube Q 6 source and Q 7 The drain of the switch tube Q 6 The drain terminal is connected to the auxiliary capacitor C a At the upper end, the capacitor C a The lower end is connected to the secondary winding N of the transformer T s The switch tube Q 7 The source is connected to the auxiliary capacitor C b The upper end of the auxiliary capacitor C b The lower end is connected to the secondary winding N of the transformer T s The switch tube Q 7 The source of the output capacitor C o The positive terminal and output resistor R o The positive terminal of the switch tube Q 6 The drain terminal is connected to the resonant capacitor C o The negative terminal and output resistor R o When the switch tube Q 3 , Q 6 On, Q 4 , Q 7 When turned off, the equivalent circuit is as follows Figure 8 As shown, the transformer T excitation inductance L m Stored energy, excitation inductor current I Lm Linear increase; when the switch tube Q 4 , Q 7 On, Q 3 , Q 6 When turned off, the equivalent circuit is as follows Fig. 9 As shown, the transformer T excitation inductance L m The stored energy is transferred through the secondary winding N of the transformer T. s Release to the load.

[0077] Example 5

[0078] This embodiment provides an application example of a single-stage bridgeless AC-AC converter device, such as Fig.10 As shown in the figure, in this application, the three-phase AC input power adopts a delta Δ connection method, which can provide balanced current distribution, enhance the stability of the power system and reduce the generation of harmonics. The main body of the device includes three AC-AC converter devices. The output voltage also adopts a delta Δ connection method, which helps to improve the stability and quality of the output voltage, which is crucial to ensure the normal operation of the equipment and extend its service life.

[0079] Example 6

[0080] This embodiment provides an application example of a single-stage bridgeless AC-AC converter device, such as Fig.11 As shown, in this application, the three-phase AC input power adopts a star Y connection method, which connects the starting ends of the three-phase power together to form a common point O, and leads three phase lines from the end of each phase and connects them together to form a common point O'. This connection method maintains the same connection characteristics as the input power supply, ensures the stability and balance of the output voltage and the balanced distribution of current among the three phases. By introducing the neutral line, it provides additional grounding protection for the system, enhancing the safety and stability of the power system.

[0081] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments including components are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A single-stage bridgeless AC-AC converter, characterized in that: include: Input inductance L g , low frequency bridge arm, high frequency bridge arm, bus capacitor C c , resonant capacitor C r , resonant inductor L r , transformer T, secondary bidirectional switch network, output filter capacitor C o and load R o ; The low-frequency bridge arm includes a switch tube Q1 and a switch tube Q2, and the high-frequency bridge arm includes a switch tube Q3 and a switch tube Q4; The AC input voltage source includes a first and a second output terminal, the input inductor L g The input terminal is connected to the second output terminal of the AC input voltage source; the input inductor L g The output end is connected to the source of the switch tube Q3, the drain of the switch tube Q4 and the resonant capacitor C r The left end of The drain of the switch tube Q1 is connected to the drain of the switch tube Q3, and the resonant capacitor C r The right end is connected to the resonant inductor L r The left end of the resonant inductor L r The right end is connected to the primary winding N of the transformer T p The same-name end of the transformer T primary winding N p The opposite end is connected to the source of the switch tube Q1 and the first output end of the AC input voltage source; the drain of the switch tube Q2 is connected to the source of the switch tube Q1, the source of the switch tube Q2 is connected to the source of the switch tube Q4, and the bus capacitor C c The upper end is connected to the drain of the switch tube Q3, and the bus capacitor C c The lower end is connected to the source of the switch tube Q4; The secondary winding N of the transformer T s Connect the load R through the secondary bidirectional switch network o .

2. A single-stage bridgeless AC-AC converter as claimed in claim 1, characterized in that: The secondary bidirectional switch network includes switch tubes Q5-Q8, auxiliary capacitor C a 、Auxiliary capacitor C b , the secondary winding N of the transformer T s The same-name terminal is connected to the drain of the switch tubes Q5 and Q7, the source of the switch tube Q5 is connected to the source of the switch tube Q6, and the drain of the switch tube Q6 is connected to the auxiliary capacitor C a The upper end and load R o , the auxiliary capacitor C a The lower end of the auxiliary capacitor C b The lower end and the secondary winding N of the transformer T s The synonym end of The source of the switch tube Q7 is connected to the source of the switch tube Q8, and the drain of the switch tube Q8 is connected to the auxiliary capacitor C b The upper end and load R o .

3. A single-stage bridgeless AC-AC converter as claimed in claim 2, characterized in that: The load R o There is also an output capacitor C in parallel at both ends of o .

4. A control method for a single-stage bridgeless AC-AC converter as claimed in claim 3, characterized in that: The single-stage bridgeless AC-AC converter is controlled by an external control circuit, including the following steps: The control circuit is used to output control signals of the switch tubes Q1, Q6 and Q7 which are constantly at a high level, output control signals of the switch tube Q2 which are constantly at a low level, output control signals of the switch tubes Q3 and Q4 which are complementary high-frequency square wave signals, and output control signals of the switch tubes Q5 and Q8 which are complementary high-frequency square wave signals in the positive half cycle of the AC input voltage; The control circuit is used to output control signals of switch tubes Q2, Q5 and Q8 that are constantly at a high level, output control signals of switch tube Q1 that are constantly at a low level, output control signals of switch tubes Q3 and Q4 that are complementary high-frequency square wave signals, and output control signals of switch tubes Q6 and Q7 that are complementary high-frequency square wave signals during the negative half cycle of the AC input voltage.

5. A control method for a single-stage bridgeless AC-AC converter as claimed in claim 4, characterized in that: When there is no requirement for output voltage regulation, the control signals of the switch tubes Q3 to Q8 output by the control circuit are pulse signals with a fixed frequency in the high-frequency working range.

6. A control method for a single-stage bridgeless AC-AC converter as claimed in claim 5, characterized in that: When there is a requirement for output voltage regulation, the control circuit is used to dynamically adjust the frequency and duty cycle of the control signals of the output switching tubes Q3 to Q8 in the high-frequency working range according to the output voltage and the resonant cavity current feedback signal, so as to adjust the amplitude of the AC output voltage.

7. The use of a single-stage bridgeless AC-AC converter as claimed in claim 3, characterized in that: The following steps are involved: A control circuit is added to the single-stage bridgeless AC-AC converter to obtain a single-stage bridgeless AC-AC converter device; a load R of the single-stage bridgeless AC-AC converter in the single-stage bridgeless AC-AC converter device is set o The two ends of are respectively used as output terminal one and output terminal two of a single-stage bridgeless AC-AC converter device; The input inductance L of the single-stage bridgeless AC-AC converter in the single-stage bridgeless AC-AC converter device is g The input terminal of and the source electrode of the switch tube Q1 are respectively used as the input terminal 1 and the input terminal 2 of the single-stage bridgeless AC-AC converter device; Obtain three single-stage bridgeless AC-AC converter devices, named as device 1, device 2, and device 3 respectively; Obtain a three-phase AC input power supply of a triangle structure consisting of three AC input voltage sources connected in series, where the three AC input voltage sources are denoted as Va, Vb, and Vc respectively; Connecting input terminal 1 of device 1 and input terminal 2 of device 2 to form input terminal 12; Connect the input terminal 1 of device 2 and the input terminal 2 of device 3 to form input terminal 23; Connecting input terminal 1 of device 3 and input terminal 2 of device 1 to form input terminal 31; Connecting output terminal 1 of device 1 and output terminal 2 of device 2 as output terminal 12; Connecting the output terminal 1 of device 2 and the output terminal 2 of device 3 to form output terminal 23; Connecting output terminal 1 of device 3 and output terminal 2 of device 1 to form output terminal 31; Connect input terminal one and two between Va and Vb, connect input terminal two and three between Vb and Vc, and connect input terminal three and one between Va and Vc; A voltage signal Voa related to Va is output between output terminal 12 and output terminal 31; a voltage signal Vob related to Vb is output between output terminal 12 and output terminal 23; a voltage signal Voc related to Vc is output between output terminal 31 and output terminal 23.

8. The use of a single-stage bridgeless AC-AC converter as claimed in claim 3, characterized in that: The following steps are involved: A control circuit is added to the single-stage bridgeless AC-AC converter to obtain a single-stage bridgeless AC-AC converter device; a load R of the single-stage bridgeless AC-AC converter in the single-stage bridgeless AC-AC converter device is set o The two ends of are respectively used as output terminal one and output terminal two of a single-stage bridgeless AC-AC converter device; The input inductance L of the single-stage bridgeless AC-AC converter in the single-stage bridgeless AC-AC converter device is g The input terminal of and the source electrode of the switch tube Q1 are respectively used as the input terminal 1 and the input terminal 2 of the single-stage bridgeless AC-AC converter device; Obtain three single-stage bridgeless AC-AC converter devices, named as device 1, device 2, and device 3 respectively; Obtain a three-phase AC input power supply of a star structure consisting of three AC input voltage sources connected in parallel, and the three AC input voltage sources are denoted as Va, Vb, and Vc respectively; Connect the input terminal 1 of device 1, the input terminal 1 of device 2 and the input terminal 1 of device 3 to form a common point O; Connect the output terminal 2 of device 1, the output terminal 2 of device 2 and the output terminal 2 of device 3 as a common point O'; Va is connected between input terminal 1 and input terminal 2 of device 1, Vb is connected between input terminal 1 and input terminal 2 of device 2, and Vc is connected between input terminal 1 and input terminal 2 of device 3; a voltage signal Voa related to Va is output between output terminal 1 and output terminal 2 of device 1; a voltage signal Vob related to Vb is output between output terminal 1 and output terminal 2 of device 2; a voltage signal Voc related to Vc is output between output terminal 1 and output terminal 2 of device 3.

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