A bidirectional ac-dc conversion device and a charging pile

Abstract

The application provides a bidirectional AC-DC conversion device and a charging pile, relates to the technical field of energy, and is used for retaining high power density and low ripple advantage and realizing bidirectional energy transmission of the charging pile. The bidirectional AC-DC conversion device comprises a three-phase inductor circuit, a power conversion circuit, a bus capacitor and three capacitor branches. The power conversion circuit comprises a plurality of parallelly connected switch tube bridge arm circuits. The first end of the three-phase inductor circuit is used for receiving or outputting three-phase alternating current, the second end of the three-phase inductor circuit is connected with the bridge arm midpoints of the plurality of switch tube bridge arm circuits in correspondence respectively, the two ends of the bridge arm of the plurality of switch tube bridge arm circuits are connected with the two ends of the bus capacitor, the two ends of the bus capacitor are used for receiving or outputting direct current, the midpoint of the bus capacitor is connected with the first ends of the three capacitor branches, and the second ends of the three capacitor branches are connected with the first end of the three-phase inductor circuit. Each phase inductor circuit in the three-phase inductor circuit comprises an inductor and a coupled inductor which are connected in series.

Description

Technical Field

[0001] This application relates to the field of energy technology, and in particular to a bidirectional AC-DC converter and a charging pile. Background Technology

[0002] AC-DC converters based on three-phase interleaved parallel coupling inductors have been widely used as rectifiers in charging equipment such as charging piles due to their advantages of high power density and low current ripple.

[0003] However, with the rapid development of new energy technologies, the functional requirements for charging piles have evolved from unidirectional energy transmission to bidirectional energy transmission. For example, when an electric vehicle is connected to a charging pile, the charging pile should not only be able to convert the AC power transmitted from the grid into DC power to supply the electric vehicle, but also be able to convert the received DC power into AC power to supply the grid.

[0004] Therefore, while retaining the advantages of high power density and low ripple, how to achieve bidirectional energy transmission has become an urgent problem to be solved. Utility Model Content

[0005] This application provides a bidirectional AC-DC converter and a charging pile, which enables bidirectional energy transmission of the charging pile while retaining the advantages of high power density and low ripple.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, a bidirectional AC-DC converter is provided, comprising: a three-phase inductor circuit, a power conversion circuit, a bus capacitor, and three capacitor branches. The power conversion circuit includes multiple parallel-connected switching transistor bridge arm circuits. The first terminal of the three-phase inductor circuit is used to receive or output three-phase AC power. The second terminal of the three-phase inductor circuit is connected to the midpoint of each of the bridge arms of the multiple switching transistor bridge arm circuits. The two ends of each bridge arm of the multiple switching transistor bridge arm circuits are connected to the two ends of the bus capacitor. The two ends of the bus capacitor are used to receive or output DC power. The midpoint of the bus capacitor is connected to the first terminal of each of the three capacitor branches, and the second terminals of the three capacitor branches are connected to the first terminal of the three-phase inductor circuit. Each phase inductor circuit includes an inductor and a coupling inductor connected in series, with one end of the inductor connected to the common terminal of the coupling inductor.

[0008] In the above technical solution, multiple switching transistor bridge arm circuits are used to replace the rectifier circuit (i.e., a combination of diode bridge arms and bidirectional switches). The conversion between AC and DC power can be achieved by controlling the switching transistors in the bridge arm circuits to turn them on or off. When electrical energy is input from the AC terminal of the bidirectional AC-DC converter and output from the DC terminal, the bidirectional AC-DC converter can function as a rectifier to convert AC power (e.g., from the power grid) into DC power to supply power to a load (e.g., an electric vehicle). When electrical energy is input from the DC terminal of the bidirectional AC-DC converter and output from the AC terminal, the bidirectional AC-DC converter can function as an active inverter to convert DC power supplied by a load or DC power source into AC power to discharge to the power grid.

[0009] Furthermore, the three-phase inductor circuit includes an inductor and a coupling inductor, which can be equivalent to a boost inductor used to stabilize the input current waveform, synchronizing it with the phase of the input voltage, improving the power factor, and reducing harmonics. Using a coupling inductor also reduces the core size and winding volume, which can improve power density to some extent. The bus capacitor is connected to the first terminal of the three capacitor branches, and the second terminal of the three capacitor branches is connected to the three-phase inductor circuit. This not only stabilizes the midpoint voltage of the bus capacitor, but the three capacitor branches and the three-phase inductor circuit also form a three-phase filter, capable of filtering out low-frequency current ripple and high-frequency switching noise, thereby improving voltage stability.

[0010] Therefore, it can be seen that the bidirectional AC-DC conversion device provided in this application embodiment can meet the requirements of bidirectional energy transmission while retaining the advantages of high power density and low ripple.

[0011] In conjunction with the first aspect, in one implementation, the switching transistor bridge arm circuit includes a switching transistor bridge arm and a bidirectional switch, the first end of which is connected to the midpoint of the switching transistor bridge arm, and the second end of which is connected to the midpoint of the bus capacitor.

[0012] In conjunction with the first aspect, in one implementation, the switching transistor bridge arm includes a first switching transistor and a second switching transistor connected in series and having the same freewheeling direction, and the connection point of the first switching transistor and the second switching transistor is the midpoint of the bridge arm of the switching transistor bridge arm circuit.

[0013] Based on the above technical solution, a possible topology for the switching bridge arm is provided, and the connection between the switching bridge arm and the bidirectional switch constitutes a T-type three-level topology. When using this topology, the bidirectional AC-DC power conversion device can reduce the number and size of components and lower losses.

[0014] In conjunction with the first aspect, in one implementation, the bidirectional switch includes two switching transistors with opposite freewheeling directions.

[0015] Based on the above technical solution, bidirectional controllable current transmission can be achieved by actively controlling the conduction state of two switching transistors with opposite freewheeling directions.

[0016] In conjunction with the first aspect, in one implementation, the bidirectional switch includes two IGBTs connected by a common collector or a common emitter.

[0017] In conjunction with the first aspect, in one implementation, the bidirectional switch includes two MOS transistors connected in a common-drain or common-source configuration.

[0018] Based on the above technical solutions, several possible topologies of bidirectional switches are provided. When IGBTs are used in the switching bridge arm, the bidirectional switch can be connected by a common collector or a common emitter. When MOS is selected as the switching transistor in the switching bridge arm, the bidirectional switch can be connected by a common drain or a common source. That is, the bidirectional switch and the switching bridge arm can be the same type of switching transistor to improve the reliability of the bidirectional AC-DC conversion device.

[0019] In conjunction with the first aspect, in one implementation, the switching transistor bridge arm circuit includes: a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor connected in series with the same freewheeling direction, and a first diode and a second diode connected in series between a first coupling point and a second coupling point. The first coupling point is the connection point between the first and second switching transistors, and the second coupling point is the connection point between the third and fourth switching transistors. The anode of the first diode and the cathode of the second diode are both connected to the midpoint of the bus capacitor, and the connection point between the second and third switching transistors is the midpoint of the bridge arm of the switching transistor bridge arm circuit.

[0020] Based on the above technical solution, a possible topology for a switching transistor bridge arm is provided. This switching transistor bridge arm circuit has a neutral point clamped (NPC) topology. When using this topology, the bidirectional AC-DC power conversion device can clamp the turn-off voltage of the switching transistor to half of the DC bus voltage, reducing the voltage stress on the switching transistor.

[0021] In conjunction with the first aspect, in one implementation, the switching transistor bridge arm circuit includes: a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor connected in series with the same freewheeling direction; and a fifth switching transistor and a sixth switching transistor connected in series between a first coupling point and a second coupling point with the same freewheeling direction. The first coupling point is the connection point between the first and second switching transistors, and the second coupling point is the connection point between the third and fourth switching transistors. The connection point between the fifth and sixth switching transistors is also connected to the midpoint of the bus capacitor, and the connection point between the second and third switching transistors is the midpoint of the bridge arm of the switching transistor bridge arm circuit.

[0022] Based on the above technical solution, a possible topology for the switching transistor bridge arm is provided. This switching transistor bridge arm circuit uses an active neutral point clamped (ANPC) topology. When using this topology, the bidirectional AC-DC power converter can precisely adjust the current at the midpoint of the bridge arm, while avoiding the reverse recovery problem of the diodes, thus improving the reliability of the bidirectional AC-DC power converter.

[0023] In conjunction with the first aspect, in one implementation, the switching transistor bridge arm circuit includes: a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor connected in series and having the same freewheeling direction, and a first capacitor connected between a first coupling point and a second coupling point. The first coupling point is the connection point between the first and second switching transistors, and the second coupling point is the connection point between the third and fourth switching transistors. The connection point between the second and third switching transistors is the midpoint of the bridge arm of the switching transistor bridge arm circuit.

[0024] Based on the above technical solution, a possible topology for the switching transistor bridge arm is provided. This switching transistor bridge arm circuit uses a flying capacitor neutral point clamped (FC NPC) topology. When this topology is adopted, the bidirectional AC-DC power conversion device can enhance the voltage clamping capability, further reduce common-mode noise generated by the switching transistor's on / off state, and improve the stability of the output voltage.

[0025] In a second aspect, a charging pile is provided, the charging pile including a DC-DC converter, a charging gun, and a bidirectional AC-DC converter as described in the first aspect or any implementation thereof, wherein the AC terminal of the bidirectional AC-DC converter is used to connect to an AC power source, and the DC terminal of the bidirectional AC-DC converter is connected to the charging gun through the DC-DC converter.

[0026] Understandably, the beneficial effects of the charging piles provided above can be compared with the beneficial effects of the bidirectional AC-DC conversion device provided in the first aspect or any implementation of the first aspect above, and will not be repeated here. Attached Figure Description

[0027] Figure 1 A schematic diagram illustrating a scenario where a charging pile charges an electric vehicle, as provided in an embodiment of this application.

[0028] Figure 2 This is a schematic diagram of the structure of a charging pile provided in an embodiment of this application;

[0029] Figure 3 A circuit topology diagram of an AC-DC power conversion device provided in this application embodiment;

[0030] Figure 4 This is a schematic diagram of the structure of a bidirectional AC-DC power conversion device provided in an embodiment of this application;

[0031] Figure 5 A circuit topology diagram of a bidirectional AC-DC power conversion device provided in this application embodiment;

[0032] Figure 6 Circuit topology diagrams of some bidirectional switches provided in embodiments of this application;

[0033] Figure 7 A circuit topology diagram of another bidirectional AC-DC power conversion device provided in the embodiments of this application;

[0034] Figure 8 A circuit topology diagram of another bidirectional AC-DC power conversion device provided in the embodiments of this application;

[0035] Figure 9 A circuit topology diagram of another bidirectional AC-DC power conversion device provided in the embodiments of this application;

[0036] Figure 10 A circuit topology diagram of a bidirectional AC-DC power conversion device is provided for embodiments of this application. Detailed Implementation

[0037] The following sections will discuss the fabrication and use of the various embodiments in detail. However, it should be understood that many of the applicable utility model concepts provided in this application can be implemented in a variety of specific environments. The specific embodiments discussed are merely illustrative of specific ways to implement and use this application and technology, and do not limit the scope of this application.

[0038] Unless otherwise defined, all technical terms used herein have the same meaning as commonly known to one of ordinary skill in the art.

[0039] In this application, "multiple" refers to two or more. The embodiments of this application use terms such as "first" and "second" to distinguish objects with similar names, functions, or roles. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order.

[0040] It should be noted that, in this application, the terms "exemplary" or "for example" are used to indicate that something is being described as an example, illustration, or illustration. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0041] Before introducing the embodiments of this application, the application scenarios involved in this application will be introduced first.

[0042] Figure 1 An example is given of a scenario where a charging station charges an electric vehicle. For example... Figure 1 As shown in (a) and (b), the charging pile 200 is used to receive the AC power output from the power grid 100, convert the AC power into stable DC power and then deliver it to the electric vehicle 300 to charge the electric vehicle 300.

[0043] In some embodiments, such as Figure 1 As shown in (a) of the diagram, the charging pile 200 is a split-type charging pile. Exemplarily, the charging pile 200 includes a charging host 210, one or more charging terminals 220, and one or more charging guns 230. The charging host 210 is connected to each charging terminal 220, and each charging terminal 220 is connected to at least one charging gun 230. Each charging gun 230 is used to connect to an electric vehicle 300. In one embodiment, one charging terminal 220 can connect to at least two charging guns 230, and at least two charging guns 230 can connect to one electric vehicle 300; this embodiment does not specifically limit the scope of the invention.

[0044] The aforementioned charging terminal 220 may include a cabinet (also known as a shell), a human-machine interface, a charging control unit, and a metering and billing unit, and is used for information exchange, energy transmission, and metering and billing with the electric vehicle 300.

[0045] The aforementioned electric vehicle 300 is a vehicle powered by electricity. The types of electric vehicles 300 include pure electric vehicles (pure EV / battery EV), hybrid electric vehicles (HEV), range-extended electric vehicles (REEV), or plug-in hybrid electric vehicles (PHEV), etc. This application embodiment does not limit the specific type of electric vehicle.

[0046] In other embodiments, such as Figure 1 As shown in (b) above, the charging pile 200 is an integrated charging pile. For example, the human-machine interface, charging control unit, and metering unit of the charging pile 200 are directly installed in the charging host 210, in conjunction with the aforementioned... Figure 1 Compared to the scenario shown in (a), the charging pile 200 may include a charging host 210 and one or more charging guns 230 connected to the charging host 210, but does not include the charging terminal 220.

[0047] The above Figure 1 The charging host 210 shown in (a) and (b) includes multiple power conversion devices for converting the alternating current output from the power grid 100 into stable direct current before supplying it to the charging terminal 220. These multiple power conversion devices may include multiple AC-DC converters and multiple direct current-to-direct current (DC-DC) converters.

[0048] The following combination Figure 2 ,right Figure 1 The structure of the charging pile shown is described in detail.

[0049] In one embodiment, Figure 2 Example Figure 1 The structure of the split-type charging pile is shown in (a) above. Figure 2As shown, in the charging pile 200, the charging host 210 includes multiple AC-DC converters 211, multiple DC-DC converters 212, a DC bus 213, and a power distribution device 214. The AC terminal of the AC-DC converter 211 is connected to the power grid 100. The DC terminal of the AC-DC converter 211 is connected to the first DC terminal of the DC-DC converter 212 via the DC bus 213. The second DC terminal of the DC-DC converter 212 is connected to the charging terminal 220 in the charging pile 200 via the power distribution device 214. The charging terminal 220 is connected to the charging gun 230, which is used to connect to the electric vehicle 300 to charge the electric vehicle 300.

[0050] In specific implementation, the AC-DC converter 211 converts the alternating current output from the power grid 100 into direct current and outputs it to the DC bus 213. The DC-DC converter 212 further converts the DC power obtained from the DC bus 213 into DC power suitable for the electric vehicle 300 and outputs it to the power distribution device 214. The power distribution device 214 dynamically distributes the DC power output from the DC-DC converter 212 according to the actual charging power required by the electric vehicle 300, and transmits the distributed power to the charging gun 230 through the charging terminal 220, so that the power output by the charging gun 230 to the electric vehicle 300 meets the charging needs of the electric vehicle 300.

[0051] The above Figure 2 The example illustrates the case where multiple AC-DC converters 211 and multiple DC-DC converters 212 are integrated separately, meaning that the AC-DC converters 211 and DC-DC converters 212 in the charging pile 200 can be set up independently and integrated into different housings.

[0052] In another embodiment, the charging pile 200 may include multiple AC-DC conversion modules. Each AC-DC conversion module includes interconnected AC-DC conversion devices 211 and DC-DC conversion devices 212. Specifically, AC-DC conversion devices 211 and 212 can be integrated into a single housing as the AC-DC conversion module. This AC-DC conversion module converts the alternating current output from the power grid 100 into direct current, and further converts the direct current into direct current suitable for the electric vehicle 300 before outputting it to the power distribution device 214. The power distribution device 214 dynamically distributes the received direct current according to the actual charging power required by the electric vehicle 300, and delivers the distributed power to the charging gun 230, so that the power output from the charging gun 230 to the electric vehicle 300 meets the charging requirements of the electric vehicle 300.

[0053] The following are Figure 3Taking the circuit topology shown as an example, the circuit topology structure of the above-mentioned AC-DC converter will be explained in detail.

[0054] like Figure 3 As shown, the AC-DC conversion device 400 includes a three-phase inductor circuit 410, an AC-DC conversion circuit 420, and a bus capacitor 430 connected in sequence.

[0055] Reference Figure 3 Each phase of the three-phase inductor circuit 410 includes an inductor and a coupling inductor connected in sequence. Taking the first phase inductor circuit as an example, it includes inductor La1 and coupling inductor La2, with the common terminal of inductor La1 and coupling inductor La2 connected. Similarly, the common terminal of inductor Lb1 and coupling inductor Lb2 is connected, and the common terminal of inductor Lc1 and coupling inductor Lc2 is connected. Figure 3 Taking the topology of the coupled inductor La2 as an example, the upper inductor winding of the coupled inductor La2 is called the first winding, and the lower inductor winding is called the second winding. The opposite-named terminal of the first winding is connected to the same-named terminal of the second winding as the common terminal of the coupled inductor La2. The same-named terminal of the first winding is one output / input terminal of the coupled inductor La2, and the opposite-named terminal of the second winding is the other input / output terminal of the coupled inductor La2. Figure 3 The asterisk (*) indicates the corresponding terminal of the winding. This coupled inductor can also be called an autotransformer. Compared with traditional inductors, using an autotransformer can reduce the core size and the winding volume of the inductor, thereby improving the power density to a certain extent.

[0056] The first terminals of the three inductors (La1, Lb1, and Lc1) in the three-phase inductor circuit 410 serve as the three-phase AC input terminals (e.g., Va, Vb, and Vc) of the AC-DC power conversion device 400. The input and output terminals of the three coupled inductors (La2, Lb2, and Lc3) in the three-phase inductor circuit 410 are respectively connected to the six rectifier circuits in the AC-DC conversion circuit 420, and are connected to the midpoint of the bus capacitor 430 through the six rectifier circuits.

[0057] For example, the AC-DC conversion circuit 420 includes six bridge arms and six bidirectional switches, with each bridge arm and its corresponding bidirectional switch forming a rectifier circuit 421. For instance, two diodes Da1 and Da2 connected in series with the same freewheeling direction form the first bridge arm, the connection point of which is the midpoint of the first bridge arm, and the cathode of diode Da1 and the anode of diode Da2 form the two ends of the first bridge arm. Similarly, diodes Da3 and Da4 and bidirectional switch Sa2 form the second rectifier circuit; diodes Db1 and Db2 and bidirectional switch Sb1 form the third rectifier circuit; diodes Db3 and Db4 and bidirectional switch Sb2 form the fourth rectifier circuit; diodes Dc1 and Dc2 and bidirectional switch Sc1 form the fifth rectifier circuit; and diodes Dc3 and Dc4 and bidirectional switch Sc2 form the sixth rectifier circuit.

[0058] The midpoint of the bridge arm formed by diodes Da1 and Da2 is also connected to the midpoint of the bus capacitor 430 via a bidirectional switch Sa1. The bus capacitor 430 includes capacitors C1 and C2, and the connection point of capacitors C1 and C2 is the midpoint of the bus capacitor 430. The two ends of the bridge arm formed by diodes Da1 and Da2 are connected to the two ends of the bus capacitor 430, and respectively serve as the positive DC output terminal Vout+ and negative DC output terminal Vout- of the AC-DC power conversion device 400.

[0059] Continue to refer to Figure 3 The AC-DC converter 400 also includes three capacitors (Ca, Cb, and Cc). The first terminals of the three capacitors (Ca, Cb, and Cc) are connected to the first terminals of the three inductors (La1, Lb1, and Lc1), respectively. The second terminals of the three capacitors (Ca, Cb, and Cc) are coupled and connected as neutral points to the midpoint of the bus capacitor 430. This can be used to stabilize the midpoint voltage of the bus capacitor 430 and reduce current ripple.

[0060] With the rapid development of new energy technologies, the functional requirements for charging piles have evolved from unidirectional energy transmission to bidirectional energy transmission. For example, in Figure 1 and Figure 2 In the charging scenario shown, when the electric vehicle 300 is connected to the charging gun 230, the charging host 210 should not only convert the AC power transmitted from the power grid 100 into DC power to supply power to the electric vehicle 300, but also convert the DC power provided by the electric vehicle 300 into AC power and transmit the AC power back to the power grid 100. However, the aforementioned AC-DC converter 400 can only convert AC power to DC power, and cannot achieve DC-to-AC energy transfer.

[0061] Therefore, in order to meet the bidirectional energy transmission requirements of charging piles, this application provides a bidirectional AC-DC converter and a charging pile including the bidirectional AC-DC converter, which enables bidirectional energy transmission while retaining the advantages of high power density and low ripple. The bidirectional AC-DC converter provided in this application can be installed separately from the DC-DC converter (e.g., ...). Figure 2 (As shown), it can also be used with Figure 2 The DC-DC converters shown are integrated into a single AC-DC converter module, and this application does not specifically limit the scope of the embodiments therein. It is understood that the bidirectional AC-DC converters provided in this application can be applied not only to applications such as... Figure 1 and Figure 2 The charging pile 200 shown can also be applied to charging equipment such as power modules in charging stations and on-board chargers for electric vehicles. As an example and not a limitation, this application describes the application of the bidirectional AC-DC converter to the charging pile 200.

[0062] The specific structure of the bidirectional AC-DC converter provided in the embodiments of this application will be described below with reference to the accompanying drawings.

[0063] Figure 4 This is a schematic diagram of a bidirectional AC-DC power conversion device provided in an embodiment of this application.

[0064] In some embodiments, such as Figure 4 As shown, the bidirectional AC-DC converter 500 provided in this application embodiment includes: a three-phase inductor circuit 510, a power conversion circuit 520, a bus capacitor 530, and three capacitor branches.

[0065] The following are Figure 4 Taking the illustrated topology as an example, the specific circuit topology of the bidirectional AC-DC power conversion device 500 provided in this application embodiment will be described and explained. In the bidirectional AC-DC power conversion device 500 provided in this application embodiment, the circuit topology of the three-phase inductor circuit 510, the bus capacitor 530, and the three capacitor branches can adopt the topology structure in related technologies. For example, they can be respectively connected to... Figure 3 The three-phase inductor circuit 410, bus capacitor 430, and three capacitors shown have the same topology.

[0066] Reference Figure 4The first terminal of the three-phase inductor circuit 510 is the three-phase AC input terminal (e.g., Va, Vb, and Vc) of the bidirectional AC-DC converter 500, used to receive or output three-phase AC power. The second terminal of the three-phase inductor circuit 510 is connected to the power conversion circuit 520. The power conversion circuit 520 includes multiple parallel switching transistor bridge arm circuits 521, and the second terminal of the three-phase inductor circuit 510 is connected to the midpoint of the bridge arm of each of the multiple switching transistor bridge arm circuits 521.

[0067] Reference Figure 4 Each phase inductor circuit in the three-phase inductor 510 includes an inductor and a coupling inductor connected in series. One end of the inductor is connected to the common terminal of the coupling inductor. For example, the common terminal of inductor La1 is connected to the common terminal of coupling inductor La2, the common terminal of inductor Lb1 is connected to the common terminal of coupling inductor Lb2, and the common terminal of inductor Lc1 is connected to the common terminal of coupling inductor Lc2. The common terminal of the coupling inductor is the connection point of the two windings, and the other two terminals of the autotransformer are the input and output terminals of the autotransformer, respectively. For example, the upper inductor winding of coupling inductor La2 is called the first winding, and the lower inductor winding is called the second winding. The opposite-named terminal of the first winding is connected to the same-named terminal of the second winding, serving as the common terminal of the coupled inductor La2. If the same-named terminal of the first winding is the output terminal of the coupled inductor La2, then the opposite-named terminal of the second winding is the input terminal of the coupled inductor La2. Alternatively, if the same-named terminal of the first winding is the input terminal of the coupled inductor La2, then the opposite-named terminal of the second winding is the output terminal of the coupled inductor La2. The coupled inductor formed using this connection method can also be called an autotransformer.

[0068] The two ends of the bridge arm circuit 521 of multiple switching transistors are connected to the two ends of the bus capacitor 530. The two ends of the bus capacitor 530 serve as the positive DC input / output terminal Vbus+ and the negative DC input / output terminal Vbus- of the bidirectional AC-DC converter, used to receive or output DC power.

[0069] like Figure 4 As shown, the midpoint of the bus capacitor 430 is also connected to the first end of the three capacitor branches, and the second end of the three capacitor branches is connected to the first end of the three-phase inductor circuit 510. The bus capacitor 430 includes capacitors C1 and C2, and the connection point of capacitors C1 and C2 is the midpoint of the bus capacitor 430. For example, the three capacitor branches include three capacitors (Ca, Cb, and Cc). The first ends of the three capacitors (Ca, Cb, and Cc) are coupled and connected as a neutral point to the midpoint of the bus capacitor 530. The second ends of the three capacitors (Ca, Cb, and Cc) are respectively connected to the first ends of three inductors (La1, Lb1, and Lc1). This connection of the three capacitors constitutes a star (Y) connection, which can stabilize the midpoint voltage of the bus capacitor 530 and reduce current ripple.

[0070] In the bidirectional AC-DC converter 500 provided in this application embodiment, multiple switching bridge arm circuits 521 are used instead of Figure 3 The rectifier circuit shown (i.e., the combination of diode bridge arms and bidirectional switches) can convert AC to DC or DC to AC by controlling the switching transistors in the switching bridge arm circuit 521 to be on or off. When electrical energy is input from the AC terminal of the bidirectional AC-DC converter 500 and output from the DC terminal, the bidirectional AC-DC converter 500 can function as a rectifier to convert AC power (e.g., from the power grid) into DC power to supply power to a load (e.g., an electric vehicle). When electrical energy is input from the DC terminal of the bidirectional AC-DC converter 500 and output from the AC terminal, the bidirectional AC-DC converter 500 can function as an active inverter to convert DC power supplied by a load or DC power source into AC power to discharge to the power grid.

[0071] Furthermore, the three-phase inductor circuit 510 includes an inductor and a coupling inductor, which can be equivalent to a boost inductor used to stabilize the input current waveform, synchronizing it with the phase of the input voltage, improving the power factor, and reducing harmonics. Using a coupling inductor also reduces the core size and winding volume, which can improve power density to some extent. The bus capacitor 530 is connected to the first terminal of the three capacitor branches, and the second terminal of the three capacitor branches is connected to the three-phase inductor circuit 510. This not only stabilizes the midpoint voltage of the bus capacitor 530, but the three capacitor branches and the three-phase inductor circuit 510 also form a three-phase filter, capable of filtering out low-frequency current ripple and high-frequency switching noise, thereby improving voltage stability.

[0072] Therefore, it can be seen that the bidirectional AC-DC converter 500 provided in this application embodiment can meet the requirements of bidirectional energy transmission while retaining the advantages of high power density and low ripple.

[0073] The following combination Figures 5 to 10 The following is a detailed introduction to several topologies of the aforementioned switch bridge arm circuit 521.

[0074] In one embodiment, such as Figure 5 As shown, the switching transistor bridge arm circuit 521 includes a switching transistor bridge arm and a bidirectional switch. The first terminal of the bidirectional switch is connected to the midpoint of the bridge arm, and the second terminal of the bidirectional switch is connected to the midpoint of the bus capacitor 530. The switching transistor bridge arm includes a first switching transistor Ta1 and a second switching transistor Ta2 connected in series with the same freewheeling direction. The connection point of the first switching transistor Ta1 and the second switching transistor Ta2 is the midpoint of the bridge arm of the switching transistor bridge arm circuit 521.

[0075] like Figure 5 As shown, taking the first switching transistor bridge arm circuit 521 as an example, the first switching transistor Ta1 and the second switching transistor Ta2 constitute a switching transistor bridge arm, and the connection point of the first switching transistor Ta1 and the second switching transistor Ta2 is the midpoint of the bridge arm of the first switching transistor bridge arm circuit 521. This midpoint of the bridge arm is connected to the midpoint of the bus capacitor 530 through the bidirectional switch Sa1, and the two ends of the switching transistor bridge arm are connected to the two ends of the bus capacitor 530. Similarly, switching transistors Ta5 and Ta6 and bidirectional switch Sa2 constitute the second switching transistor bridge arm circuit 521, switching transistors Tb1 and Tb2 and bidirectional switch Sb1 constitute the third switching transistor bridge arm circuit 521, switching transistors Tb5 and Tb6 and bidirectional switch Sb2 constitute the fourth switching transistor bridge arm circuit 521, switching transistors Tc1 and Tc2 and bidirectional switch Sc1 constitute the fifth switching transistor bridge arm circuit 521, and switching transistors Tc5 and Tc6 and bidirectional switch Sc2 constitute the sixth switching transistor bridge arm circuit 521.

[0076] Figure 6 The circuit topology diagrams of some bidirectional switches provided in the embodiments of this application are illustrated.

[0077] In one embodiment, such as Figure 6 As shown, the bidirectional switch includes two switching transistors with opposite freewheeling directions, used to achieve bidirectional controllable current transmission.

[0078] The following uses bidirectional switch Sa1 as an example to illustrate the topology of bidirectional switches Sa1 to Sc2. It is understood that, to simplify the control logic, bidirectional switches Sa1 to Sc2 can use the same topology.

[0079] like Figure 6 As shown, the bidirectional switch Sa1 can be configured in the following four circuit topologies.

[0080] In the first example, such as Figure 6 As shown in (a), the bidirectional switch comprises two insulated-gate bipolar transistors (IGBTs) connected by a common collector. In the second example, as... Figure 6 As shown in (b), the bidirectional switch includes two IGBTs connected in a common-emitter configuration. The bidirectional switch also includes two diodes connected in parallel with the two IGBTs, with the collectors of the IGBTs connected to the negative terminals of the diodes and the emitters of the IGBTs connected to the positive terminals of the diodes.

[0081] In the third instance, such as Figure 6As shown in (c), the bidirectional switch includes two metal-oxide-semiconductor field-effect transistors (MOSFETs) connected by a common drain. These MOSFETs can also be simply referred to as MOS transistors. In the fourth example, as... Figure 6 As shown in (d), the bidirectional switch includes two MOS transistors connected in common-source configuration. Each MOS transistor includes a reverse-biased body diode.

[0082] By way of example and not limitation, the embodiments of this application are illustrated by taking each switching transistor as an example, which includes an IGBT and a diode D.

[0083] Figure 7 A circuit topology diagram of another bidirectional AC-DC power conversion device provided in an embodiment of this application. Figure 6 Taking the topology of bidirectional switch Sa1 shown in (a) as an example, combined with Figure 5 The bidirectional switch Sa1 can be equivalently replaced by switches Ta3 and Ta4. For example, the switch bridge arm containing the first switch Ta1 and the second switch Ta2 can be called a vertical bridge, and the switch Ta3 and switch Ta4 can be called a horizontal bridge. This vertical bridge and the horizontal bridge form a "T" shape, and thus, the topology of the switch bridge arm circuit 521 can also be called a T-type three-level topology.

[0084] Figure 8 The circuit topology diagram of another bidirectional AC-DC power conversion device provided in the embodiments of this application is shown.

[0085] In one embodiment, such as Figure 8 As shown, the switching transistor bridge arm circuit 521 includes: a first switching transistor Ta1, a second switching transistor Ta2, a third switching transistor Ta3, and a fourth switching transistor Ta4 connected in series with the same freewheeling direction, and a first diode D1 and a second diode D2 connected in series between a first coupling point N1 and a second coupling point N2. The first coupling point N1 is the connection point between the first switching transistor Ta1 and the second switching transistor Ta2, and the second coupling point N2 is the connection point between the third switching transistor Ta3 and the fourth switching transistor Ta4. The anode of the first diode D1 and the cathode of the second diode D2 are both connected to the midpoint of the bus capacitor 530, and the connection point between the second switching transistor Ta2 and the third switching transistor Ta3 is the midpoint of the bridge arm of the switching transistor bridge arm circuit 521.

[0086] like Figure 8As shown, taking the first switching transistor bridge arm circuit 521 as an example, the second switching transistor Ta2 and the third switching transistor Ta3 are connected in series, and the first diode D1 and the second diode D2 are connected in series. These two series branches are connected in parallel between the first coupling point N1 and the second coupling point N2. The switching transistor bridge arm circuit 521 has an overall "I" shape, and its topology can be called the NPC topology. The NPC topology, through clamping diodes (i.e., the first diode D1 and the second diode D2), can clamp the turn-off voltage of the switching transistors to half of the DC bus voltage, reducing the voltage stress and losses of the switching transistors. Thus, by using switching transistors with lower withstand voltages, the hardware cost of the switching transistor devices can be reduced to some extent.

[0087] Figure 9 The circuit topology diagram is provided for another bidirectional AC-DC power conversion device according to an embodiment of this application.

[0088] In one embodiment, such as Figure 9 As shown, the switching transistor bridge arm circuit 521 includes: a first switching transistor Ta1, a second switching transistor Ta2, a third switching transistor Ta3, and a fourth switching transistor Ta4 connected in series with the same freewheeling direction; and a fifth switching transistor Ta5 and a sixth switching transistor Ta6 connected in series between a first coupling point N1 and a second coupling point N2 with the same freewheeling direction. The first coupling point N1 is the connection point between the first switching transistor Ta1 and the second switching transistor Ta2, and the second coupling point N2 is the connection point between the third switching transistor Ta3 and the fourth switching transistor Ta4. The connection point between the fifth switching transistor Ta5 and the sixth switching transistor Ta6 is also connected to the midpoint of the bus capacitor 530, and the connection point between the second switching transistor Ta2 and the third switching transistor Ta3 is the midpoint of the bridge arm of the switching transistor bridge arm circuit 521.

[0089] like Figure 9 As shown, taking the first switching transistor bridge arm circuit 521 as an example, the second switching transistor Ta2 and the third switching transistor Ta3 are connected in series, and the fifth switching transistor Ta5 and the sixth switching transistor Ta6 are connected in series. These two series branches are connected in parallel between the first coupling point N1 and the second coupling point N2. The switching transistor bridge arm circuit 521 presents an "I" shape, and its topology can be called the ANPC topology. The ANPC topology is achieved by... Figure 8 Replacing the clamping diodes (i.e., the first diode D1 and the second diode D2) with the fifth switch Ta5 and the sixth switch Ta6 not only allows for precise adjustment of the current at the midpoint of the bridge arm but also avoids the reverse recovery problem of the diodes. Thus, by employing... Figure 9 The topology shown can improve the reliability of bidirectional AC-DC power conversion devices to a certain extent.

[0090] Figure 10A circuit topology diagram of a bidirectional AC-DC power conversion device is provided for embodiments of this application.

[0091] In one embodiment, such as Figure 10 As shown, the switching transistor bridge arm circuit 521 includes: a first switching transistor Ta1, a second switching transistor Ta2, a third switching transistor Ta3, and a fourth switching transistor Ta4 connected in series with the same freewheeling direction, and a first capacitor Ca1 connected between a first coupling point N1 and a second coupling point N2. The first coupling point N1 is the connection point between the first switching transistor Ta1 and the second switching transistor Ta2, and the second coupling point N2 is the connection point between the third switching transistor Ta3 and the fourth switching transistor Ta4. The connection point between the second switching transistor Ta2 and the third switching transistor Ta3 is the midpoint of the bridge arm of the switching transistor bridge arm circuit 521.

[0092] like Figure 10 As shown, taking the first switching transistor bridge arm circuit 521 as an example, the second switching transistor Ta2 and the third switching transistor Ta3 are connected in series and then connected in parallel with the first capacitor Ca1 between the first coupling point N1 and the second coupling point N2. The switching transistor bridge arm circuit 521 has an overall "I" shape, and its topology can be called an FC NPC topology. Using the FC NPC topology enhances voltage clamping capability and further reduces common-mode noise generated by the switching transistors' on / off states, thereby improving the stability of the output voltage.

[0093] For ease of description, the process by which the bidirectional AC-DC converter 500 receives AC power and outputs DC power can be called a charging (or power supply) process or a forward transmission process, while the process by which the bidirectional AC-DC converter 500 receives DC power and outputs AC power can be called a discharging process or a reverse transmission process.

[0094] The above-described topologies of the switching transistor bridge arm circuit 521, illustrated in conjunction with the accompanying drawings, allow for different control methods based on these topologies. Each switching transistor bridge arm circuit 521 can operate in rectification mode to convert AC to DC and output it. Conversely, during reverse transmission, different control methods can be used to convert DC to AC and output it. The control methods for these different topologies can be found in related technologies and will not be elaborated upon here.

[0095] This application embodiment also provides a charging host, which includes a DC-DC converter, a power distribution device, and the bidirectional AC-DC converter described in the above embodiments. The AC terminal of the bidirectional AC-DC converter is used to connect to an AC power source (e.g., AC power supply). Figure 2The DC terminal of the bidirectional AC-DC converter (shown as power grid 100) is connected to the power distribution device via the DC-DC converter. The structure of the charging host can be referenced above. Figure 1 or Figure 2 The structure and circuit topology of the charging host 210 and the bidirectional AC-DC converter shown can be referred to the above. Figure 4 and Figure 5 , Figures 7 to 10 The circuit topology of the bidirectional AC-DC converter 500 shown in any of the attached figures.

[0096] This application embodiment also provides a charging pile, which includes a DC-DC converter, a charging gun, and the bidirectional AC-DC converter described in the above embodiments. The AC terminal of the bidirectional AC-DC converter is used to connect to an AC power source (e.g., AC power supply). Figure 2 The DC terminal of the bidirectional AC-DC converter (shown as power grid 100) is connected to the charging gun via the DC-DC converter. The structure of the charging pile can be referenced above. Figure 1 or Figure 2 The structure and circuit topology of the bidirectional AC-DC converter in the charging pile 200 shown can be referred to the above. Figure 4 and Figure 5 , Figures 7 to 10 The circuit topology of the bidirectional AC-DC converter 500 shown in any of the attached figures.

[0097] The detailed description of the charging host and charging pile mentioned above can be found in [reference]. Figure 1 and Figure 2 The relevant statements and analyses of the beneficial effects of the charging host and the charging pile can be applied to the bidirectional AC-DC converter 500, and will not be repeated here in the embodiments of this application.

[0098] Finally, it should be noted that the above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A bidirectional AC-DC converter, characterized in that, The bidirectional AC-DC converter includes: a three-phase inductor circuit, a power conversion circuit, a bus capacitor, and three capacitor branches; the power conversion circuit includes multiple parallel-connected switch bridge arm circuits. The first terminal of the three-phase inductor circuit is used to receive or output three-phase AC power. The second terminal of the three-phase inductor circuit is connected to the midpoint of the bridge arm of the plurality of switching transistor bridge arm circuits respectively. The two ends of the bridge arm of the plurality of switching transistor bridge arm circuits are connected to the two ends of the bus capacitor. The two ends of the bus capacitor are used to receive or output DC power. The midpoint of the bus capacitor is connected to the first terminal of the three capacitor branches. The second terminals of the three capacitor branches are connected to the first terminal of the three-phase inductor circuit. Each phase inductor circuit in the three-phase inductor circuit includes an inductor and a coupling inductor connected in series. One end of the inductor is connected to the common terminal of the coupling inductor.

2. The bidirectional AC-DC converter according to claim 1, characterized in that, The switching transistor bridge arm circuit includes a switching transistor bridge arm and a bidirectional switch. The first end of the bidirectional switch is connected to the midpoint of the switching transistor bridge arm, and the second end of the bidirectional switch is connected to the midpoint of the bus capacitor.

3. The bidirectional AC-DC converter according to claim 2, characterized in that, The switching transistor bridge arm includes a first switching transistor and a second switching transistor connected in series with the same freewheeling direction. The connection point of the first switching transistor and the second switching transistor is the midpoint of the bridge arm of the switching transistor bridge arm circuit.

4. The bidirectional AC-DC converter according to claim 2 or 3, characterized in that, The bidirectional switch includes two switching transistors with opposite freewheeling directions.

5. The bidirectional AC-DC converter according to claim 4, characterized in that, The bidirectional switch comprises two IGBTs connected by a common collector or a common emitter.

6. The bidirectional AC-DC converter according to claim 4, characterized in that, The bidirectional switch includes two MOS transistors connected in a common-drain or common-source configuration.

7. The bidirectional AC-DC converter according to claim 1, characterized in that, The switching transistor bridge arm circuit includes: a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor connected in series with the same freewheeling direction; and a first diode and a second diode connected in series between a first coupling point and a second coupling point. The first coupling point is the connection point between the first switching transistor and the second switching transistor, and the second coupling point is the connection point between the third switching transistor and the fourth switching transistor. The anode of the first diode and the cathode of the second diode are both connected to the midpoint of the bus capacitor, and the connection point of the second switch and the third switch is the midpoint of the bridge arm of the switch bridge arm circuit.

8. The bidirectional AC-DC converter according to claim 1, characterized in that, The switching transistor bridge arm circuit includes: a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor connected in series with the same freewheeling direction; and a fifth switching transistor and a sixth switching transistor connected in series between a first coupling point and a second coupling point with the same freewheeling direction. The first coupling point is the connection point between the first switching transistor and the second switching transistor, and the second coupling point is the connection point between the third switching transistor and the fourth switching transistor. The connection point of the fifth and sixth switching transistors is also connected to the midpoint of the bus capacitor, and the connection point of the second and third switching transistors is the midpoint of the bridge arm of the switching transistor bridge arm circuit.

9. The bidirectional AC-DC converter according to claim 1, characterized in that, The switching transistor bridge arm circuit includes: a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor connected in series with the same freewheeling direction, and a first capacitor connected between a first coupling point and a second coupling point. The first coupling point is the connection point between the first switching transistor and the second switching transistor, and the second coupling point is the connection point between the third switching transistor and the fourth switching transistor. The connection point between the second and third switching transistors is the midpoint of the bridge arm of the switching transistor bridge arm circuit.

10. A charging pile, characterized in that, The charging pile includes a DC-DC converter, a charging gun, and a bidirectional AC-DC converter as described in any one of claims 1 to 9. The AC terminal of the bidirectional AC-DC converter is used to connect to an AC power source, and the DC terminal of the bidirectional AC-DC converter is connected to the charging gun through the DC-DC converter.

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