Bidirectional charging pile, power converter and capacitor front-end circuit thereof

Abstract

The utility model discloses a bidirectional charging pile, a power converter and a capacitor front-end circuit thereof, and relates to the technical field of power electronics. According to the capacitor front-end circuit, an access switch connected with a corresponding power supply is arranged for a capacitor in a power converter so as to realize connection and disconnection between the capacitor and the corresponding power supply; moreover, the access switch is also connected in parallel with a first controllable semiconductor device, and when a fault occurs and the access switch needs to be switched off, the first controllable semiconductor device can be switched on, so that the access switch is controlled to be switched off when the first controllable semiconductor device is in a switched-on state, and furthermore, no voltage peak exists when the access switch is switched off. And meanwhile, the model selection difficulty of the access switch can be reduced, and the increase of the device model selection cost is avoided. Moreover, the capacitor front-end circuit can also realize device multiplexing of a slow start circuit and a bleeder circuit, and the circuit complexity and the overall cost of the system are reduced.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and particularly to a bidirectional charging pile, a power converter and a capacitive front-end circuit thereof. Background Art

[0002] In a power converter, a large number of capacitors are usually used to achieve voltage stabilization and filtering effects; in order to control the power-on timing, an access switch needs to be added at the front end of the capacitor to control the access switch to close when power-on is required, so that the capacitor receives the electric energy provided by the front-end power supply.

[0003] In addition, in the event of a fault, the loop can also be cut off by controlling the disconnection of the access switch; however, since there is a voltage on the capacitor under normal operating conditions, an arcing phenomenon will occur during this disconnection process, reducing the service life of the access switch. Summary of the Utility Model

[0004] In view of the above problems, the present application provides a bidirectional charging pile, a power converter and a capacitive front-end circuit thereof to achieve disconnection protection for the access switch while avoiding increasing the device selection cost. The specific solutions are as follows:

[0005] In a first aspect of the present application, a capacitive front-end circuit of a power converter is provided. The power converter includes at least one capacitor, and the capacitor is connected to a corresponding power supply through the capacitive front-end circuit. The capacitive front-end circuit includes: an access switch and a first controllable semiconductor device; wherein,

[0006] The access switch is arranged in a transmission branch between the capacitor in the power converter and the corresponding power supply;

[0007] The first controllable semiconductor device is connected in parallel with the access switch;

[0008] Wherein, the access switch is controlled to disconnect when the first controllable semiconductor device is in a conducting state.

[0009] In a possible implementation, the capacitive front-end circuit of the power converter further includes: a resistor branch;

[0010] The resistor branch is connected in parallel with the first controllable semiconductor device.

[0011] In a possible implementation, the resistor branch includes: a resistor, or at least two resistors connected in series and parallel.

[0012] In a possible implementation, the capacitive front-end circuit of the power converter further includes: a second controllable semiconductor device;

[0013] The second controllable semiconductor device is connected in series with at least one resistor in the resistor branch to form a discharge circuit for the capacitor.

[0014] In a possible implementation, the second controllable semiconductor device and the first controllable semiconductor device are integrated in the same module.

[0015] In a possible implementation, the capacitor front-end circuit of the power converter further includes: an anti-reverse device;

[0016] One end of the anti-reverse device is connected to one end of the access switch close to the power supply;

[0017] The other end of the anti-reverse device is connected to one end of the access switch close to the capacitor through a parallel branch formed by the first controllable semiconductor device and the resistor branch.

[0018] In a possible implementation, the anti-reverse device is: a diode or a switching tube.

[0019] In a possible implementation, when the power supply is a DC power supply, the access switch is arranged in the positive transmission branch between the capacitor and the corresponding power supply.

[0020] In a possible implementation, the capacitor front-end circuit of the power converter further includes: another access switch arranged in the negative transmission branch between the capacitor and the corresponding power supply.

[0021] In a possible implementation, the capacitor front-end circuit of the power converter further includes: a fusing device arranged between the access switch and the corresponding power supply.

[0022] In a possible implementation, the access switch is: a circuit breaker, a relay or a contactor.

[0023] The second aspect of the present application provides a power converter, including: a main circuit, at least one capacitor and a corresponding capacitor front-end circuit; wherein,

[0024] At least one side of the main circuit is provided with the capacitor;

[0025] The capacitor is connected to the corresponding power supply through the corresponding capacitor front-end circuit;

[0026] The capacitor front-end circuit is the capacitor front-end circuit of the power converter as described in the first aspect or any implementation form of the first aspect above.

[0027] In a possible implementation, the main circuit is a bidirectional or unidirectional DC / DC conversion circuit or a DC / AC conversion circuit;

[0028] Alternatively, the main circuit is an AC / DC conversion circuit or an AC / AC conversion circuit that performs bidirectional or unidirectional conversion.

[0029] The third aspect of this application provides a bidirectional charging pile, including: a power converter as described in the second aspect above or any implementation form of the second aspect;

[0030] One side of the main circuit in the power converter is used to connect to the power battery of the electric vehicle.

[0031] In a possible implementation, the main circuit includes at least one bidirectional DC / AC conversion circuit. The DC side of the bidirectional DC / AC conversion circuit is used to connect to the power battery, and the AC side of the bidirectional DC / AC conversion circuit is used to connect to the power grid.

[0032] By means of the above technical solution, the capacitor front-end circuit of the power converter provided in this application sets an access switch for connecting the corresponding power supply to the capacitor in the power converter to achieve the connection and disconnection between the capacitor and the corresponding power supply; moreover, a first controllable semiconductor device is connected in parallel to the access switch. When a fault occurs and the access switch needs to be disconnected, the first controllable semiconductor device can be turned on first, so that the access switch is controlled to disconnect when the first controllable semiconductor device is in the on state. Furthermore, when the access switch is disconnected, there will be no voltage spike, avoiding the generation of arcing phenomenon. At the same time, the selection difficulty of the access switch can be reduced, and the device selection cost can be avoided from increasing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Combined with the drawings and referring to the following specific embodiments, the above and other features, advantages, and aspects of the various embodiments of the present disclosure will become more obvious. Throughout the drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic, and the original components and elements are not necessarily drawn to scale.

[0034] Figure 1 A schematic diagram of the connection structure on the battery side of a power converter provided by the prior art;

[0035] Figure 2 A schematic diagram of a structure of the capacitor front-end circuit in the power converter provided by this application;

[0036] Figure 3 Another schematic diagram of the structure of the capacitor front-end circuit in the power converter provided by this application;

[0037] Figure 4 Another schematic diagram of the structure of the capacitor front-end circuit in the power converter provided by this application;

[0038] Figure 5 Another schematic diagram of the structure of the capacitor front-end circuit in the power converter provided by this application;

[0039] Figure 6 Another structural schematic diagram of the capacitor front-end circuit in the power converter provided by the present application;

[0040] Figure 7 Another structural schematic diagram of the capacitor front-end circuit in the power converter provided by the present application;

[0041] Figure 8 Another structural schematic diagram of the capacitor front-end circuit in the power converter provided by the present application;

[0042] Figure 9 Another structural schematic diagram of the capacitor front-end circuit in the power converter provided by the present application;

[0043] Figure 10 Another structural schematic diagram of the capacitor front-end circuit in the power converter provided by the present application;

[0044] Figure 11 Another structural schematic diagram of the capacitor front-end circuit in the power converter provided by the present application. Detailed implementation manners

[0045] The embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application. The terms used in the implementation manners part of the present application are only used to explain the specific embodiments of the present application, rather than aiming to limit the present application.

[0046] The embodiments of the present application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention. Those of ordinary skill in the art know that with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0047] The terms "first", "second", etc. in the description and claims of the present application and the above accompanying drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances, which is only a way of distinguishing objects with the same attributes when describing the embodiments of the present application. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, so that a process, method, system, product or device including a series of units does not have to be limited to those units, but may include other units not clearly listed or inherent to these process, method, product or device.

[0048] Figure 1 The figure shows a schematic diagram of the battery side structure of a power converter such as a bi-directional DC / DC converter or a bi-directional DC / AC converter connected to a battery in the prior art. A large capacitor C1 is provided on the battery side of the power converter to store and filter the electrical energy on this side. By controlling the on / off states of two access switches CB1 and CB2, the control of whether the circuit between the battery and the main circuit of the power converter is connected can be achieved. The existence of these two access switches CB1 and CB2 can effectively isolate the battery from the inside of the power converter and prevent electric shock. However, due to safety regulations and the special requirement that these two access switches need to be able to extinguish arcs when disconnected, these two access switches are often relatively expensive. Even in the case of lower safety regulation requirements, although the access switch CB1 in the negative transmission branch can be removed, the other access switch CB2 in the positive transmission branch will still have a high selection cost because it needs to have the function of disconnecting and extinguishing arcs.

[0049] Therefore, the application embodiment provides a capacitor front-end circuit of a power converter to achieve the disconnection protection of the access switch and avoid increasing the device selection cost at the same time. The specific solution is as follows:

[0050] See Figure 2 , the power converter includes at least one ( Figure 2 shown as an example with one in

[0051] The access switch CB2 is arranged in the transmission branch between the capacitor C1 and the corresponding power supply. When the power supply is a DC power supply such as a battery, the access switch CB2 is arranged in the positive transmission branch between the capacitor C1 and the corresponding power supply, which can meet the basic safety regulations.

[0052] The first controllable semiconductor device Q1 is connected in parallel with the access switch CB2. Moreover, due to the existence of the first controllable semiconductor device Q1, when the access switch CB2 needs to be disconnected, the first controllable semiconductor device Q1 can be closed first, so that the voltage difference across the access switch CB2 is very small, and then the access switch CB2 can be controlled to disconnect. As a result, there will be no voltage spike when the access switch CB2 is disconnected, which can effectively protect the access switch CB2 and extend its service life. And without the above-mentioned arc extinguishing function required for the access switch CB2, the selection difficulty of the access switch CB2 can be reduced, and the increase in selection cost can be avoided.

[0053] That is, in this embodiment, the access switch CB2 is set to be controlled to disconnect when the first controllable semiconductor device Q1 is in the on state; in practical applications, the controller in the power converter can be used to control the on / off states of the access switch CB2 and the first controllable semiconductor device Q1, as Figure 3 shown; when the power converter shuts down or fails, its controller will control the first controllable semiconductor device Q1 to close immediately and then disconnect the access switch CB2, thereby effectively protecting the access switch CB2 and reducing the difficulty of selecting the access switch CB2.

[0054] It can be understood that the connection between the controller and the controllable semiconductor device and the switch can be a physical circuit connection or a wireless connection. After connection, the controller can control the on / off states of the controllable semiconductor devices (including Q1 and Q2) and the switches (including CB1 and CB2).

[0055] The capacitor front-end circuit 10 of the power converter provided in this embodiment sets an access switch CB2 for connecting the corresponding power supply to the capacitor C1 in the power converter to achieve the connection and disconnection between the capacitor C1 and the corresponding power supply; moreover, a first controllable semiconductor device Q1 is also connected in parallel with the access switch CB2. When it is necessary to disconnect the access switch CB2 in case of a fault, the first controllable semiconductor device Q1 can be turned on first, so that the access switch CB2 is controlled to disconnect when the first controllable semiconductor device Q1 is in the on state. Furthermore, when the access switch CB2 disconnects, there will be no voltage spike, avoiding the generation of arcing. At the same time, the access switch CB2 does not need to have an arc extinguishing function, which can reduce the difficulty of selecting the access switch CB2 and avoid increasing the device selection cost. In addition, in high-voltage and high-power application scenarios, it can also avoid Figure 1 the problem of the large volume of the access switch CB2 in the prior art shown.

[0056] It should be noted that when the power supply is a DC power supply, in the face of relatively high safety regulations requirements, the capacitor front-end circuit 10 may further include Figure 2 and Figure 3As shown in the figure: Another access switch CB1 is disposed in the negative transmission branch between the capacitor C1 and the corresponding power supply. When the power converter shuts down or fails, its controller first controls the first controllable semiconductor device Q1 to close, and then disconnects the access switch CB2, thereby achieving effective protection for the access switch CB2; then, the access switch CB1 and the first controllable semiconductor device Q1 can be controlled to disconnect. In practical applications, the first controllable semiconductor device Q1 can be controlled to disconnect first to cut off the loop between the power supply and the power converter, making the current on the loop zero, and then the access switch CB1 can be controlled to disconnect, thereby achieving protection for the access switch CB1; at the same time, the selection difficulty of both the access switches CB1 and CB2 can be reduced. For example, a relay without arc extinguishing ability can be selected, etc.

[0057] In practical applications, the access switches CB1 and CB2 can be circuit breakers, relays or contactors, etc. As long as their selection costs are lower than those of the prior art, it can be determined according to their specific application environments, and all are within the protection scope of this application.

[0058] In addition, as Figure 2 and Figure 3 shown in the figure, the capacitor front-end circuit 10 may further include: a fusing device, such as a fuse F1, disposed between the access switch CB2 and the corresponding power supply to achieve the protection function of overcurrent fusing.

[0059] It should be noted that in the prior art, when a power converter is connected to a load with a power supply function such as a battery, referring to Figure 1 , when the power converter is initially powered on, in the case of a large capacitance value of the capacitor C1, since the voltage of the battery will be instantaneously applied to the capacitor C1, a large current will appear when the access switches CB1 and CB2 are closed, which easily causes the access switches CB1 and CB2 to fail. Therefore, a soft-start resistor R1 and R2 need to be added on the battery side to reduce this instantaneous large current. The prior art usually adds a soft-start switch CB3 connected in series with the soft-start resistors R1 and R2, so that the battery is smoothly connected to the battery side to prevent a large current from occurring and damaging the access switches CB1 and CB2.

[0060] Referring to Figure 4 (the controller and its signal lines are not shown), the capacitor front-end circuit 10 provided in this embodiment removes the soft-start switch CB3 in the prior art, and on the basis of the structure shown in Figure 2 , a resistor branch 101 is added; the resistor branch 101 is connected in parallel with the first controllable semiconductor device Q1, that is, in parallel with the access switch CB2.

[0061] In practical applications, the resistor branch 101 may include: a resistor, or at least two resistors connected in series and parallel.Figure 5 Taking the example that the resistor branch 101 includes two resistors connected in series (R01 or R02 as shown in the figure), that is, in the resistor branch 101, it may include only one resistor or multiple resistors. Moreover, when multiple resistors are included, the series-parallel relationship between the resistors is not limited and can be determined according to its application environment, all of which are within the protection scope of this application.

[0062] When the power converter is connected to a load such as a battery with a power supply function, refer to Figure 4 , when the power converter is initially powered on, first control the access switch CB1 in the negative transmission branch to close. At this time, due to the existence of the resistor branch 101, the large current that appears when the access switch CB1 operates can be reduced. For the circuit structure that does not require the access switch CB1, this step of controlling the access switch CB1 to close is not required, and it can be directly connected to the battery-like load.

[0063] When the voltage on the capacitor C1 meets certain conditions, which can be that the controller detects that the voltage rises to a predetermined voltage, or determines that the difference between the voltage and the battery voltage shrinks to a preset fixed value, or determines that a fixed time has elapsed after power-on, the controller can control the access switch CB2 to close, so that the access switch CB2 closes when the voltage difference across it is small, and its closing action will not have a spike voltage and large current, and safe closing can be achieved. In addition, after the access switch CB2 closes, it will bypass the resistor branch 101, so that the current can directly flow through the access switch CB2, which can save a soft-start switch CB3 compared with the prior art.

[0064] That is, in this embodiment, the access switch CB2 can not only be used as a disconnecting switch to disconnect the loop between the power converter and the power supply, but also be used as a switch with a soft-start function. The function of the soft-start circuit can be realized only through the resistor branch 101, further reducing the cost.

[0065] It is also worth noting that in the prior art, when the power converter is shut down, refer to Figure 1 , since the voltage in the capacitor C1 cannot be instantaneously reduced, a discharge resistor R3 and a discharge switch Q need to be added, and the electric quantity in the capacitor C1 is consumed in the resistor R3 by closing the discharge switch Q. However, as Figure 1 shown in the figure, the functions of its soft-start circuit and discharge circuit are independent, and many components are added and cannot be reused.

[0066] Therefore, on the basis of the above embodiment, this embodiment provides another capacitor front-end circuit 10, refer to Figure 6 (in Figure 5For example, on the basis of Figure 6 as shown in Figure 7 R02 or

[0067] See Figure 6 When the resistance branch 101 includes two resistors R01 and R02 connected in series, the second controllable semiconductor device Q2 is connected in series with the capacitor C1 through the resistor R02; see Figure 7 When the resistance branch 101 includes only one resistor R01, the second controllable semiconductor device Q2 is connected in series with the capacitor C1 through the resistor R01.

[0068] When the power converter shuts down and the main circuit stops operating, its controller can control the second controllable semiconductor device Q2 to close, and discharge the electrical energy on the capacitor C1 through Figure 6 the resistor R02 as shown in Figure 7 or the resistor R01 as shown in

[0069] That is, in this embodiment, by borrowing the corresponding resistor in the soft-start circuit (such as Figure 6 R02 as shown in Figure 7 or R01 as shown in

[0070] ), a discharge circuit is formed with the second controllable semiconductor device Q2, thereby realizing the reuse of some devices in the soft-start circuit and the discharge circuit, improving the device reuse rate, and reducing the overall system cost and circuit complexity. Figure 7 When the resistance branch 101 includes only one resistor (as shown in Figure 6 ), the soft-start circuit and the discharge circuit will reuse all the resistors in the resistance branch 101; when the resistance branch 101 includes at least two resistors, and these resistors can be divided into at least two series-connected parts, such as Figure 6 the situation shown in

[0071] only at least one of the resistors needs to be reused in the soft-start circuit and the discharge circuit, such as Figure 8, the second controllable semiconductor device Q2 can be integrated with the first controllable semiconductor device Q1 in the same module S to realize the sharing of the two controllable semiconductor devices Q1 and Q2; in addition, at this time, only one resistor R01 can be provided in the resistor branch 101, or multiple resistors can be connected in series and parallel (not shown in the figure), which are all within the protection scope of this application.

[0072] Based on the above embodiments, this embodiment provides another capacitive front-end circuit 10. Refer to Figure 8 or Figure 9 (taking Figure 6 as an example for display), the capacitive front-end circuit 10 further includes: an anti-reverse device 102; one end of the anti-reverse device 102 is connected to one end of the access switch CB2 close to the power supply; the other end of the anti-reverse device 102 is connected to one end of the access switch CB2 close to the capacitor C1 through a parallel branch composed of the first controllable semiconductor device Q1 and the resistor branch 101; moreover, when the anti-reverse device 102 is turned on, electric energy is transmitted from one end of the access switch CB2 close to the power supply to one end of the access switch CB2 close to the capacitor C1.

[0073] In practical applications, the anti-reverse device 102 can be the diode D1 shown in the figure, or a switching tube can also be used, which is not limited here and can be determined according to its specific application environment, and all are within the protection scope of this application. As Figure 8 or Figure 9 shown, when the anti-reverse device 102 is arranged in the positive transmission branch, the current when the anti-reverse device 102 is turned on will flow from one end of the access switch CB2 close to the power supply to one end of the access switch CB2 close to the capacitor C1.

[0074] Taking Figure 9 as an example for illustration, the DC side of the main circuit of the power converter is incorporated into the capacitor C1 and is connected to the power supply through the access switches CB1 and CB2 and the fuses F1. The diode D1 is divided into two paths. One path is connected in series with the resistors R01 and R02 and is at both ends of the access switch CB2. The other path is connected in series with the first controllable semiconductor device Q1 and is at both ends of the access switch CB2. The connection midpoint of the resistors R01 and R02 is connected to the second controllable semiconductor device Q2, and the other end of the second controllable semiconductor device Q2 is connected to the negative end of the capacitor C1.

[0075] Compared with the previous embodiments, Figure 9After adding the diode D1, when the power converter is connected to a load with a power supply function such as a battery, especially when the power converter operates in reverse and charges the battery, its controller will control the voltage on the battery side of the main circuit to increase. When this voltage increases to meet certain conditions with the battery voltage, that is, when the voltage difference across the access switch CB2 is small, the access switch CB2 can be closed. Furthermore, when the power converter operates in reverse and connects to the battery, it no longer needs to pass through the resistor branch 101, avoiding unnecessary power consumption.

[0076] In addition, the diode D1 can not only achieve the above anti-reverse function, but also provide a freewheeling function during soft start and cooperate with the first controllable semiconductor device Q1 to achieve a clamping effect during a fault. Specifically:

[0077] When the power converter is powered on, first control the access switch CB1 in the negative transmission branch to close. At this time, due to the action of the diode D1 and the resistor branch 101, the large current that appears when the access switch CB1 operates can be reduced. When the voltage on the capacitor C1 meets certain conditions and the voltage difference across the access switch CB2 is small, the controller can control the access switch CB2 in the positive transmission branch to close, and its closing action will not have a spike voltage and large current.

[0078] When shutting down or a fault occurs, the controller first controls the first controllable semiconductor device Q1 to conduct, and clamps the voltage difference across the access switch CB2 through the diode D1 and the first controllable semiconductor device Q1, making the voltage difference across the access switch CB2 very small. Then control the access switch CB2 to disconnect. Furthermore, the access switch CB2 can be disconnected when the voltage difference on both sides is very small, so there is no voltage spike when it disconnects, avoiding the generation of arcing phenomena, improving its service life, and at the same time reducing the selection difficulty of the access switch CB2 and avoiding increasing the device selection cost.

[0079] Figure 10 It is the structural diagram when saving the access switch CB1 in the negative transmission branch under the basic safety regulations requirements. It only reduces the closing control of the access switch CB1 by the controller during soft start, and other control processes are the same as the above content and will not be elaborated.

[0080] This embodiment not only solves the pain point that directly disconnecting the access switch will affect its life when an abnormality occurs, but also greatly reduces the selection difficulty of the access switch. Under the condition of meeting the functions, it can achieve a significant reduction in the overall cost.

[0081] Another embodiment of the present application also provides a power converter, as Figures 2 to 10 shown in any of the accompanying drawings, which includes: a main circuit, at least one capacitor C1 and a corresponding capacitor front-end circuit 10; where:

[0082] At least one side of the main circuit is provided with a capacitor C1; Figures 2 to 10 In the following, the example where the capacitor C1 is provided on the DC side of the main circuit is used for demonstration.

[0083] The capacitor C1 is connected to the corresponding power supply through the corresponding capacitor front-end circuit 10; the capacitor front-end circuit 10 is the capacitor front-end circuit 10 described in any of the above embodiments. The structure and working principle of the capacitor front-end circuit 10 can be referred to the above embodiments and will not be elaborated here one by one.

[0084] In practical applications, the main circuit can be a bidirectional or unidirectional DC / DC conversion circuit, DC / AC conversion circuit, AC / DC conversion circuit or AC / AC conversion circuit; for example:

[0085] When the main circuit is a bidirectional DC / DC conversion circuit or a bidirectional DC / AC conversion circuit, the power supply connected to its DC side through the corresponding capacitor front-end circuit 10 is a DC power supply, and the DC power supply can specifically be a battery. At this time, the power converter can be a PCS or a bidirectional charging pile, etc.

[0086] Alternatively, when the main circuit is a DC / DC conversion circuit or a DC / AC conversion circuit, the DC power supply connected to its DC side through the corresponding capacitor front-end circuit 10 can be a photovoltaic string. At this time, the power converter can be a photovoltaic inverter. For the case where the power supply is a photovoltaic string, the anti-reverse device 102 can be selected or deleted according to the actual application situation, which is within the protection scope of this application. In addition, the two controllable semiconductor devices Q1 and Q2 used at this time can be (Insulate-Gate Bipolar Transistor) or MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). Here are only two optional examples and are not limited to this. It can be determined according to its specific application environment, which is within the protection scope of this application.

[0087] Furthermore, when the main circuit is a bidirectional or unidirectional AC / DC conversion circuit or AC / AC conversion circuit, the power supply connected to its AC side through the corresponding capacitor front-end circuit 10 is an AC power supply, such as the power grid. At this time, the power converter can be a rectifier, etc. When the AC power supply is a three-phase power grid, access switches CB2, the first controllable semiconductor device Q1 and the resistor branch 101 can be respectively provided on each phase line; or, as shown in Figures 2 to 10 shown, the access switches CB2, the first controllable semiconductor device Q1 and the resistor branch 101 can be respectively provided on two of the phase lines; or, as shown in Figure 11 shown, the access switches CB2, the first controllable semiconductor device Q1 and the resistor branch 101 can be respectively provided on two of the phase lines; Figures 2 to 10The access switch CB2, the first controllable semiconductor device Q1, and the resistor branch 101 shown in [Figure], and only the access switch CB1 shown in [Figure] is provided on the phase line of the last phase. At this time, the power-on soft start when connecting to the three-phase power grid can also be realized through two soft start circuits. It should be noted that since it is necessary to conduct alternating current, the first controllable semiconductor device Q1 used here needs to be a device that can conduct current bidirectionally, such as a MOSFET, etc.; moreover, since the capacitance of the AC side is generally small and there is no need to borrow a soft start circuit for discharging, the Figures 2 to 10 second controllable semiconductor device Q2 shown in [Figure] can be omitted, and only one resistor needs to be provided in the resistor branch 101. In addition, since the alternating current has positive and negative half-cycles, the reverse protection device 102 in the above figures can be omitted. Figures 2 to 10 The power converter provided in this embodiment can add the above capacitor front-end circuit 10 between the capacitor on its DC side and / or AC side and the corresponding power supply, which can enable the power converter to have the ability to instantaneously disconnect from any side power supply, and provide a clamping protection function for the access switch during abnormal disconnection, prevent the access switch from arcing, improve the service life of the access switch, and can reduce the selection difficulty and cost of the access switch; it can also achieve soft start during power-on, discharge during shutdown, and reuse the devices of the soft start circuit and the discharge circuit, reducing the circuit complexity and the overall system cost.

[0088] Another embodiment of the present application also provides a bidirectional charging pile, including: the power converter as described in the above embodiment; the main circuit in the power converter, one side of which is used to connect the power battery of the electric vehicle.

[0089] In practical applications, the main circuit may include at least one bidirectional DC / AC conversion circuit; when the number of the bidirectional DC / AC conversion circuits is greater than 1, the bidirectional DC / AC conversion circuits are connected in parallel; moreover, the DC side of the bidirectional DC / AC conversion circuit is used to connect the power battery of the electric vehicle, and the AC side of the bidirectional DC / AC conversion circuit is connected to the power grid; that is, the power supply connected to the DC side of the bidirectional charging pile is the power battery of the electric vehicle, and the power supply connected to the AC side is the power grid.

[0090] For the main circuit that performs power conversion in the bidirectional charging pile, its specific structure can refer to the prior art; in particular, the circuit structure that can realize adjustable charging power, and the circuit structure that can realize V2G (Vehicle to Grid), etc. are all within the protection scope of the present application. In addition, in the V2G application scenario, the presence of the above reverse protection device 102 can avoid unnecessary power loss caused by passing through the resistor branch 101 when the bidirectional charging pile charges the battery vehicle.

[0091] ​

[0092] For other structures and working principles of the power converter in this bidirectional charging pile, reference can be made to the above embodiments, which will not be elaborated one by one here.

[0093] By adding the above-mentioned capacitor front-end circuit between the capacitor on the DC side and / or AC side of the main circuit of this bidirectional charging pile and the corresponding power supply, the power converter can be enabled to have the ability to instantaneously disconnect from any side power supply, and provide a clamping protection function for the access switch during abnormal disconnection, prevent the access switch from arcing, improve the service life of the access switch, reduce the selection difficulty and cost of the access switch; it can also achieve soft start when powering on, discharge when shutting down, and reuse the devices of the soft start circuit and the discharge circuit, reducing the circuit complexity and the overall system cost.

[0094] For the same or similar parts among the various embodiments in this specification, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for a system or a system embodiment, since it is basically similar to the method embodiment, the description is relatively simple. For the relevant parts, reference can be made to the partial description of the method embodiment. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0095] Those skilled in the art can further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0096] With respect to the above description of the disclosed embodiments, the features described in each embodiment in this specification may be replaced or combined with each other, enabling those skilled in the art to implement or use the present utility model. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present utility model. Therefore, the present utility model will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A capacitor front-end circuit of a power converter, characterized in that: The capacitor front-end circuit includes: an access switch and a first controllable semiconductor device; wherein, The access switch is arranged in a transmission branch between the capacitor in the power converter and the corresponding power supply; The first controllable semiconductor device is connected in parallel with the access switch; The access switch is controlled to be turned off when the first controllable semiconductor device is in the on state.

2. The capacitor front-end circuit of the power converter according to claim 1, characterized in that: Also includes: Resistor branch; The resistance branch is connected in parallel with the first controllable semiconductor device.

3. The capacitor front-end circuit of the power converter according to claim 2, characterized in that: The resistance branch includes: one resistor, or at least two resistors connected in series and parallel.

4. The capacitor front-end circuit of the power converter according to claim 2, characterized in that: Also includes: a second controllable semiconductor device; The second controllable semiconductor device is connected in series with at least one resistor in the resistance branch to form a discharge circuit of the capacitor.

5. The capacitor front-end circuit of the power converter according to claim 4, characterized in that: The second controllable semiconductor device and the first controllable semiconductor device are integrated in the same module.

6. The capacitor front-end circuit of the power converter according to claim 2, characterized in that: Also includes: Anti-reverse device; One end of the anti-reverse device is connected to one end of the access switch close to the power supply; The other end of the anti-reverse device is connected to an end of the access switch close to the capacitor through a parallel branch formed by the first controllable semiconductor device and the resistance branch.

7. The capacitor front-end circuit of the power converter according to claim 6, characterized in that: The anti-reverse device is: a diode or a switch tube.

8. The capacitor front-end circuit of the power converter according to any one of claims 1 to 7, characterized in that: When the power source is a direct current power source, the access switch is arranged in a positive transmission branch between the capacitor and the corresponding power source.

9. The capacitor front-end circuit of the power converter according to claim 8, characterized in that: Also includes: Another access switch is arranged in the negative electrode transmission branch between the capacitor and the corresponding power source.

10. The capacitor front-end circuit of a power converter according to any one of claims 1 to 7, characterized in that: Also includes: A fuse device is arranged between the access switch and the corresponding power supply.

11. The capacitor front-end circuit of a power converter according to any one of claims 1 to 7, characterized in that: The access switch is: a circuit breaker, a relay or a contactor.

12. A power converter, characterized in that: include: A main circuit, at least one capacitor and a corresponding capacitor front-end circuit; wherein, The capacitor is provided on at least one side of the main circuit; The capacitor is connected to a corresponding power supply through the corresponding capacitor front-end circuit; The capacitor front-end circuit is a capacitor front-end circuit of a power converter as claimed in any one of claims 1 to 11.

13. The power converter according to claim 12, characterized in that: The main circuit is a bidirectional or unidirectional DC / DC conversion circuit or a DC / AC conversion circuit; Alternatively, the main circuit is a bidirectional or unidirectional AC / DC conversion circuit or an AC / AC conversion circuit.

14. A bidirectional charging pile, characterized in that: include: The power converter as claimed in claim 12; One side of the main circuit in the power converter is used to connect to the power battery of the electric vehicle.

15. The bidirectional charging pile according to claim 14, characterized in that: The main circuit includes at least one bidirectional DC / AC conversion circuit, the DC side of the bidirectional DC / AC conversion circuit is used to connect to the power battery, and the AC side of the bidirectional DC / AC conversion circuit is connected to the power grid.

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