CN215120607U

CN215120607U - Direct current fills electric pile power topology and direct current fills electric pile

Info

Publication number: CN215120607U
Application number: CN202120527326.5U
Authority: CN
Inventors: 江冯林; 许林冲
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2021-03-10
Filing date: 2021-03-10
Publication date: 2021-12-10
Anticipated expiration: 2031-03-10

Abstract

The application discloses electric pile power topology and electric pile are filled to direct current. Should fill electric pile power topology includes: a power front-stage circuit and a power rear-stage circuit; the power pre-stage circuit comprises an AC-DC module, the input end of the AC-DC module is connected with a power grid, and the output end of the AC-DC module is connected with a direct current bus; the power post-stage circuit comprises one or more half-bridge DC-DC modules arranged in parallel and one or more post-stage controllers correspondingly connected with the half-bridge DC-DC modules, wherein the input ends of the one or more half-bridge DC-DC modules are connected with a direct current bus, and the output ends of the one or more half-bridge DC-DC modules are connected with a load through a gating switching module; and the rear-stage controller is used for performing differential pressure balance on the bus voltage of the direct-current bus and responding to the charging pile main control to open part or all of the half-bridge DC-DC modules which are correspondingly connected, wherein the charging pile main control determines the number of the half-bridge DC-DC modules to be opened according to the required power of the load.

Description

Direct current fills electric pile power topology and direct current fills electric pile

Technical Field

The embodiment of the utility model provides a relate to power technology, especially, relate to a direct current fills electric pile power topology and direct current and fills electric pile.

Background

The power topology of the charging pile tends to three-phase Vienna PFC + full-bridge/three-phase LLC, as shown in fig. 1, a three-phase incoming line is firstly connected with a front-stage PFC (PFC: power factor correction circuit) of a power module, the output of the PFC is BUS _1, BUS _2 and BUS _3, two rear-stage LLC circuits (LLC: a topological structure of a DC/DC circuit) with completely consistent parameters are respectively connected with an upper BUS (BUS _ 1-BUS _2) and a lower BUS (BUS _ 2-BUS _3) of the output of the PFC, the outputs of the two LLC circuits are connected with a series-parallel control relay module, the required charging voltage is determined according to the type of an electric vehicle, and the two LLCs are determined to work in an output series-connection state or a parallel-connection state. This topology has the following drawbacks:

the phenomenon that the upper and lower buses of the output voltage of the PFC cannot be equalized is necessarily caused, namely VBUS + ≠ VBUS-, so that the voltage equalization control of the upper and lower buses is required to be performed on a front-stage PFC circuit, the control structure of the front-stage PFC circuit is complex, the parallel current equalization and series voltage equalization effects of the output of two rear-stage LLC circuits are poor, and the service life of a charging pile is shortened.

Secondly, the system architecture that one front-stage PFC drags two rear-stage LLCs is adopted, the topology of the front-stage PFC must be a circuit with an output divided into an upper bus and a lower bus, so that the circuit topology is limited, the LLCs connected to the upper bus and the lower bus of each PFC must be used as a power unit, the two LLCs are connected in series or in parallel for output, and the power of the rear-stage LLC cannot be flexibly distributed.

And thirdly, in the current commonly used full-bridge LLC circuit or three-phase LLC circuit, because the tube bearing voltage is input voltage, and the LLC generally uses an MOS tube as a main power tube, and the MOS tube is difficult to select a proper general MOS tube for the high-voltage input occasions of 600 plus 800V, the topological structure of the full-bridge LLC or three-phase LLC is difficult to be directly connected to the whole PFC output bus.

SUMMERY OF THE UTILITY MODEL

An embodiment of the utility model provides a stake power topology and direct current charging fill electric pile are filled to the realization is to whole optimization of filling electric pile power circuit.

In a first aspect, an embodiment of the utility model provides a direct current fills electric pile power topology, include: a power front-stage circuit and a power rear-stage circuit;

the power pre-stage circuit comprises an AC-DC module, the input end of the AC-DC module is connected with a power grid, and the output end of the AC-DC module is connected with a direct current bus;

the power post-stage circuit comprises one or a plurality of half-bridge DC-DC modules arranged in parallel and one or a plurality of post-stage controllers correspondingly connected with the half-bridge DC-DC modules, wherein the input ends of the one or a plurality of half-bridge DC-DC modules are connected with the direct current bus, and the output ends of the one or a plurality of half-bridge DC-DC modules are connected with a load through a gating switching module;

the post-stage controller is used for carrying out differential pressure balance on the bus voltage of the direct-current bus and responding to a charging pile main control to open part or all of the half-bridge DC-DC modules which are correspondingly connected, wherein the charging pile main control determines the half-bridge DC-DC module to be opened and the output power of the half-bridge DC-DC module to be opened according to the required power of a load.

Optionally, the half-bridge DC-DC module is a half-bridge three-level LLC circuit.

Optionally, the half-bridge three-level LLC circuit includes: the power conversion device comprises an energy storage unit, a power conversion unit, a transformer and a resonance unit;

the first end of the energy storage unit is connected with the anode of the direct current bus, and the second end of the energy storage unit is connected with the cathode of the direct current bus;

the power conversion unit is connected in parallel with two ends of the energy storage unit;

the first end of the primary side of the transformer is connected with the first end of the resonance unit, the second end of the primary side of the transformer is connected with the midpoint of the energy storage unit, and the secondary side of the transformer is connected with a load;

the second end of the resonance unit is connected with the midpoint of the power conversion unit, so that the resonance unit is connected between the first end of the primary side of the transformer and the midpoint of the power conversion unit in series.

Optionally, the energy storage unit includes an upper bus capacitor and a lower bus capacitor;

the first end of the upper bus capacitor is used as the first end of the energy storage unit, the second end of the upper bus capacitor is connected with the first end of the lower bus capacitor, and the second end of the lower bus capacitor is used as the second end of the energy storage unit.

Optionally, the power conversion unit includes a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, which are connected in series;

the first switch tube and the second switch tube form an upper bridge arm; the third switching tube and the fourth switching tube form a lower bridge arm;

and the connection point of the second switching tube and the third switching tube is used as the midpoint of the power conversion unit.

Optionally, the power conversion unit further includes a freewheeling circuit and a flying capacitor;

the fly-over capacitor is connected with the fly-over circuit in parallel, one end of the fly-over circuit after being connected in parallel is connected between the first switch tube and the second switch tube, and the other end of the fly-over circuit is connected between the third switch tube and the fourth switch tube.

Optionally, the freewheel circuit includes a first freewheel diode and a second freewheel diode;

and the anode of the first freewheeling diode is connected with the cathode of the second freewheeling diode, and the cathode of the first freewheeling diode and the anode of the second freewheeling diode are correspondingly connected with the two ends of the flying capacitor.

Optionally, the resonant unit includes a resonant capacitor and a resonant inductor connected in series;

the first end of the resonant capacitor is connected with the midpoint of the power conversion unit, the second end of the resonant capacitor is connected with the first end of the resonant inductor, and the second end of the resonant inductor is connected with the primary side of the transformer.

Optionally, a rectifying circuit is further connected between the secondary side of the transformer and the load.

In a second aspect, the embodiment of the utility model provides a direct current fills electric pile is still provided, include the utility model discloses the direct current that arbitrary embodiment described fills electric pile power topology.

The utility model provides a direct current fills electric pile power topology uses half-bridge DC-DC module to constitute power back stage circuit, half-bridge DC-DC module can be directly with the direct current bus connection of preceding level, back stage controller can be according to bus voltage to carrying out the voltage-sharing and handling, and no longer need the preceding stage circuit to carry out the pressure difference equilibrium, from this power preceding stage circuit no longer confine the topological structure in the output area mid point, the preceding stage topology is selected more in a flexible way, thereby the circuit structure of power preceding stage circuit has been simplified. And the rear-stage controller can dynamically adjust the power state of the half-bridge DC-DC module based on load requirements according to the main control of the charging pile, so that the power rear-stage circuit can be operated in various combinations, and the flexible distribution of power is realized.

Drawings

FIG. 1 is a prior art charging pile power topology diagram;

fig. 2 is a power topology diagram of a dc charging pile according to an embodiment of the present invention;

fig. 3 is a topology diagram of a half-bridge LLC circuit according to an embodiment of the present invention;

fig. 4 is a PFC topology diagram according to an embodiment of the present invention;

fig. 5 is another PFC topology diagram according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

Fig. 2 is the embodiment of the utility model provides a direct current fills electric pile power topological diagram, this embodiment is applicable to the condition of charging to electric automobile etc. refer to fig. 2, and this direct current fills electric pile power topology and includes: a power front-stage circuit 10 and a power back-stage circuit 20;

the power front-stage circuit 10 comprises an AC-DC module 110, wherein the input end of the AC-DC module 110 is connected with a power grid, and the output end of the AC-DC module 110 is connected with a direct current bus;

the power back stage circuit 20 comprises one or more half-bridge DC-DC modules 210 arranged in parallel and one or more back stage controllers 220 correspondingly connected with the half-bridge DC-DC modules 210, wherein the input ends of the one or more half-bridge DC-DC modules 210 are connected with a direct current bus, and the output ends are connected with a load through the gate switching module 30;

the post-stage controller 220 is configured to perform voltage difference balancing on the bus voltage of the DC bus and start part or all of the half-bridge DC-DC modules correspondingly connected in response to the charging pile master control, where the charging pile master control determines the half-bridge DC-DC module to be started and the output power of the half-bridge DC-DC module to be started according to the required power of the load.

Specifically, the AC-DC module 110 is used to convert the AC power of the power grid into DC power, and output the DC power through a DC bus (as shown by a black line). The AC-DC module 110 may typically be a PFC circuit.

The DC bus at the output of the AC-DC module 110 comprises an upper bus V_BUS+And a lower bus V_BUS-Two inputs of each half-bridge DC-DC module 210 and the upper bus V_BUS+And a lower bus V_BUS-Corresponding connections, e.g. positive input terminal connected to upper bus V_BUS+The negative input end is connected with a lower bus V_BUS-The direct connection of the half-bridge DC-DC module 210 to the output bus of the power pre-stage circuit 10 is achieved.

The half-bridge DC-DC module 210 may be obtained by modifying an existing full-bridge DC-DC module. Illustratively, in the existing full-bridge DC-DC module, the semiconductor switching tubes have a double-arm structure, and the double-arm structure of the semiconductor switching tubes can be improved to a single-arm structure without increasing the number of the power switching tubes, so as to obtain the half-bridge DC-DC module 210 of the present embodiment, and obviously, the voltage borne by each power switching tube in the obtained half-bridge DC-DC module 210 during normal operation is half of the DC bus voltage.

In the power topology structure of the DC charging pile provided by this embodiment, the power front stage is composed of the AC-DC module 110, and the DC bus (V) of the output end of the AC-DC module 110_BUS+、V_BUS-) Connecting at least one half-bridge DC-DC module 210, when halfWhen the number of the bridge DC-DC modules 210 is more than one, each half-bridge DC-DC module 210 is connected in parallel and then is connected to the DC bus of the previous stage, for example, the positive input end of each half-bridge DC-DC module 210 is connected to the upper bus V of the DC bus of the previous stage_BUS+The negative input end of each half-bridge DC-DC module 210 is connected to the lower bus V of the preceding DC bus_BUS-The parallel connection of the half-bridge DC-DC modules 210 is realized.

As mentioned above, because the voltage borne by the power switch tube of the half-bridge DC-DC module 210 during normal operation is only half of the voltage of the DC bus, the half-bridge DC-DC module 210 can be directly connected to the DC bus at the output end of the front-stage AC-DC module 110, so that even in the high-voltage input situation of 600 + 800V, the power switch tube with low withstand voltage can be selected to directly connect the half-bridge DC-DC module 210 to the DC bus at the output end of the front-stage AC-DC module 110, and thus, by improving the full-bridge DC-DC module in the prior art to the half-bridge DC-DC module 210, the high withstand voltage switch tube is not required to be selected in the high-voltage input situation, thereby reducing the difficulty in type selection of the power switch tube and solving the problem of high-voltage input of the rear-stage circuit.

On the basis, because the half-bridge DC-DC module 210 can be directly connected to the DC bus of the front stage, the rear-stage controller 220 can perform voltage equalization according to the voltage difference between the upper and lower buses, and does not need to perform voltage difference equalization by the AC-DC module 110 of the front stage. This simplifies the circuit configuration of the power preceding stage circuit 10, and increases the topology selection of the power preceding stage circuit 10. For a specific principle of the voltage equalization performed by the subsequent controller 220, please refer to the description of the following embodiments.

When there are a plurality of half-bridge DC-DC modules 210, because each half-bridge DC-DC module 210 is in a parallel structure, the half-bridge DC-DC modules 210 connected to the same AC-DC module 110 can output different powers, and thus the power back-stage circuit 20 can be controlled to realize flexible power distribution. Specifically, the charging pile master controller determines the number of half-bridge DC-DC modules 210 that need to perform power output according to the required power of the load, sends a power output instruction to the half-bridge DC-DC modules 210 that need to perform power output, and the post-stage controller 220 partially or completely turns on the connected half-bridge DC-DC modules 210 in response to the charging pile master controller to perform power output. It should be noted that, in this embodiment, the charging pile master controller determines, according to a predetermined policy, the specific number of half-bridge DC-DC modules to be turned on and the specific output power of each half-bridge DC-DC module based on the power demand of the load, and then sends a power output instruction to the subsequent controller of the half-bridge DC-DC module to be turned on, so as to instruct the subsequent controller to perform specific execution, thereby implementing flexible power distribution of the power subsequent circuit.

Illustratively, each power back-stage circuit 20 includes a back-stage controller 220 and two half-bridge DC-DC modules 210, one half-bridge DC-DC module 210 has a rated power of 15KW, and the charging pile master determines the required power to be 45KW based on the load condition, as described above, the half-bridge DC-DC modules 210 connected to the same AC-DC module 110 may output different powers, that is, the half-bridge DC-DC modules 210 may be used as a basic power distribution unit to perform power distribution. The charging pile master control determines that three half-bridge DC-DC modules 210 need to be started for power output, sends a power instruction for starting all the two half-bridge DC-DC modules 210 to a first back-stage controller, sends a power instruction for starting one half-bridge DC-DC module 210 to a second back-stage controller, the first back-stage controller responds to the charging pile master control and controls all the two half-bridge DC-DC modules 210 to output through the gating switching module 30, the second back-stage controller responds to the charging pile master control and controls one half-bridge DC-DC module 210 to output through the gating switching module 30, and therefore the output power of the half-bridge DC-DC modules 210 is matched with the required power of the load. It can be seen that, in the present embodiment, each half-bridge DC-DC module 210 can independently output according to needs, so that the combination manner of the power back-stage circuit 20 is more flexible, and the flexible power distribution of the power back-stage circuit 20 is realized.

The gate switching module 30 may be, for example, a relay. The output end of the half-bridge DC-DC module 210 is connected to the load 40 through the gate switching module 30, the control end of the gate switching module 30 is connected to the post-controller 220, the post-controller 220 controls the gate switching module 30, and the connected half-bridge DC-DC module 210 is adjusted to work in a series output mode or a parallel output mode, so as to adjust different voltages and power levels.

The direct current fills electric pile power topology that this embodiment provided uses half-bridge DC-DC module to constitute power back stage circuit, and half-bridge DC-DC module can be directly be connected with preceding level's direct current bus, and back stage controller can carry out the voltage-sharing according to bus voltage to handling, and no longer need preceding stage circuit to carry out the pressure differential equilibrium, and power preceding stage circuit no longer restricts the topological structure in output area midpoint from this, and preceding stage topology selects more in a flexible way to the circuit structure of power preceding stage circuit has been simplified. And the rear-stage controller can dynamically adjust the power state of the half-bridge DC-DC module based on load requirements according to the main control of the charging pile, so that the power rear-stage circuit can be operated in various combinations, and the flexible distribution of power is realized.

Optionally, in some embodiments, the half-bridge DC-DC module is a half-bridge three-level LLC circuit. The following describes a power post-stage circuit formed by the half-bridge DC-DC module in this embodiment by taking a half-bridge three-level LLC circuit as an example.

Fig. 3 is a topology diagram of a half-bridge LLC circuit according to an embodiment of the present invention. On the basis of the above embodiment, reference is made to fig. 3. The half-bridge three-level LLC circuit comprises: the power conversion device comprises an energy storage unit, a power conversion unit, a transformer and a resonance unit;

a first end of the energy storage unit 211 is connected with a positive electrode of the direct current bus, and a second end of the energy storage unit 211 is connected with a negative electrode of the direct current bus;

the power conversion unit 212 is connected in parallel to two ends of the energy storage unit;

the first end of the primary side of the transformer T is connected with the first end of the resonance unit 213, the second end of the primary side of the transformer T is connected with the middle point of the energy storage unit 211, and the secondary side of the transformer T is connected with a load;

the second terminal of the resonance unit 213 is connected to the midpoint of the power conversion unit 212 such that the resonance unit 213 is connected in series between the first terminal of the primary side of the transformer T and the midpoint of the power conversion unit 212.

Specifically, the energy storage unit 211 may be formed by an energy storage capacitor, for example, and the energy storage unit 211 is connected to a DC bus at an output end of the AC-DC module, and is used for providing a stable bus voltage for the half-bridge three-level LLC circuit.

In some embodiments, the energy storage unit 211 includes an upper bus capacitor C1 and a lower bus capacitor C2;

the first end of the upper bus capacitor C1 is used as the first end of the energy storage unit 211, the second end of the upper bus capacitor C1 is connected to the first end of the lower bus capacitor C2, and the second end of the lower bus capacitor C2 is used as the second end of the energy storage unit 211. The voltage of the upper bus capacitor C1 is the upper bus voltage, and the voltage of the lower bus capacitor C2 is the lower bus voltage.

The control end of the power conversion unit 212 is connected to the rear-stage controller, and the power conversion unit 212 is switched on and off according to a certain logic under the action of a driving signal provided by the rear-stage controller, so that the half-bridge three-level LLC circuit is ensured to realize constant voltage/constant current output.

The resonant unit 213 realizes a resonant conversion function of the half-bridge three-level LLC circuit by a frequency modulation method.

In some embodiments, the resonance unit 213 includes a resonance capacitor Cr and a resonance inductor Lr connected in series;

a first end of the resonant capacitor Cr is connected to the midpoint of the power conversion unit 212, a second end of the resonant capacitor Cr is connected to a first end of the resonant inductor Lr, and a second end of the resonant inductor Lr is connected to the primary side of the transformer T.

Optionally, on the basis of the above embodiment, reference is continued to fig. 3. The power conversion unit 212 comprises a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4 which are arranged in series;

the first switch tube S1 and the second switch tube S2 form an upper bridge arm; the third switching tube S3 and the fourth switching tube S4 form a lower bridge arm;

the junction of the second switching tube S2 and the third switching tube S3 serves as the midpoint of the power conversion unit.

Specifically, the switching tubes in the power conversion unit 212 mainly consider the input voltage of the half-bridge, the voltage stress that the switching tubes can bear, and the conduction impedance of the switching tubes.

The four switch tubes form a straight single-bridge-arm structure. The first switch tube S1 and the second switch tube S2 form an upper bridge arm, the third switch tube S3 and the fourth switch tube S4 form a lower bridge arm, and the upper bridge arm and the lower bridge arm are alternately conducted under the action of a driving signal output by a rear-stage controller, namely two switch tubes are simultaneously conducted at the same time, so that a single switch tube only needs to bear half of bus voltage. Therefore, the voltage-withstanding requirement on the switching tubes is reduced, a half-bridge LLC circuit formed by the switching tubes with low voltage-withstanding value can be directly connected with a high-voltage direct-current bus of a front stage, high-voltage input of a rear-stage circuit is realized, the topological structure of the whole power circuit is simplified, MOS tubes are not used more, and the cost is not increased. The subsequent controller may specifically output the PWM driving signal to each switching tube through the prior art (e.g., through the driving chip), which is not described in detail in this embodiment.

Illustratively, when a direct-current bus of the AC-DC output terminal outputs a high voltage of 600V, if the upper bridge arm is turned on, the first switching tube S1 and the second switching tube S2 each need only bear a voltage of 300V, so that the half-bridge three-level LLC circuit can be ensured to operate normally. This corresponds to a reduced voltage withstand requirement for the switching tubes, so that the half-bridge LLC can be connected directly to the high-voltage dc bus of the preceding stage.

The following describes the process of performing the voltage equalizing process by the subsequent controller in this embodiment with reference to this drawing. And the post-stage controller finely adjusts the duty ratio of the upper and lower bridge arm switching tubes to carry out voltage sharing on the LLC upper and lower buses according to the pressure difference delta U of the LLC upper and lower buses. Specifically, a sampling circuit in the subsequent controller detects voltages VC1 and VC2 of an upper bus capacitor C1 and a lower bus capacitor C2 in the LLC circuit shown in fig. 3, and calculates a differential pressure Δ V ═ VC1-VC2|, and the subsequent controller performs pi operation according to the differential pressure to obtain a phase-shift duty ratio Δ D of a driving signal for the switching tube. When VC1 is greater than VC2, the duty ratio of the driving waveforms of the two switching tubes S1 and S2 of the upper half bridge arm of the LLC is D + delta D, and the duty ratio of the driving waveforms of the two switching tubes S3 and S4 of the lower half bridge arm of the LLC is D-delta D; when VC1 is less than VC2, the duty ratio of the driving waveforms of the two switching tubes S1 and S2 of the upper half bridge arm of the LLC is D-delta D, the duty ratio of the driving waveforms of the two switching tubes S3 and S4 of the lower half bridge arm of the LLC is D + delta D, the rear-stage controller outputs PWM driving signals with adjusted duty ratios to the switching tubes through a driving chip or a driving circuit and the like to realize voltage sharing of the upper bus and the lower bus of the LLC, the total effective conduction time in one period of the power switching tubes in the LLC circuit, namely D T, can not change the gain of the LLC, and the scheme is simple and reliable.

In the half-bridge LLC circuit provided in this embodiment, the power conversion unit 212 in the original full-bridge structure is improved to the half-bridge structure without increasing the number of semiconductor switching tubes, so that the operating voltage of the switching tubes is reduced to half of the input voltage, and the obtained half-bridge LLC circuit can be directly connected to the dc rectifying bus of the power front stage, thereby simplifying the circuit control of the power front stage, and even simplifying the topology of the power front stage circuit; the latter-stage controller determines the duty ratio of a driving signal of each power switch tube in the LLC circuit through the voltage difference of an upper module line and a lower module line of the LLC circuit, and voltage-sharing processing is carried out on the voltage of an upper bus and a lower bus input by the LLC circuit.

Optionally, on the basis of the above embodiment, reference is continued to fig. 3. The power conversion unit 212 further includes a freewheel circuit and a flying capacitor C_F；

Follow current circuit and flying capacitor C_FAnd one end of the parallel connection is connected between the first switch tube S1 and the second switch tube S2, and the other end is connected between the third switch tube S3 and the fourth switch tube S4.

Specifically, the follow current circuit is used for providing a follow current path for the switching tube when the upper bridge arm and the lower bridge arm are conducted and switched, and preventing reverse breakdown of the switching tube.

In some embodiments, the freewheel circuit includes a first freewheel diode D1 and a second freewheel diode D2;

the anode of the first freewheeling diode D1 is connected to the cathode of the second freewheeling diode D2, the cathode of the first freewheeling diode D1, the anode of the second freewheeling diode D2 and the flying capacitor C_FAre correspondingly connected.

Flying capacitor C_FThe junction capacitor of the switched-off switching tube can be charged when the upper bridge arm and the lower bridge arm are switched on and switched off.

The present embodiment configures the power conversion unit 212 with the freewheel circuit and the flying capacitor C_FThe upper and lower bridge arms in the power conversion unit 212 can be ensured to work normally in the switching process.

Optionally, on the basis of the above embodiment, reference is continued to fig. 3. A rectifying circuit 214 is also connected between the secondary side of the transformer T and the load.

Specifically, the rectifying circuit 214 includes a first diode D3, a second diode D4, a third diode D5, and a fourth diode D6;

the anode of the first diode D3 is connected to the cathode of the second diode D4, the cathode of the first diode D3 is connected to the cathode of the third diode D5, the anode of the third diode D5 is connected to the cathode of the fourth diode D6, and the anode of the fourth diode D6 is connected to the anode of the second diode D4;

an anode of the first diode D3 is used as a first input terminal of the rectifying circuit 214, and a cathode of the first diode D3 is used as a first output terminal of the rectifying circuit 214;

the cathode of the fourth diode D6 serves as a second input terminal of the rectifying circuit 214, and the anode of the fourth diode D6 serves as a second output terminal of the rectifying diode.

Optionally, on the basis of the above embodiment, the AC-DC module in this embodiment is a PFC circuit with a midpoint at the output end or a PFC circuit without a midpoint at the output end.

Specifically, in this embodiment, a half-bridge three-level LLC circuit is used as a power back-stage circuit, and the back-stage controller can fine-tune the duty ratios of the upper and lower bridge arm switching tubes according to the voltage difference between the upper and lower buses on the input side of the half-bridge LLC circuit to maintain the voltage balance between the upper and lower buses on the input side under steady-state operation, so that there is no need to perform voltage-sharing control on the upper and lower buses by using a front-stage PFC circuit, and the front-stage AC-DC module may be a PFC circuit with a midpoint at the output end or a PFC circuit without a midpoint at the output end.

In some embodiments, the power front-stage circuit is embodied in a topology without a midpoint of a dc-side output represented by a three-phase six-switch PFC circuit as shown in fig. 4, or a topology with a midpoint of a dc-side output represented by a three-level vienna PFC circuit as shown in fig. 5. Therefore, the half-bridge three-level LLC circuit is used as the power back-stage circuit, the circuit structure of the power front-stage circuit is simplified, and the topology of the power front-stage circuit is expanded.

Meanwhile, each LLC circuit is connected to the whole PFC output bus to work, output series-parallel connection of the LLC circuit does not need to be limited like a traditional charging pile power module, and power distribution is easy to achieve. Taking a charging pile for double-gun charging as an example, the LLC module power from the same PFC bus can be distributed to different charging guns without considering the voltage-sharing problem of the upper bus and the lower bus of the PFC bus. The following is a detailed description with reference to examples.

As an example, taking a 30KW charging pile power module as an example, the traditional structure is a 30KW PFC + two 15KW LLC circuits, where the two LLC circuits are input series-connected to the whole PFC bus, as shown in fig. 1, and in this topology, the two LLC circuits must output the same power all the time, so that the two LLC circuits cannot be allocated to different charging guns. However, after the power structure shown in fig. 2 is adopted, two 15KW LLC circuits are connected in parallel to the PFC whole bus, and their output powers may be inconsistent, so that two LLC circuits connected to the same PFC whole bus can be assigned to different charging guns.

If two charging guns (gun a and gun B) each require 15KW of output power, according to the power structure of fig. 1, two different power modules must be started to be respectively allocated to gun a and gun B, each charging module only outputs 15KW, and the charging module will reach the optimal operating point at the rated power (in this case, 30KW) at the beginning of the design, obviously, allocating power according to the power structure of fig. 1 will make each power module not reach the optimal operation. However, if according to the power structure of fig. 2, only one power module needs to be started, one 15KW LLC is allocated to gun a, and the other 15KW LLC is allocated to gun B, so that the number of opened power modules is small, each power module can work at the optimal working point, and the charging efficiency of the charging pile is greatly improved.

As an example, taking a 120KW two-gun charging pile as an example (one 120KW charging pile includes 4 30KW charging modules, each charging module includes two LLCs), if gun a and gun B are respectively connected to an electric vehicle with a rated charging power of 75KW and an electric vehicle with a rated charging power of 45KW, according to a conventional power structure, gun a and gun B can only be allocated to two charging modules of gun a and two charging modules of gun B, and gun a cannot meet the full power requirement of the vehicle at this time, and can only charge with reduced power; or three charging modules are distributed to the gun A and one charging module is distributed to the gun B, and the gun B cannot meet the full-power requirement of the automobile at the moment. However, if the power structure of this embodiment is adopted, the LLC power can be distributed to two power modules of the gun a, one power module of the gun B, and then one LLC of the remaining power module is distributed to the gun a, and the other LLC is distributed to the gun B, so that the gun a and the gun B can both meet the full power charging requirement of the electric vehicle.

Optionally, on the basis of the above-mentioned embodiment, the embodiment of the utility model provides a direct current fills electric pile is still provided, and this direct current fills electric pile and includes the direct current that any above-mentioned embodiment described and fill electric pile power topology, therefore the direct current that this embodiment provided fills electric pile and also includes the beneficial effect that any above-mentioned embodiment described.

It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.

Claims

1. A dc charging post power topology, comprising: a power front-stage circuit and a power rear-stage circuit;

2. The DC charging post power topology of claim 1, wherein the half-bridge DC-DC module is a half-bridge three-level LLC circuit.

3. The dc charging post power topology of claim 2, wherein the half-bridge tri-level LLC circuit comprises: the power conversion device comprises an energy storage unit, a power conversion unit, a transformer and a resonance unit;

4. The DC charging post power topology of claim 3, wherein the energy storage unit comprises an upper bus capacitor and a lower bus capacitor;

5. The DC charging post power topology of claim 3, wherein the power conversion unit comprises a first switching tube, a second switching tube, a third switching tube and a fourth switching tube which are arranged in series;

6. The dc charging post power topology of claim 5, wherein the power conversion unit further comprises a freewheeling circuit and a flying capacitor;

7. The dc charging post power topology of claim 6, wherein the freewheeling circuit comprises a first freewheeling diode and a second freewheeling diode;

8. The DC charging post power topology of claim 3, wherein the resonant unit comprises a resonant capacitor and a resonant inductor in series;

9. The DC charging post power topology of claim 3, wherein a rectifying circuit is further connected between the secondary side of the transformer and the load.

10. The DC charging post power topology of any one of claims 1-9, wherein the AC-DC module is a PFC circuit with a midpoint at an output or a PFC circuit without a midpoint at an output.

11. A dc charging post comprising the dc charging post power topology of any of claims 1-10.