A bidirectional high-frequency isolated AC-DC converter

Abstract

This invention provides a bidirectional high-frequency isolated AC / DC converter, relating to the field of converter technology. This application discloses a single-phase bidirectional high-frequency isolated AC / DC converter and a three-phase bidirectional high-frequency isolated AC / DC converter. The three-phase bidirectional high-frequency isolated AC / DC converter comprises three modular single-phase bidirectional high-frequency isolated AC / DC converters. Each single-phase bidirectional high-frequency isolated AC / DC converter includes an H4 bridge, a first inductor, a second inductor, a first intermediate capacitor, a second intermediate capacitor, a transformer, and a fifth switch. Each arm of the H4 bridge includes one switch. All five switches have three operating states: conduction from the first terminal to the second terminal, conduction from the second terminal to the first terminal, and disconnection. This invention achieves a bidirectional isolated AC / DC converter through a single-stage energy conversion, using fewer components, fewer sampling circuits, resulting in lower equipment cost and smaller size.

Description

Technical Field

[0001] This invention relates to the field of converter technology, and specifically to a bidirectional high-frequency isolated AC / DC converter. Background Technology

[0002] A bidirectional AC-DC converter (also known as a bidirectional inverter or bidirectional converter) is a power electronic device capable of bidirectional energy conversion between alternating current (AC) and direct current (DC) as needed. Its core value lies in enabling reversible energy flow, which has become crucial in the context of increasingly complex modern energy systems and ever-higher demands for energy management and efficiency.

[0003] Currently, bidirectional AC-DC converters are mainly two-stage, with a non-isolated AC-DC converter on the AC side and an isolated DC-DC converter on the DC side, enabling bidirectional energy flow. Figure 1 As shown.

[0004] However, existing bidirectional AC-DC converters require two stages of energy conversion, resulting in low efficiency. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a bidirectional high-frequency isolated AC / DC converter, which solves the technical problem that existing bidirectional AC / DC converters require two stages of energy conversion.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] In a first aspect, the present invention provides a single-phase bidirectional high-frequency isolated AC / DC converter, comprising an H4 bridge, a first inductor, a second inductor, a first intermediate capacitor, a second intermediate capacitor, a transformer, and a fifth switch;

[0010] The H4 bridge includes four bridge arms, each of which includes a switch. The common terminal of the third switch and the first switch serves as the second connection terminal of the H4 bridge; the common terminal of the third switch and the fourth switch serves as the first connection terminal of the H4 bridge; the common terminal of the first switch and the second switch serves as the third connection terminal of the H4 bridge; and the common terminal of the fourth switch and the second switch serves as the fourth connection terminal of the H4 bridge.

[0011] Specifically, the first connection terminal of the H4 bridge is connected to the first port of the converter via the first inductor; the third connection terminal of the H4 bridge is connected to the second port of the converter; the second connection terminal of the H4 bridge is connected to the first end of the first side of the transformer via the first intermediate capacitor; and the fourth connection terminal of the H4 bridge is connected to the second end of the first side of the transformer.

[0012] The first terminal of the second side of the transformer is connected to the third port of the converter; the second terminal of the second side of the transformer is connected to the fourth port of the converter via the second intermediate capacitor and the second inductor; the common terminal of the second intermediate capacitor and the second inductor is connected to the first terminal of the second side of the transformer via the fifth switch.

[0013] The third terminal of each of the five switches is a control terminal, which is suitable for controlling the working state of the five switches under the control of the control signal connected to the control terminal, so that the converter is in rectification mode or inverter mode. Each of the five switches has three working states: conduction from the first terminal to the second terminal, conduction from the second terminal to the first terminal, and disconnection.

[0014] Preferably, the transformer is a two-ended transformer.

[0015] Preferably, the switches in each arm of the H4 bridge include switching transistors with reverse parallel freewheeling diodes.

[0016] Preferably, the fifth switch includes a switching transistor with a reverse-parallel freewheeling diode;

[0017] The switching mode of the reverse parallel freewheeling diode includes: the anode of the freewheeling diode is connected to the common terminal of the second intermediate capacitor and the second inductor; or the cathode of the diode is connected to the common terminal of the second intermediate capacitor and the second inductor.

[0018] In a second aspect, the present invention provides a three-phase bidirectional high-frequency isolated AC / DC converter, comprising three single-phase bidirectional high-frequency isolated AC / DC converters, each single-phase bidirectional high-frequency isolated AC / DC converter comprising an H4 bridge, a first inductor, a first intermediate capacitor, a second intermediate capacitor, a transformer, a second inductor, and a fifth switch;

[0019] The H4 bridge includes four bridge arms, each of which includes a switch. The common terminal of the third switch and the first switch serves as the second connection terminal of the H4 bridge; the common terminal of the third switch and the fourth switch serves as the first connection terminal of the H4 bridge; the common terminal of the first switch and the second switch serves as the third connection terminal of the H4 bridge; and the common terminal of the fourth switch and the second switch serves as the fourth connection terminal of the H4 bridge.

[0020] Specifically, the first connection terminal of the H4 bridge is connected to the first port of the converter via the first inductor; the third connection terminal of the H4 bridge is connected to the second port of the converter; the second connection terminal of the H4 bridge is connected to the first end of the first side of the transformer via the first intermediate capacitor; and the fourth connection terminal of the H4 bridge is connected to the second end of the first side of the transformer.

[0021] The first terminal of the second side of the transformer is connected to the third port of the converter; the second terminal of the second side of the transformer is connected to the fourth port of the converter via the second intermediate capacitor and the second inductor; the common terminal of the second intermediate capacitor and the second inductor is connected to the first terminal of the second side of the transformer via the fifth switch.

[0022] The third ports of three single-phase bidirectional high-frequency isolated AC / DC converters are connected together as the third port of the three-phase bidirectional high-frequency isolated AC / DC converter, and the fourth ports of three single-phase bidirectional high-frequency isolated AC / DC converters are connected together as the fourth port of the three-phase bidirectional high-frequency isolated AC / DC converter.

[0023] The second ports of the three single-phase bidirectional high-frequency isolated AC-DC converters are connected together, and the first ports of the three single-phase bidirectional high-frequency isolated AC-DC converters are respectively used as the A, B, and C three-phase ports;

[0024] The third terminal of each of the fifteen switches is a control terminal, which is suitable for controlling the working state of the fifteen switches under the control of the control signal connected to the control terminal, so that the converter is in rectification mode or inverter mode. Each of the fifteen switches has three working states: conduction from the first terminal to the second terminal, conduction from the second terminal to the first terminal, and disconnection.

[0025] Preferably, the transformer is a two-ended transformer.

[0026] Preferably, the switches in each arm of the H4 bridge include switching transistors with reverse parallel freewheeling diodes.

[0027] Preferably, the fifth switch includes a switching transistor with a reverse-parallel freewheeling diode;

[0028] The switching mode of the reverse parallel freewheeling diode includes: the anode of the freewheeling diode is connected to the common terminal of the second intermediate capacitor and the second inductor; or the cathode of the diode is connected to the common terminal of the second intermediate capacitor and the second inductor.

[0029] Preferably, the second ports of the three single-phase bidirectional high-frequency isolated AC / DC converters are connected together, and their common terminal is grounded;

[0030] In rectification mode, the A, B, and C phase ports are connected to the first terminals of the three-phase power supply, and the second terminals of the three-phase power supply are connected together and then grounded; in inverter mode, the A, B, and C phase ports are connected to the first terminals of the three loads, and the second terminals of the three loads are connected together and then grounded.

[0031] The grounding terminal serves as the neutral (N) line in a three-phase four-wire system.

[0032] Preferably, the three single-phase bidirectional high-frequency isolated AC / DC converters are all modularly designed, with each phase controlled independently.

[0033] (III) Beneficial Effects

[0034] This invention provides a bidirectional high-frequency isolated AC / DC converter. Compared with the prior art, it has the following advantages:

[0035] This invention employs a single-stage energy conversion to achieve a bidirectional isolated AC-DC converter, requiring fewer components and sampling circuits, resulting in lower equipment cost and smaller size. Simultaneously, the single-stage energy conversion improves operating efficiency. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is the first existing single-phase two-stage bidirectional AC-DC converter;

[0038] Figure 2 This is the second type of existing single-phase two-stage bidirectional AC-DC converter;

[0039] Figure 3 For existing three-phase two-stage bidirectional AC-DC converters;

[0040] Figure 4 The circuit diagram of the single-phase bidirectional high-frequency isolated AC / DC converter in Example 1 is shown below.

[0041] Figure 5 for Figure 4 The circuit diagram shown is the first specific circuit diagram of the circuit framework diagram;

[0042] Figure 6 for Figure 4 The second specific circuit diagram shown in the circuit framework diagram;

[0043] Figure 7 for Figure 5 The circuit diagram shown is a basic topology diagram in rectification mode;

[0044] Figure 8 for Figure 7 The circuit diagram shown is a schematic diagram of operating mode 1a when the input voltage is greater than zero;

[0045] Figure 9 for Figure 7 The circuit diagram shown is a schematic diagram of operating mode 2a when the input voltage is greater than zero;

[0046] Figure 10 for Figure 7 The circuit diagram shown is a schematic diagram of operating mode 3a when the input voltage is greater than zero;

[0047] Figure 11 for Figure 7 The circuit diagram shown is a schematic diagram of operating mode 1b when the input voltage is less than zero;

[0048] Figure 12 for Figure 7 The circuit diagram shown is a schematic diagram of operating mode 2b when the input voltage is less than zero;

[0049] Figure 13 for Figure 7 The circuit diagram shown is a schematic diagram of operating mode 3b when the input voltage is less than zero;

[0050] Figure 14 for Figure 6 The circuit diagram shown is a basic topology diagram in inverter mode;

[0051] Figure 15 for Figure 14 The circuit diagram shown is a schematic diagram of the first operating mode.

[0052] Figure 16 for Figure 14 The circuit diagram shown is a schematic diagram of the second operating mode.

[0053] Figure 17 for Figure 14 The circuit diagram shown is a schematic diagram of the third working mode.

[0054] Figure 18 for Figure 14 The circuit diagram shown is a schematic diagram of the fourth operating mode.

[0055] Figure 19 This is the first circuit diagram of the three-phase bidirectional high-frequency isolated AC / DC converter in Example 2;

[0056] Figure 20This is the second circuit diagram of the three-phase bidirectional high-frequency isolated AC / DC converter in Example 2;

[0057] Figure 21 This is the third circuit diagram of the three-phase bidirectional high-frequency isolated AC / DC converter in Example 2;

[0058] Figure 22 This is the fourth circuit diagram of the three-phase bidirectional high-frequency isolated AC / DC converter in Example 2. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] It should be noted that, for ease of description, the IGBT is used to represent the controllable (on and off) switching transistor in the embodiments of this invention, but the switching transistor in this invention is not limited to IGBT. An IGBT will be used as an example. The first terminal of an IGBT refers to the collector, the second terminal to the emitter, and the control terminal to the gate. A drive control signal is applied to the control terminal of each switching transistor in the embodiments of this invention. For simplicity, this will not be elaborated further. The power switching transistor in the embodiments of this invention can also be implemented using other controllable switching transistor devices besides IGBT, such as MOSFET.

[0061] This application provides a bidirectional high-frequency isolated AC / DC converter, which solves the technical problem that existing bidirectional AC / DC converters require two stages of energy conversion, achieving single-stage energy conversion and improving the converter's operating efficiency.

[0062] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows:

[0063] The widespread application of bidirectional AC-CDC converters stems primarily from the following key requirements and technological trends:

[0064] 1. Renewable Energy (PV, Wind Power) Grid Connection and Consumption: Solar PV panels output DC power, while wind turbines (typically) output AC power, but the frequency / voltage is unstable. This needs to be converted to grid-compatible AC power before grid connection. Under certain circumstances (such as grid failures or dispatch requirements), the system may need to feed energy back from the grid to the DC bus (e.g., to charge energy storage batteries) or quickly disconnect from the grid (islanding operation). In these situations, the ability to reverse energy flow is required, and bidirectional AC-DC converters are key to achieving this flexible control.

[0065] 2. Core Interface of Energy Storage Systems: Mainstream energy storage technologies such as batteries and supercapacitors operate on the DC side. To connect them to the AC grid, supply power to AC loads, or absorb energy from the grid / other AC sources for charging, AC / DC conversion is necessary.

[0066] 3. Microgrids and Off-Grid Systems: Microgrids (grid-connected or off-grid) typically include various distributed energy sources (solar, wind), energy storage systems, and loads. The system needs to operate stably under different operating modes (grid-connected, islanded) and optimize internal energy flow. Grid-connected mode: Excess energy (from renewable energy or energy storage) can be fed back into the grid, or power can be drawn from the grid to charge or supplement energy storage. Islanded mode: Energy storage supplies power to AC loads via bidirectional AC-DC converters. If there are AC sources such as diesel generators in the system, they can also be used to charge the energy storage.

[0067] 4. Electric Vehicle Charging Infrastructure: An electric vehicle is essentially a large mobile energy storage unit. Vehicle-to-grid and vehicle-to-everything technologies allow electric vehicles not only to charge from the grid but also to feed battery energy back to the grid when needed (such as during peak loads or frequency regulation) or to power other DC / AC loads (such as homes or other vehicles). Bidirectional AC / DC charging stations are key equipment for enabling this bidirectional energy exchange.

[0068] 5. Uninterruptible Power Supply (UPS): When the power grid is normal, the UPS charges the battery via a rectifier and simultaneously supplies power to the load via an inverter (usually online). In the event of a power grid failure, the battery immediately supplies power through the inverter. Modern high-efficiency UPS systems (especially those with ECO mode or active filtering) increasingly use bidirectional converters as rectifier / inverter units. The same set of power devices and topology operate as a rectifier when the power grid is normal, and seamlessly switch to inverter mode during power grid failures.

[0069] 6. Regenerative Braking Energy Recovery (Rail Transit, Elevators, Industrial Motors): Motors generate regenerative energy (kinetic / potential energy converted into electrical energy) during braking. In AC power supply systems (such as subways and factories using AC buses), the front-end converter in the motor driver needs to be able to convert the AC energy fed back from the motor (which is equivalent to a generator) into DC, feeding it back to the DC bus for use by other loads or to charge energy storage devices, rather than consuming it in the braking resistor. This requires the front-end converter to have bidirectional operation capability (rectification and inverter mode switching).

[0070] Existing commonly used bidirectional AC-DC converters, such as Figures 1-3 As shown, where, Figure 1 , Figure 2 All of them are common single-phase two-stage bidirectional AC-DC converters. Figure 3This is a three-phase, two-stage, bidirectional AC-CDC converter. Existing bidirectional AC-CDC converters mainly suffer from the following drawbacks:

[0071] 1. The two-stage energy conversion system consists of a bidirectional AC-DC circuit and a bidirectional isolated DC / DC converter. The two-stage energy conversion system uses a large number of components and requires more sampling circuits, resulting in relatively high cost and larger equipment size.

[0072] 2. Two-stage energy conversion requires AC-DC-DC conversion, which results in low efficiency;

[0073] 3. A suitable bus capacitor needs to be set at the output of the preamplifier, as bus capacitors have a lifespan issue.

[0074] in addition, Figure 2 The transformer in the single-phase, single-stage, bidirectional AC-CDC converter shown is a single-ended transformer, which has problems such as leakage inductance.

[0075] To overcome the above problems, this invention proposes a bidirectional high-frequency isolated AC-DC converter. This converter achieves bidirectional isolation through a single-stage energy conversion, improving operating efficiency. Furthermore, it uses fewer components and has fewer sampling circuits, resulting in lower equipment cost and smaller size. Additionally, this converter eliminates the need for a bus capacitor, thus avoiding the lifespan issues associated with bus capacitors.

[0076] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0077] Example 1:

[0078] This embodiment proposes a single-phase bidirectional high-frequency isolated AC / DC converter, such as... Figure 4 As shown, it includes an H4 bridge, a first inductor L1, a first intermediate capacitor C1, a second intermediate capacitor C2, a transformer, a second inductor L2, and a fifth switch.

[0079] The H4 bridge includes four bridge arms, each of which includes a switch. The common terminal of the third switch and the first switch serves as the second connection terminal of the H4 bridge; the common terminal of the third switch and the fourth switch serves as the first connection terminal of the H4 bridge; the common terminal of the first switch and the second switch serves as the third connection terminal of the H4 bridge; and the common terminal of the fourth switch and the second switch serves as the fourth connection terminal of the H4 bridge.

[0080] Specifically, the first connection terminal of the H4 bridge is connected to the first port of the converter via the first inductor L1; the third connection terminal of the H4 bridge is connected to the second port of the converter; the second connection terminal of the H4 bridge is connected to the first end of the first side of the transformer via the first intermediate capacitor C1; and the fourth connection terminal of the H4 bridge is connected to the second end of the first side of the transformer.

[0081] The first terminal of the second side of the transformer is connected to the third port of the converter; the second terminal of the second side of the transformer is connected to the fourth port of the converter via the second intermediate capacitor C2 and the second inductor L2; the common terminal of the second intermediate capacitor C2 and the second inductor L2 is connected to the first terminal of the second side of the transformer via the fifth switch.

[0082] The third terminal of each of the five switches is a control terminal, which is suitable for controlling the working state of the five switches under the control of the control signal connected to the control terminal, so that the converter is in rectification mode or inverter mode. Each of the five switches has three working states: conduction from the first terminal to the second terminal, conduction from the second terminal to the first terminal, and disconnection.

[0083] In rectification mode, the first and second ports of the converter are connected to the two ends of the AC power supply, and the third and fourth ports are connected to the two ends of the load (in this embodiment, the load is an RC load).

[0084] In inverter mode, the first and second ports of the converter are connected to the load terminals, and the third and fourth ports are connected to the DC power supply terminals.

[0085] The transformer in this embodiment is a double-ended transformer. In a double-ended transformer, energy transfer is achieved through bidirectional current drive, without relying entirely on the magnetic core to store energy. Therefore, the air gap can be designed to be extremely small, thereby effectively reducing the transformer size and reducing the impact of parasitic parameters such as leakage inductance.

[0086] In practical implementation, all five switches can be switching transistors with reverse parallel freewheeling diodes, such as IGBTs or MOSFETs with reverse parallel freewheeling diodes. Alternatively, other devices capable of achieving the three operating states described above, such as bidirectional thyristors, can also be used. In this embodiment, an IGBT with reverse parallel diodes is taken as an example. In this embodiment of the invention, the five switching transistors are represented by S1, S2, S3, S4, and S5, respectively, and their corresponding reverse parallel diodes are represented by D1, D2, D3, D4, and D5, respectively.

[0087] In practical implementation, the fifth switch has two connection methods, such as... Figure 5 As shown, the emitter of the switching transistor (corresponding to the anode of the diode) is connected to the common terminal of the second intermediate capacitor C2 and the second inductor L2, and the collector of the switching transistor (corresponding to the cathode of the diode) is connected to the first terminal of the second side of the transformer. Another connection method is as follows... Figure 6As shown, the collector of the switching transistor (corresponding to the cathode of the diode) is connected to the common terminal of the second intermediate capacitor C2 and the second inductor L2, and the emitter of the switching transistor (corresponding to the anode of the diode) is connected to the second terminal of the second side of the transformer. The difference between the two variations lies in whether the second intermediate capacitor C2 and the second inductor L2 are connected to the third or fourth port of the transformer.

[0088] The following is based on Figure 5 Taking a single-phase bidirectional high-frequency isolated AC / DC converter as an example, modal analysis is performed:

[0089] The basic topology of the rectification mode is as follows Figure 7 As shown, in rectification mode, the switching transistors in the third, fourth, and fifth switches are all off and inactive (it should be noted that each switching transistor has a built-in anti-parallel diode, but for ease of description, in modal analysis, "switching off" refers to turning off the transistor within the switching transistor; whether the diode is conducting or cut off will be explained separately in modal analysis. Similarly, "switching on" refers to the transistor conducting), and the anti-parallel diodes are operational. In this mode, the first inductor L1 is the input inductor, the second inductor L2 is the output inductor, the first side of the transformer is the primary side, and the second side is the secondary side. In rectification mode, a single-phase bidirectional high-frequency isolated AC / DC converter can operate in continuous current mode and discontinuous current mode, which will be described in detail below:

[0090] When the input voltage is greater than zero, the current continuous mode is changed from Figure 8 and Figure 9 Composition, the discontinuous current mode is mainly composed of Figure 8 , Figure 9 and Figure 10 composition.

[0091] Working mode 1a, such as Figure 8 As shown, switches S1 and S2 are simultaneously turned on, and the power supply charges the first inductor L1 through diode D3 in the third switch and switch S1; the two intermediate capacitors charge the load and the second inductor L2 through switches S1 and S2 and the transformer. The transformer charges and discharges simultaneously, and does not have the function of energy storage.

[0092] Working mode 2a, such as Figure 9 As shown, when switches S1 and S2 are simultaneously turned off, the first inductor L1 freewheels through diode D3, diode D2, the transformer, and the two intermediate capacitors. The second inductor L2 freewheels through diode D5 and the load. It can be seen that switch S2 is turned on with zero voltage.

[0093] Working mode 3a, such as Figure 10As shown, compared to operating mode 2a, there is no change in the current flow direction on the primary and secondary sides of the transformer, but the current in the second inductor L2 enters discontinuous mode, and the load continues to be powered by the filter capacitor. The continuous current mode is... Figure 8 and Figure 9 Composition, the discontinuous current mode is mainly composed of Figure 8 , Figure 9 and Figure 10 composition.

[0094] When the input voltage is less than zero, the current continuous mode is changed from Figure 11 and Figure 12 Composition, the discontinuous current mode is mainly composed of Figure 11 , Figure 12 and Figure 13 composition.

[0095] Working mode 1b, such as Figure 11 As shown, switches S1 and S2 are simultaneously turned on. Power is supplied to the first inductor L1 via diode D4 and switch S2. The two intermediate capacitors charge the load and the second inductor L2 via switches S1 and S2 and the transformer. The transformer is simultaneously charging and discharging; therefore, the transformer does not have an energy storage function.

[0096] Working mode 2b, such as Figure 12 As shown, when switches S1 and S2 are simultaneously turned off, the first inductor L1 freewheels through the anti-parallel diode D1 of switch S1, the transformer, diode D4, and the two intermediate capacitors. The second inductor L2 freewheels through the anti-parallel diode D5 of the fifth switch and the load. It can be seen that switch S1 is turned on with zero voltage.

[0097] Working mode 3b, such as Figure 13 As shown, compared to operating mode 2b, the current flow direction on the primary and secondary sides of the transformer does not change, but the current in the second inductor L2 enters discontinuous mode, and the load is continued to be powered by the filter capacitor. The continuous current mode is... Figure 11 and Figure 12 Composition, the discontinuous current mode is mainly composed of Figure 11 , Figure 12 and Figure 13 composition.

[0098] by Figure 6 Taking the converter as an example, the basic topology of the inverter mode is as follows: Figure 14 As shown, in this mode, the first inductor L1 is the output inductor, the second inductor L2 is the input inductor, the first side of the transformer is the secondary side, and the second side is the primary side. This topology mainly consists of four modes: when the output voltage is positive, it is operating modes one and two; when the output voltage is negative, it is operating modes three and four.

[0099] Working mode as Figure 15As shown, when switches S5, S3, and S2 are turned on, the input voltage charges the first inductor L1 through switch S5, and the intermediate capacitor charges the first inductor L1 through the transformer and switches S3 and S2.

[0100] Working mode two such as Figure 16 As shown, only S3 is conducting. The second inductor L2 freewheels through the capacitor, the transformer, and the anti-parallel diodes D1 and D2 of switches S1 and S2. The first inductor L1 freewheels through the anti-parallel diodes D1 and S3 of switch S1. It can be seen that when transitioning from operating mode one to operating mode two, the current flowing through switch S1 is through its anti-parallel diodes, and the voltage drop is approximately zero. Therefore, S1 is turned on at zero voltage.

[0101] Working Mode Three Figure 17 As shown, switches S5, S1, and S4 are turned on. The input voltage charges the second inductor L2 through switch S5, and the intermediate capacitor charges the first inductor L1 through the transformer and switches S1 and S4.

[0102] Working Mode Four Figure 18 As shown, only switch S4 is conducting. The second inductor L2 freewheels through the capacitor, the transformer, and the anti-parallel diodes of switches S1 and S2. The first inductor L1 freewheels through the anti-parallel diode of switch S2 and S4. It can be seen that switch S1 is turned on with zero voltage.

[0103] Example 2:

[0104] This embodiment proposes a three-phase bidirectional high-frequency isolated AC / DC converter, which includes three single-phase bidirectional high-frequency isolated AC / DC converters. Each single-phase bidirectional high-frequency isolated AC / DC converter includes an H4 bridge, a first inductor, a first intermediate capacitor, a second intermediate capacitor, a transformer, a second inductor, and a fifth switch.

[0105] The H4 bridge includes four bridge arms, each of which includes a switch. The common terminal of the third switch and the first switch serves as the second connection terminal of the H4 bridge; the common terminal of the third switch and the fourth switch serves as the first connection terminal of the H4 bridge; the common terminal of the first switch and the second switch serves as the third connection terminal of the H4 bridge; and the common terminal of the fourth switch and the second switch serves as the fourth connection terminal of the H4 bridge.

[0106] Specifically, the first connection terminal of the H4 bridge is connected to the first port of the converter via the first inductor; the third connection terminal of the H4 bridge is connected to the second port of the converter; the second connection terminal of the H4 bridge is connected to the first end of the first side of the transformer via the first intermediate capacitor; and the fourth connection terminal of the H4 bridge is connected to the second end of the first side of the transformer.

[0107] The first terminal of the second side of the transformer is connected to the third port of the converter; the second terminal of the second side of the transformer is connected to the fourth port of the converter via the second intermediate capacitor and the second inductor; the common terminal of the second intermediate capacitor and the second inductor is connected to the first terminal of the second side of the transformer via the fifth switch.

[0108] The third ports of three single-phase bidirectional high-frequency isolated AC / DC converters are connected together as the third port of the three-phase bidirectional high-frequency isolated AC / DC converter, and the fourth ports of three single-phase bidirectional high-frequency isolated AC / DC converters are connected together as the fourth port of the three-phase bidirectional high-frequency isolated AC / DC converter.

[0109] The second ports of the three single-phase bidirectional high-frequency isolated AC-DC converters are connected together, and the first ports of the three single-phase bidirectional high-frequency isolated AC-DC converters are respectively used as the A, B, and C three-phase ports;

[0110] The third terminal of each of the fifteen switches is a control terminal, which is suitable for controlling the working state of the fifteen switches under the control of the control signal connected to the control terminal, so that the converter is in rectification mode or inverter mode. Each of the fifteen switches has three working states: conduction from the first terminal to the second terminal, conduction from the second terminal to the first terminal, and disconnection.

[0111] Similar to Example 1, the fifth switch S5 in each phase has two connection methods, such as... Figure 19 , Figure 20 As shown.

[0112] It should be noted that, in practical implementation, this three-phase bidirectional high-frequency isolated AC / DC converter can be used as a three-phase four-wire bidirectional high-frequency isolated AC / DC converter, such as... Figure 21 , 22 As shown, the second ports of three single-phase bidirectional high-frequency isolated AC / DC converters are connected together, and their common terminal is grounded, serving as the N line of a three-phase four-wire system; the A, B, and C phase ports are respectively connected to the first terminal of the three-phase power supply, and the second terminal of the three-phase power supply is connected together and then grounded; or the A, B, and C phase ports are respectively connected to the first terminal of three loads, and the second terminal of the three loads is connected together and then grounded.

[0113] In practical implementation, each single-phase AC-DC converter adopts a modular design, with each phase controlled independently. The three-phase bidirectional high-frequency isolated AC-DC converter topology is composed of three bidirectional high-frequency isolated AC-DC converter topologies, so its operating mode is similar to that of Example 1, and will not be described again here.

[0114] In summary, compared with existing technologies, it has the following beneficial effects:

[0115] 1. The embodiments of the present invention employ a single-stage energy conversion to realize a bidirectional isolated AC-DC converter, which uses fewer components and fewer sampling circuits, resulting in lower equipment cost and smaller size. Simultaneously, the single-stage energy conversion improves operating efficiency.

[0116] 2. The proposed three-phase bidirectional high-frequency isolated AC / DC converter adopts a modular design, consisting of three independent single-phase bidirectional high-frequency isolated AC / DC converters. In this topology, there is no coupling between the three phases, which significantly simplifies the system control complexity and facilitates efficient control.

[0117] 3. A bidirectional high-frequency isolated AC / DC converter topology eliminates the bus capacitor in the traditional structure, fundamentally avoiding the lifespan bottleneck caused by the aging of the bus capacitor, and significantly improving the long-term operational reliability and service life of the converter.

[0118] 4. Since the three-phase topology is directly composed of three decoupled single-phase circuits, when the input power supply voltage exhibits phase interleaving, the output terminals of the three-phase circuit will produce the same phase interleaving, which will greatly reduce the voltage ripple, and thus greatly reduce the filter capacitor.

[0119] 5. In the embodiments of the present invention, the transformer of the bidirectional high-frequency isolated AC-DC converter does not perform the function of energy storage. A double-ended transformer can be used. In the double-ended transformer, energy transfer is achieved through bidirectional current drive. It does not need to rely entirely on the magnetic core to store energy. Therefore, the air gap can be designed to be extremely small, thereby effectively reducing the transformer volume and reducing the influence of parasitic parameters such as leakage inductance.

[0120] 6. Some components are turned on at zero voltage, which reduces losses.

[0121] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0122] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single-phase bidirectional high-frequency isolated AC / DC converter, characterized in that, It includes the H4 bridge, the first inductor, the second inductor, the first intermediate capacitor, the second intermediate capacitor, the transformer, and the fifth switch; The H4 bridge includes four bridge arms, each of which includes a switch. The common terminal of the third switch and the first switch serves as the second connection terminal of the H4 bridge; the common terminal of the third switch and the fourth switch serves as the first connection terminal of the H4 bridge; the common terminal of the first switch and the second switch serves as the third connection terminal of the H4 bridge; and the common terminal of the fourth switch and the second switch serves as the fourth connection terminal of the H4 bridge. Specifically, the first connection terminal of the H4 bridge is connected to the first port of the converter via the first inductor; the third connection terminal of the H4 bridge is connected to the second port of the converter; the second connection terminal of the H4 bridge is connected to the first end of the first side of the transformer via the first intermediate capacitor; and the fourth connection terminal of the H4 bridge is connected to the second end of the first side of the transformer. The first terminal of the second side of the transformer is connected to the third port of the converter; the second terminal of the second side of the transformer is connected to the fourth port of the converter via the second intermediate capacitor and the second inductor; the common terminal of the second intermediate capacitor and the second inductor is connected to the first terminal of the second side of the transformer via the fifth switch. The third terminal of each of the five switches is a control terminal, which is suitable for controlling the working state of the five switches under the control of the control signal connected to the control terminal, so that the converter is in rectification mode or inverter mode. Each of the five switches has three working states: conduction from the first terminal to the second terminal, conduction from the second terminal to the first terminal, and disconnection.

2. The single-phase bidirectional high-frequency isolated AC / DC converter as described in claim 1, characterized in that, The transformer is a two-ended transformer.

3. The single-phase bidirectional high-frequency isolated AC / DC converter as described in claim 1, characterized in that, Each arm of the H4 bridge includes a switch with a reverse-parallel freewheeling diode.

4. The single-phase bidirectional high-frequency isolated AC / DC converter as described in any one of claims 1 to 3, characterized in that, The fifth switch includes a switching transistor with a reverse parallel freewheeling diode; The switching method of the reverse parallel freewheeling diode includes: the anode of the freewheeling diode is connected to the common terminal of the second intermediate capacitor and the second inductor; Alternatively, the cathode of the diode can be connected to the common terminal of the second intermediate capacitor and the second inductor.

5. A three-phase bidirectional high-frequency isolated AC / DC converter, characterized in that, It includes three single-phase bidirectional high-frequency isolated AC / DC converters. Each single-phase bidirectional high-frequency isolated AC / DC converter includes an H4 bridge, a first inductor, a first intermediate capacitor, a second intermediate capacitor, a transformer, a second inductor, and a fifth switch. The H4 bridge includes four bridge arms, each of which includes a switch. The common terminal of the third switch and the first switch serves as the second connection terminal of the H4 bridge; the common terminal of the third switch and the fourth switch serves as the first connection terminal of the H4 bridge; the common terminal of the first switch and the second switch serves as the third connection terminal of the H4 bridge; and the common terminal of the fourth switch and the second switch serves as the fourth connection terminal of the H4 bridge. Specifically, the first connection terminal of the H4 bridge is connected to the first port of the converter via the first inductor; the third connection terminal of the H4 bridge is connected to the second port of the converter; the second connection terminal of the H4 bridge is connected to the first end of the first side of the transformer via the first intermediate capacitor; and the fourth connection terminal of the H4 bridge is connected to the second end of the first side of the transformer. The first terminal of the second side of the transformer is connected to the third port of the converter; the second terminal of the second side of the transformer is connected to the fourth port of the converter via the second intermediate capacitor and the second inductor; the common terminal of the second intermediate capacitor and the second inductor is connected to the first terminal of the second side of the transformer via the fifth switch. The third ports of three single-phase bidirectional high-frequency isolated AC / DC converters are connected together as the third port of the three-phase bidirectional high-frequency isolated AC / DC converter, and the fourth ports of three single-phase bidirectional high-frequency isolated AC / DC converters are connected together as the fourth port of the three-phase bidirectional high-frequency isolated AC / DC converter. The second ports of the three single-phase bidirectional high-frequency isolated AC-DC converters are connected together, and the first ports of the three single-phase bidirectional high-frequency isolated AC-DC converters are respectively used as the A, B, and C three-phase ports; The third terminal of each of the fifteen switches is a control terminal, which is suitable for controlling the working state of the fifteen switches under the control of the control signal connected to the control terminal, so that the converter is in rectification mode or inverter mode. Each of the fifteen switches has three working states: conduction from the first terminal to the second terminal, conduction from the second terminal to the first terminal, and disconnection.

6. The three-phase bidirectional high-frequency isolated AC / DC converter as described in claim 5, characterized in that, The transformer is a two-ended transformer.

7. The three-phase bidirectional high-frequency isolated AC / DC converter as described in claim 5, characterized in that, Each arm of the H4 bridge includes a switch with a reverse-parallel freewheeling diode.

8. The three-phase bidirectional high-frequency isolated AC / DC converter as described in claim 5, characterized in that, The fifth switch includes a switching transistor with a reverse parallel freewheeling diode; The switching method of the reverse parallel freewheeling diode includes: the anode of the freewheeling diode is connected to the common terminal of the second intermediate capacitor and the second inductor; Alternatively, the cathode of the diode can be connected to the common terminal of the second intermediate capacitor and the second inductor.

9. The three-phase bidirectional high-frequency isolated AC / DC converter as described in any one of claims 5 to 8, characterized in that, The second ports of three single-phase bidirectional high-frequency isolated AC / DC converters are connected together, and their common terminal is grounded. In rectification mode, the A, B, and C phase ports are connected to the first terminals of the three-phase power supply, and the second terminals of the three-phase power supply are connected together and then grounded; in inverter mode, the A, B, and C phase ports are connected to the first terminals of the three loads, and the second terminals of the three loads are connected together and then grounded. The grounding terminal serves as the neutral (N) line in a three-phase four-wire system.

10. The three-phase bidirectional high-frequency isolated AC / DC converter as described in any one of claims 5 to 8, characterized in that, The three single-phase bidirectional high-frequency isolated AC / DC converters all adopt a modular design, with each phase controlled independently.

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