Single-phase and three-phase compatible conversion circuit and vehicle charger

Abstract

The present invention discloses a single-phase and three-phase compatible conversion circuit, which includes: an EMC module, a PFC module, a switch K1 and a control module, the EMC module being connected between wires A, B, C and N of the power grid and the PFC module, three wires (A1, B1, C1) coming out of the EMC module being connected to the PFC module, and the three wires (A1, B1, C1) being connected respectively to a virtual center provided via capacitors (CX1, CX2, CX3), the virtual center being connected to the center of the bus of the PFC module via the switch (K1), and the control module being configured to detect an input signal from the power grid and control the state of the switch (K1) according to the type of input signal from the power grid.The technical solution of the present invention makes it possible to reduce common-mode noise in three-phase conversion mode and to ensure control in three-phase conversion mode by which the bus voltage can be regulated over a wide range; and to reduce the influence of common-mode noise on the DC side on the CME input in single-phase conversion mode. Figure 1.

Description

Title of the invention: Single-phase and three-phase compatible conversion circuit and vehicle charger Technical field

[0001] The present invention relates to the technical field of recharging electric vehicles, in particular relates to a single-phase and three-phase compatible conversion circuit and a vehicle charger. Prior art

[0002] To meet the requirements on energy saving and emission reduction and to promote green transportation, the demand on new energy vehicles is becoming more and more increasing, among which electric vehicles are becoming the main force. A vehicle charger is an important part of an electric vehicle, which helps the electric vehicle to form a non-fixed energy zone and energy form. The single-phase and three-phase compatible vehicle charger is widely used in various power grid environments, in particular, the three-phase vehicle charger can reduce the waiting time for charging.

[0003] Although the single-phase and three-phase compatible vehicle charger can bring various conveniences to the charging of electric vehicles, its main circuit design has many disadvantages. For the single-phase and three-phase compatible vehicle charger, switching between the single-phase and three-phase operating modes can be executed according to the actual charging environment. Generally, in the three-phase operating mode, in order to reduce the common mode noise of the AC side and the DC side, the center (O) of the DC side is connected to the N wire via a capacitor so that the noise is transmitted to the N wire instead of to the ground and the interference component which is transmitted to the outside of the module via the ground is reduced, in addition, a capacitor Y can be connected to the center of the DC bus to filter the noise.In single-phase operation mode, the center (O) of the DC side will form an interference source, and the capacitor will increase the common-mode noise of both the AC side and the DC side. In addition, some documents have proposed to reduce the common-mode interference in three-phase operation mode by connecting the N wire to the center of the bus, however, this will limit the PFC bus voltage regulation range, space vector control cannot be used to regulate the bus voltage in a wide range, and the N wire connection will be poorly compatible with the single-phase input. Statement of the invention

[0004] The present invention aims to propose a compatible conversion circuit single-phase and three-phase and a vehicle charger, in order to improve the fact that there are the common mode noise sources and the paths are different in three-phase charging mode and single-phase charging mode of the vehicle charger in the existing art.

[0005] In an exemplary embodiment of the present invention, a single-phase and three-phase compatible conversion circuit is provided, which comprises: a CEM module, a PFC module, a switch K1 and a control module, the CEM module being connected between wires A, B, C and N of the power grid and the PFC module, three wires A1, B1 and C1 coming out of the CEM module being connected to the PFC module, and the three wires A1, B1 and C1 being respectively connected to a virtual center provided via capacitors CX1, CX2 and CX3, the virtual center being connected to the center of the bus of the PFC module via the switch K1, and the control module being configured to detect an input signal from the power grid and control the state of the switch K1 according to the type of input signal from the power grid.

[0006] In the exemplary embodiment of the present invention, the virtual center is grounded via capacitor CY1.

[0007] In the exemplary embodiment of the present invention, when the electrical network is powered three-phase, the control module controls the switch K1 to connect it, and when the electrical network is powered single-phase, the control module controls the switch K1 to disconnect it.

[0008] In the exemplary embodiment of the present invention, the EMC module comprises an EMC filter and a switching device, the EMC filter being composed of filter units which respectively filter wires A, B, C and N, and the switching device being composed of switches arranged between wires A, B, C and N to change the state of the EMC filter.

[0009] In the exemplary embodiment of the present invention, when the power grid is powered on three-phase, the switching device puts the EMC filter in the filtering state to filter wires A, B, C and N of the power grid; and when the power grid is powered on single-phase, the switching device puts the EMC filter in the two-way filtering state.

[0010] In the exemplary embodiment of the present invention, Kl is a single-pole double-throw switch, when the power grid is powered on three-phase, the control module controls the switch Kl to connect the virtual center and the bus center of the PFC module, and when the power grid is powered on single-phase, the N wire of the power grid is output via one of the three wires A1, B1 and C1 outputting from the CEM module, and the control module controls the switch Kl to connect the virtual center and the output N wire of the CEM module.

[0011] In the exemplary embodiment of the present invention, a single-phase and three-phase compatible conversion circuit is provided, which comprises: an EMC module, a PFC module, a single-pole double-throw switch K2 and a control module, the CEM module being connected between wires A, B, C and N of the electrical network and the PFC module, three wires Al, B1 and Cl coming out of the CEM module being connected to the input phase of the PFC module, and the three wires Al, B1 and Cl being connected respectively to a virtual center provided via capacitors CX1, CX2 and CX3, the virtual center being connected to a fixed contact of the single-pole double-throw switch K2, a series freewheeling device also being arranged between the buses of the PFC module, the center of the series freewheeling device being connected to the NI wire coming out of the CEM module, a first dynamic contact of the single-pole double-throw switch K2 being connected to the center of the bus of the PFC module and a second dynamic contact of the single-pole double-throw switch K2 being connected to the N1 wire coming out of the CEM module,and the control module being configured to detect an input signal from the power grid and control the state of the single-pole double-throw switch K2 according to the type of input signal from the power grid.

[0012] In the exemplary embodiment of the present invention, the series freewheeling device comprises at least two series diodes or two series transistors.

[0013] In the exemplary embodiment of the present invention, when the electrical network is powered on three-phase, the control module controls the first dynamic contact of the single-pole double-throw switch K2 to connect it, and when the electrical network is powered on single-phase, the control module controls the second dynamic contact of the single-pole double-throw switch K2 to connect it.

[0014] In the exemplary embodiment of the present invention, the EMC module comprises an EMC filter and a switching device, the EMC filter being composed of filter units which respectively filter wires A, B, C and N, and the switching device being composed of switches arranged between wires A, B, C and N to change the state of the EMC filter.

[0015] In the exemplary embodiment of the present invention, when the power grid is powered on in three-phase, the switching device puts the EMC filter in the filtering state to filter the wires A, B, C and N of the power grid; and when the power grid is powered on in single-phase, the switching module controls the filter unit of wire A of the filter to connect it to the PFC module, or to connect the filter unit of wire A of the filter in parallel with the filter unit of wire B or the filter unit of wire C and then connect them to the PFC module, or to connect the filter unit of wire A of the filter in parallel with the filter unit of wire B and the filter unit of wire C and then connect them to the PFC module.

[0016] The present invention also provides a vehicle charger, which includes the above single-phase and three-phase compatible conversion circuit.

[0017] Compared with the prior art, when the single-phase and three-phase compatible conversion circuit of the present invention is in three-phase operation mode, the virtual center formed by the capacitors CX1 - CX3 can be short-circuited to the center of the bus via K1 to form a common mode current loop, in order to reduce the common mode noise output to the power grid, furthermore, since the voltage of the virtual center is not equal to the voltage of the N wire, space vector control can be used at the PFC stage to regulate the bus voltage in a wide range, in this case, the voltage of the virtual center generates, with respect to the voltage of the N wire, a low-frequency fluctuation of 3 times the network frequency and extremely low high-frequency noise;and in single-phase operation mode, the virtual center is disconnected at the center of the bus to isolate the common mode noise caused by the center on the DC side, in addition, single-phase filtering can be realized by changing the state of the EMC filter circuit, which can be realized with the windings of the three-phase filter, thereby improving the utilization rate of the windings and reducing the cost of components. ;

[0018] The invention can simultaneously reduce EMC noise in three-phase conversion mode and single-phase conversion mode, and regulate the PFC bus voltage in a wide range with optimized control (such as space vector control) in three-phase conversion mode, so as to optimize the performance of the entire equipment; in single-phase operation mode, input ripples can be reduced by interleaving while isolating noise, and filter components can be utilized to the maximum extent by switching the EMC filter. Brief description of the drawings

[0019] [Fig. 1] is a wiring diagram of the first single-phase and three-phase compatible conversion circuit of the exemplary embodiment according to the present invention.

[0020] [Fig.2] is a wiring diagram of a single-phase and three-phase compatible conversion circuit in three-phase mode.

[0021] [Fig.3] is a view of the voltage between the center of the bus and the N wire or ground in three-phase mode.

[0022] [Fig.4] is a view of the interference voltage between the PFC bus center and ground in single-phase mode.

[0023] [Fig.5] is a view of an exemplary switching topological structure in single-phase mode.

[0024] [Fig.6] is a view of an operating switching topological structure single-phase with two four-wire common-mode inductors.

[0025] [Fig.7] is a wiring diagram, in which an optional impedance Zsel is connected in series between the switch Kl and the center O, the virtual center is connected to a capacitor Y and Kl is a single pole double throw switch.

[0026] [Fig.8] is a view of the second single-phase and three-phase compatible conversion circuit of the exemplary embodiment according to the present invention.

[0027] [Fig.9] is a wiring diagram of the second single-phase and three-phase compatible conversion circuit of the exemplary embodiment according to the present invention in three-phase mode.

[0028] [Fig. 10] is a wiring diagram of the second single-phase and three-phase compatible conversion circuit of the exemplary embodiment according to the present invention with a switching mode in single-phase mode.

[0029] Detailed description of exemplary embodiments of the invention

[0030] [Fig.l] shows a structure of a single-phase and three-phase compatible converter circuit with a virtual center, which includes a CEM module, a PFC (Power Factor Correction) module, a neutral clamping point switch Kl, a control module and loads. The CEM module is connected between wires A, B, C and N of the power grid and the PFC module, three wires Al, B1 and Cl coming out of the CEM module corresponding to wires A, B and C are connected to the PFC module, the three wires Al, B1 and Cl are respectively connected to the virtual center 01 via capacitors CX1, CX2 and CX3, and the virtual center 01 is connected to the bus center of the PFC module via the switch KL. The control module is configured to detect an input signal from the power grid and control the state of the switch Kl according to the type of input signal from the power grid.The PFC module is configured to convert a mains current into direct current and supply power to the loads. The topological structure of the PFC module can be a three-phase two-level topological structure, or a three-phase Viennese topological structure or a three-phase buck topological structure.

[0031] Said single-phase and three-phase compatible conversion circuit can be used in a charger and the operating principle of said single-phase and three-phase compatible conversion circuit will be described below.

[0032] First, the control module collects the signals input from the power grid on the wires A, B, C and N, determines the operating mode and controls the connection of the switch K1 according to the determination. The switch K1 may also be a relay or a semiconductor switch, such as a switching circuit formed by MOS, IGBT or bidirectional thyristor, which is not limited by the present invention.

[0033] Assuming that the control module has determined that the charger is in three-phase operation mode, if Kl is not connected to the bus center and the virtual center, the high-frequency common-mode interference noise generated between the bus and ground will be transmitted to the input port via a capacitor Y or a parasitic capacitor, which makes it difficult for the power supply to pass the EMC test. To solve this problem, an example topological structure in single-phase operation mode is shown in [Fig.2], in this mode, the inductors and capacitors of the filters on wires A, B, C and N are in operation. As shown in [Fig.2], when the control module has determined that the single-phase and three-phase compatible conversion circuit is in three-phase operation mode, the control module closes the switch Kl, so that the center O on the DC bus side is connected to the virtual center 01 and the capacitor CY1.In this case, wires A1, B1, and C1 form a loop with capacitors CX1, CX2, and CX3 and the bus center capacitor, so that common-mode interference is transmitted via this low-impedance path, thereby reducing the bus noise component transmitted to the input side; in addition, capacitor CY1 absorbs common-mode noise on the DC side, thereby reducing the common-mode noise in the entire loop. In addition, since the bus center is not clamped by the N wire and all connections are made by capacitors, space vector control can be used to regulate the voltage of the DC-side capacitors within a wide range. As shown in [Fig. 3], when space vector control is used, the voltage between the O-bus center O and the N wire or ground is a low-frequency voltage, with little high-frequency signal, thereby reducing the EMC interference of the system.

[0034] When the converter is in single-phase operation mode, the voltage between the bus center and ground in single-phase rectification varies cyclically between +Vdc and -Vdc and is superimposed with an AC voltage (the voltage between the bus center and ground is shown in [Fig.4]), this voltage includes a high dv / dt noise component near the input zero crossing point. When Kl is closed (the bus center is still connected to ground via capacitor Y), the noise from the DC bus side will be coupled to ground via the virtual center, and a large interference noise will be generated, causing a serious problem for EMC.

[0035] To solve this problem, an exemplary topological structure in single-phase operation mode is shown in [Fig.5], in this mode, only the inductors and capacitors of the filters on wires A and N are in operation. In single-phase operation mode, disconnecting Kl allows disconnecting the voltage transmission path from the center of the bus to ground, which will make the EMC objective easier to achieve.

[0036] It should be noted that the EMC module comprises an EMC filter and a switching device, the EMC filter being composed of filtering units which filter wires A, B, C and N respectively, and the switching device being composed of the switches (K11, K12, K13 and K14) arranged between wires A, B, C and N to change the state of the EMC filter. The switching device may be arranged upstream of the EMC filters, or between and downstream of the EMC filters, which is not limited by the present invention.

[0037] In three-phase mode, the switching device keeps the EMC filter in four-way filtering A, B, C and N. In single-phase mode, the switching device switches the EMC filter to two-way filtering, thus allowing one-, two- or three-wire filters to operate, when the two- or three-wire filter is operating, the PFC module operates in interleaving mode, thus further reducing the input ripple current and reducing EMC interference. As shown in [Fig.5], when a three-wire filter is used in the second stage, K11, K12 and K13 are closed and K1 is open in single-phase operation. Inputs A and N enter through the filter in the first stage, phase A is filtered by two windings of the second filter through K11 and K12 and then output to the PFC module, and wire N is filtered by one winding of the second filter through K13 and then output to the PFC module.

[0038] As shown in [Fig.6], when a four-wire filter is used in the second stage of the EMC mode, K11, K12, K13 and K14 are closed and K1 is open in single-phase operation. The inputs A and N are input through the filter in the first stage, the phase A is filtered by two windings of the second filter through K11 and K12 and then output to the PFC module, and the wire N is filtered by two windings of the second filter through K13 and K14 and then output to the PFC module. In single-phase operation, all the windings of the second filter are used, so as to reduce the current of each winding, reduce the overall design cost and improve the efficiency. In addition, the corresponding modules L1 and L2 in the PFC module can operate in interleaving mode to reduce the input differential mode current.It should be noted that, the switches Kl 1 and Kl3 here can also be moved to the input port, so as to better utilize the input filter on the first stage.

[0039] As shown in [Fig.7], based on the circuit in [Fig.l], the virtual center 01 can also be grounded via the capacitor CY1, and an optional impedance Zsel can also be connected in series between the switch Kl and the center of the DC side. The switch Kl can be a single-pole double-throw switch, when the power grid is powered on three-phase, the control module controls the switch Kl to connect the virtual center and the bus center of the PFC module, and when the power grid is powered on single-phase, the N wire of the power grid is output via the Cl wires exiting the CEM module (in this case, inside the CEM module, the N wire is connected to the C wire in parallel, and the N wire is output via the Cl wire, or via the A1 or B1 wires), and the control module controls the switch Kl to connect the virtual center and the output N wire of the CEM module.

[0040] A second single-phase and three-phase compatible conversion circuit provided by the present invention is shown as [Fig.8], which comprises: a CEM module, a PFC module, a single-pole double-throw switch K2 and a control module, the CEM module being connected between wires A, B, C and N of the power grid and the PFC module, three wires A1, B1 and C1 coming out of the CEM module and corresponding to wires A, B and C of the power grid being connected to the input phase of the PFC module, and three wires A1, B1 and C1 being respectively connected to a virtual center O1 via capacitors CX1, CX2 and CX3, the virtual center being connected to a fixed contact of the single-pole double-throw switch K2, a series freewheeling device also being arranged between the buses of the PFC module, the center of the series freewheeling device being connected to wire N1 coming out of the CEM module and corresponding to wire N of the power grid,a first dynamic contact of the single-pole double-throw switch K2 being connected to the center 0 of the bus of the PFC module and a second dynamic contact of the single-pole double-throw switch K2 being connected to the wire N1 coming out of the CEM module, and the control module being configured to detect an input signal from the electrical network and control the state of the single-pole double-throw switch K2 according to the type of input signal from the electrical network.

[0041] As described above, the virtual center 01 can also be grounded via the capacitor CY1, and an impedance Zsel can also be connected in series between the switch K2 and the center of the CC side.

[0042] The series freewheeling device comprises at least two diodes in series or two transistors in series. The centers of the two diodes are directly connected to the NI wire. It should be noted that, the series freewheeling device plays a role of maintaining a current or switching, and may comprise only two diodes in series or two transistors in series. In three-phase operation, this series structure allows rectification or switching, without occupying the conversion units of L1, L2 and L3, thus enabling single-phase conversion with higher power.

[0043] [Fig.9] is a view of a three-phase input type configuration. At the three-phase input, K11, K12, K13, and K14 are all open, and K2 is set to 1. Although the NI wire is connected to the PFC output bus via a freewheeling device, the freewheeling device is not connected and is therefore equivalent to an open circuit, since the voltage only floats between the buses. This configuration can perform the same function as that of [Fig.2] and reduce EMC interference in three-phase operation.

[0044] [Fig. 10] is a single-phase input type configuration view. At the single-phase input, K11, K12, K13, and K14 are all closed, and K2 is set to 2. In this case, firstly, the PFC module can operate in interleaving mode to reduce the A-phase input differential ripple current of the EMC filter and the ripple current of the PFC DC-side capacitor. Secondly, the currents passing through across the first three wires of the L21 EMC filter are identical and equal to one-third of the single-phase input current. Therefore, this design also improves the filter utilization rate in single-phase operation, reduces component costs and improves efficiency.

[0045] It should be noted that when the power grid is energized in single phase, as shown in [Fig. 10], the switching module controls the filter unit of wire A of the filter to connect it in parallel with the filter unit of wire B and the filter unit of wire C and then connect them to the PFC module, or controls the filter unit of wire A of the filter to connect it to the PFC module or connect the filter unit of wire A of the filter in parallel with the filter unit of wire B or the filter unit of wire C and then connect them to the PFC module.

[0046] Furthermore, it should be noted that, in the exemplary embodiment of the present invention, the single-pole double-throw switch K2 can also be replaced by a single-pole single-throw switch or two switches connected between the bus center and the PFC module virtual center, and all the switches can be semiconductor switches.

[0047] In summary, the single-phase and three-phase compatible conversion circuit according to the present invention enables flexible switching between single-phase and three-phase operating modes to satisfy the requirements of different single-phase and three-phase noise sources on the filter structure, which is compatible with the reduction of EMC noise in single-phase and three-phase operating mode; and optimized control (such as space vector control) can be used in three-phase operating mode to maintain a wide output voltage adjustment range, thereby improving the performance of the converter; in addition, the switching circuit can make full use of the EMC common-mode inductance to reduce the product cost.

[0048] The exemplary embodiments below are the preferred and non-limiting exemplary embodiments, all modifications, alternative variations and improvements which respect the spirits and principles of the present invention must be included within the scope of the protection of the present invention.

Claims

Claims

1. Conversion circuit compatible with single-phase current and three-phase current, characterized in that it comprises: a CEM module, a PFC module, a switch (Kl) and a control module, the CEM module being connected between wires A, B, C and N of the electrical network and the PFC module, three wires (Al, B1, Cl) coming out of the CEM module being connected to the PFC module, and the three wires (Al, B1 and Cl) being connected respectively to a virtual center provided via capacitors (CX1, CX2, CX3), the virtual center being connected to the center of the bus of the PFC module via the switch (Kl), and the control module being configured to detect an input signal from the electrical network and control the state of the switch (Kl) according to the type of input signal from the electrical network.

2. Conversion circuit compatible with single-phase current and three-phase current according to claim 1, characterized in that the virtual center is grounded via a capacitor (CY1).

3. A conversion circuit compatible with single-phase current and three-phase current according to claim 1 or 2, characterized in that, when the electrical network is switched on three-phase, the control module controls the switch (Kl) to connect it, and when the electrical network is switched on single-phase, the control module controls the switch (Kl) to disconnect it.

4. A single-phase and three-phase current compatible conversion circuit according to claim 1 or 2, characterized in that the EMC module comprises an EMC filter and a switching device, the EMC filter being composed of filter units which filter wires A, B, C and N respectively, and the switching device being composed of switches arranged between wires A, B, C and N to change the state of the EMC filter.

5. A single-phase and three-phase compatible conversion circuit according to claim 4, characterized in that when the power grid is powered on three-phase, the switching device sets the EMC filter to the filtering state to filter wires A, B, C and N of the power grid; and when the power grid is powered on single-phase, the switching device sets the EMC filter to the two-way filtering state.

6. Conversion circuit compatible with single-phase current and current three-phase according to claim 1 or 2, characterized in that, (Kl) is a single-pole double-throw switch, when the electrical network is powered on three-phase, the control module controls the switch (Kl) to connect the virtual center and the bus center of the PFC module, and when the electrical network is powered on single-phase, the N wire of the electrical network is output via one of the three wires (Al, B1, Cl) coming out of the CEM module, and the control module controls the switch (Kl) to connect the virtual center and the output N wire of the CEM module.

7. Conversion circuit compatible with single-phase current and three-phase current, characterized in that it comprises: a CEM module, a PFC module, a single-pole double-throw switch (K2) and a control module, the CEM module being connected between wires A, B, C and N of the electrical network and the PFC module, three wires (Al, B1, Cl) coming out of the CEM module being connected to the input phase of the PFC module, and the three wires (Al, B1, Cl) being connected respectively to a virtual center provided via capacitors (CX1, CX2, CX3), the virtual center being connected to a fixed contact of the single-pole double-throw switch (K2), a series freewheeling device also being arranged between the buses of the PFC module, the center of the series freewheeling device being connected to the wire N1 coming out of the CEM module,a first dynamic contact of the single-pole double-throw switch (K2) being connected to the center of the bus of the PFC module and a second dynamic contact of the single-pole double-throw switch (K2) being connected to the N1 wire coming out of the CEM module, and the control module being configured to detect an input signal from the electrical network and control the state of the single-pole double-throw switch (K2) depending on the type of input signal from the electrical network.,

8. Conversion circuit compatible with single-phase current and three-phase current according to claim 7, characterized in that the series freewheel device comprises at least two diodes in series or two transistors in series.

9. A single-phase and three-phase compatible conversion circuit according to claim 7 or 8, characterized in that when the electrical network is powered on three-phase, the control module controls the first dynamic contact of the single-pole, double-throw switch (K2) to connect it, and when the electrical network is powered on single-phase, the control module controls the second dynamic contact of the single-pole, double-throw switch (K2) to connect it.

10. A single-phase and three-phase current compatible conversion circuit according to claim 7 or 8, characterized in that the EMC module comprises an EMC filter and a switching device, the EMC filter being composed of filter units which filter wires A, B, C and N respectively, and the switching device being composed of switches arranged between wires A, B, C and N to change the state of the EMC filter.

11. A single-phase and three-phase compatible conversion circuit according to claim 7 or 8, characterized in that when the power grid is powered on in three-phase, the switching device puts the EMC filter in the filtering state to filter the wires A, B, C and N of the power grid; and when the power grid is powered on in single-phase, the switching module controls the filter unit of wire A of the filter to connect it to the PFC module, or to connect the filter unit of wire A of the filter in parallel with the filter unit of wire B or the filter unit of wire C and then connect them to the PFC module, or to connect the filter unit of wire A of the filter in parallel with the filter unit of wire B and the filter unit of wire C and then connect them to the PFC module.

12. Vehicle charger, characterized in that it comprises a conversion circuit compatible with single-phase current and three-phase current according to any one of claims 1 to 11.

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