CN114301271A

CN114301271A - Power conversion system and control method

Info

Publication number: CN114301271A
Application number: CN202110758478.0A
Authority: CN
Inventors: 胡彪; 刘洋; 陶腾; 徐勤勋
Original assignee: Huawei Digital Power Technologies Co Ltd
Current assignee: Huawei Digital Power Technologies Co Ltd
Priority date: 2021-07-05
Filing date: 2021-07-05
Publication date: 2022-04-08
Anticipated expiration: 2041-07-05
Also published as: CN114301271B

Abstract

A power conversion system and a control method are provided, which can reduce the volume and cost of a discharge resistor. The power conversion system includes: the DC/DC conversion module comprises a first DC/DC converter and a second DC/DC converter; the bleeder circuit comprises a discharge resistor R1 and a switching device Q4 which are connected in series; the controller is used for: when the power conversion system needs to discharge through the bleeder circuit, under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a series state, controlling the on-off of a switch in a switch switching circuit to switch the output ends of the first DC/DC converter and the second DC/DC converter from a series state to a parallel state; and after the output ends of the first DC/DC converter and the second DC/DC converter are switched into a parallel connection state, controlling the bleeder circuit to be in a conducting state.

Description

Power conversion system and control method

Technical Field

The present application relates to the electrical field, and more particularly, to a power conversion system and a control method.

Background

Many power conversion systems can output various dc voltages to be suitable for different application scenarios, i.e., the dc output voltage has a wide output range. A typical wide voltage output range power conversion system includes charging systems, such as passenger and bus charging stations. The charging voltage range of the passenger car is about 100V-500V, and the charging voltage range of the bus charging station is about 300V-700V.

According to the energy industry standard requirement, after the charging system stops supplying power, the output voltage should be reduced to below 60VDC (direct current voltage) within 1s (second). Therefore, in order to ensure that the discharging time of the charging system after the power supply is stopped reaches the industry standard requirement, a bleeder circuit needs to be added in the charging system to discharge the output capacitor. The bleeder circuit comprises a high-voltage resistant switching device and a discharge resistor. Since the discharge resistor and the switching device need to be selected according to the maximum output voltage, the volume and cost of the discharge resistor and the switching device are increased as the dc output range of the power conversion system is larger and larger.

Disclosure of Invention

The application provides a power conversion system and a control method, which can reduce the volume and the cost of a discharge resistor.

In a first aspect, a power conversion system is provided, including: the DC/DC conversion module is used for carrying out DC voltage conversion and outputting an output voltage V of the power conversion system_outSaid output voltage V_outThe DC/DC conversion module is used for supplying power to a load and comprises a first DC/DC converter and a second DC/DC converter; the controller is used for controlling the output ends of the first DC/DC converter and the second DC/DC converter to be in a series state or a parallel state by controlling the on-off of a switch in the switch switching circuit so as to change the output voltage V_out(ii) a The bleeder circuit is used for being arranged atAfter the power conversion system stops supplying power to the load, discharging charges at an output port of the power conversion system, wherein the discharging circuit is arranged between a positive output end and a negative output end of the power conversion system, and comprises a discharging resistor R1 and a switching device Q4 which are connected in series; the controller is further configured to: when the power conversion system needs to discharge through the bleeder circuit, under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a series state, controlling the on-off of a switch in the switch switching circuit to switch the output ends of the first DC/DC converter and the second DC/DC converter from a series state to a parallel state; and controlling the bleeding circuit to be in a conducting state.

By controlling the switch logic time sequence of the switch in the switch switching circuit and the switch device Q4 in the bleeder circuit in the power conversion system, the DC/DC conversion module discharges in the parallel mode, and the two ends of the discharge resistor R1 only need to bear the voltage of a single DC/DC converter when discharging, so that the maximum transient power borne by the discharge resistor R1 is reduced, and the space and the cost occupied by the bleeder circuit can be effectively saved in the selection of the discharge resistor R1.

With reference to the first aspect, in some implementations of the first aspect, the controller is further configured to: when the power conversion system needs to discharge through the bleeder circuit, the bleeder circuit is controlled to be in a conducting state under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a parallel connection state.

When the power conversion system needs to discharge through the bleeder circuit, if the output ends of the first DC/DC converter and the second DC/DC converter are determined to be in a parallel connection state, the state of the switch switching circuit does not need to be changed, and the two ends of the discharge resistor R1 can be ensured to only bear the voltage of a single DC/DC converter when the power conversion system discharges only by controlling the bleeder circuit 350 to be in a conduction state.

With reference to the first aspect, in some implementations of the first aspect, the switch switching circuit includes: a switch S1 disposed between the negative output terminal of the first DC/DC controller and the positive output terminal of the second DC/DC converter; a switch S2 disposed between the negative output terminal of the first DC/DC converter and the negative output terminal of the second DC/DC converter; a switch S3 provided between the positive output terminal of the first DC/DC converter and the positive output terminal of the second DC/DC converter; the controller is specifically configured to: controlling the switch S1 to be opened; after the switch S1 is turned off, controlling the switches S2 and S3 to be turned on so that the output terminals of the first DC/DC converter and the second DC/DC converter are switched into a parallel state; after the switches S2 and S3 are turned on, the switching device Q4 is controlled to be turned on so that the bleeding circuit is in a conductive state.

With reference to the first aspect, in some implementations of the first aspect, a transistor Q1 for clamping is further connected in parallel to two ends of the switch S1, and the controller is specifically configured to: after the switch S1 is turned off, controlling the transistor Q1 to be turned off; after the transistor Q1 is turned off, the switch S2 and the switch S3 are controlled to be turned on.

Clamping devices are connected in parallel across the switches S1, S2, and S3 so that when the switches S1, S2, and S3 are open, the voltage across the switches S1, S2, and S3 is maintained below a certain threshold by the clamping devices, thereby preventing an arc from occurring.

With reference to the first aspect, in some implementations of the first aspect, the power conversion system is a charging pile, and the load is an electric vehicle.

In a second aspect, a power conversion system is provided, comprising: the DC/DC conversion module is used for carrying out DC voltage conversion and outputting an output voltage V of the power conversion system_outSaid output voltage V_outThe DC/DC conversion module is used for supplying power to a load and comprises a first DC/DC converter and a second DC/DC converter; the controller is used for controlling the output ends of the first DC/DC converter and the second DC/DC converter to be in a series state or a parallel state by controlling the on-off of a switch in the switch switching circuit so as to change the output voltage V_out(ii) a The bleeder circuit is used for changing the power intoAfter the switching system stops supplying power to the load, discharging charge of an output port of the power conversion system, wherein the discharging circuit is arranged between a positive output end and a negative output end of the first DC/DC converter, or the discharging circuit is arranged between a positive output end and a negative output end of the second DC/DC converter, and the discharging circuit comprises a discharging resistor R1 and a switching device Q4 which are connected in series; the controller is further configured to: when the power conversion system needs to discharge through the bleeder circuit, under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a series state, controlling the on-off of a switch in the switch switching circuit to switch the output ends of the first DC/DC converter and the second DC/DC converter from a series state to a parallel state; and controlling the bleeding circuit to be in a conductive state after the output terminals of the first DC/DC converter and the second DC/DC converter are switched to a parallel state.

By controlling the switch logic sequence of the switch in the switch switching circuit in the power conversion system and the switch logic sequence of the switch device Q4 in the bleeder circuit, the DC/DC conversion module discharges in a parallel mode, and the two ends of the discharge resistor R1 only need to bear the voltage of a single DC/DC converter when discharging, so that the maximum transient power borne by the discharge resistor R1 is reduced, and the space and the cost occupied by the bleeder circuit can be effectively saved in the selection of the discharge resistor R1. In addition, because the bleeder circuit is arranged between the positive output end and the negative output end of the single DC/DC converter, the maximum voltage to be borne by the two ends of the switching device Q4 in the bleeder circuit is the output voltage of the single DC/DC converter, the switching device Q4 can be selected according to the specification of the output voltage of the single DC/DC converter, and the space and the cost occupied by the switching device Q4 are reduced.

With reference to the second aspect, in some implementations of the second aspect, the controller is further configured to: when the power conversion system needs to discharge through the bleeder circuit, the bleeder circuit is controlled to be in a conducting state under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a parallel connection state.

With reference to the second aspect, in some implementations of the second aspect, the switch switching circuit includes: a switch S1 disposed between the negative output terminal of the first DC/DC controller and the positive output terminal of the second DC/DC converter; a switch S2 disposed between the negative output terminal of the first DC/DC converter and the negative output terminal of the second DC/DC converter; a switch S3 provided between the positive output terminal of the first DC/DC converter and the positive output terminal of the second DC/DC converter; the controller is specifically configured to: controlling the switch S1 to be opened; after the switch S1 is turned off, controlling the switches S2 and S3 to be turned on so that the output terminals of the first DC/DC converter and the second DC/DC converter are switched into a parallel state; after the switches S2 and S3 are turned on, the switching device Q4 is controlled to be turned on so that the bleeding circuit is in a conductive state.

With reference to the second aspect, in some implementations of the second aspect, a transistor Q1 for clamping is further connected in parallel to two ends of the switch S1, and the controller is specifically configured to: after the switch S1 is turned off, controlling the transistor Q1 to be turned off; after the transistor Q1 is turned off, the switch S2 and the switch S3 are controlled to be turned on.

With reference to the second aspect, in some implementations of the second aspect, the power conversion system is a charging pile, and the load is an electric vehicle.

In a third aspect, a method for controlling a power conversion system is provided, the power conversion system including: controller, DC/DC/DC conversion module, switchA switching circuit and a bleeder circuit, wherein the DC/DC conversion module is used for performing DC voltage conversion and outputting an output voltage V of the power conversion system_outSaid output voltage V_outThe DC/DC conversion module is used for supplying power to a load and comprises a first DC/DC converter and a second DC/DC converter; the controller is used for controlling the output ends of the first DC/DC converter and the second DC/DC converter to be in a series state or a parallel state by controlling the on-off of a switch in the switch switching circuit so as to change the output voltage V_out(ii) a The bleeder circuit is used for discharging the charge of an output port of the power conversion system after the power conversion system stops supplying power to the load, the bleeder circuit is arranged between a positive output end and a negative output end of the power conversion system, and the bleeder circuit comprises a discharge resistor R1 and a switching device Q4 which are connected in series; the method comprises the following steps: when the power conversion system needs to be discharged through the bleeder circuit, the controller controls the on-off of a switch in the switch switching circuit under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a series state, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched from a series state to a parallel state; and the controller controls the bleeder circuit to be in a conductive state after the output terminals of the first DC/DC converter and the second DC/DC converter are switched to a parallel state.

With reference to the third aspect, in some implementations of the third aspect, the method further includes: the controller controls the bleeder circuit to be in a conducting state under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a parallel connection state when the power conversion system needs to be discharged through the bleeder circuit.

With reference to the third aspect, in some implementations of the third aspect, the switch switching circuit includes: a switch S1 disposed between the negative output terminal of the first DC/DC controller and the positive output terminal of the second DC/DC converter; a switch S2 disposed between the negative output terminal of the first DC/DC converter and the negative output terminal of the second DC/DC converter; a switch S3 provided between the positive output terminal of the first DC/DC converter and the positive output terminal of the second DC/DC converter; the controller controls on/off of a switch in the switch switching circuit so that the output terminals of the first DC/DC converter and the second DC/DC converter are switched from a series state to a parallel state when the output terminals of the first DC/DC converter and the second DC/DC converter are in a series state, including: the controller controls the switch S1 to open; the controller controls the switch S2 and the switch S3 to be turned on after the switch S1 is turned off, so that the output terminals of the first DC/DC converter and the second DC/DC converter are switched into a parallel state; the controller controls the bleeding circuit to be in a conducting state after the output terminals of the first DC/DC converter and the second DC/DC converter are switched to a parallel state, including: the controller controls the switching device Q4 to be turned on after the switches S2 and S3 are turned on, so that the bleeding circuit is in a conductive state.

With reference to the third aspect, in some implementations of the third aspect, a transistor Q1 for clamping is further connected in parallel to two ends of the switch S1, and the method further includes: the controller controls the transistor Q1 to turn off after the switch S1 turns off; the controller controls the switch S2 and the switch S3 to be turned on after the transistor Q1 is turned off.

With reference to the third aspect, in some implementations of the third aspect, the power conversion system is a charging pile, and the load is an electric vehicle.

In a fourth aspect, a method of controlling a power conversion system, the power conversion system, and the power conversion systemThe transformation system includes: the DC/DC conversion module is used for carrying out DC voltage conversion and outputting an output voltage V of the power conversion system_outSaid output voltage V_outThe DC/DC conversion module is used for supplying power to a load and comprises a first DC/DC converter and a second DC/DC converter; the controller is used for controlling the output ends of the first DC/DC converter and the second DC/DC converter to be in a series state or a parallel state by controlling the on-off of a switch in the switch switching circuit so as to change the output voltage V_out(ii) a The bleeder circuit is used for discharging the charge of an output port of the power conversion system after the power conversion system stops supplying power to the load, and is arranged between the positive output end and the negative output end of the first DC/DC converter or between the positive output end and the negative output end of the second DC/DC converter, and the bleeder circuit comprises a discharge resistor R1 and a switching device Q4 which are connected in series;

With reference to the fourth aspect, in some implementations of the fourth aspect, the method further includes: the controller controls the bleeder circuit to be in a conducting state under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a parallel connection state when the power conversion system needs to be discharged through the bleeder circuit.

With reference to the fourth aspect, in some implementations of the fourth aspect, the switch switching circuit includes: a switch S1 disposed between the negative output terminal of the first DC/DC controller and the positive output terminal of the second DC/DC converter; a switch S2 disposed between the negative output terminal of the first DC/DC converter and the negative output terminal of the second DC/DC converter; a switch S3 provided between the positive output terminal of the first DC/DC converter and the positive output terminal of the second DC/DC converter; the controller controls on/off of a switch in the switch switching circuit so that the output terminals of the first DC/DC converter and the second DC/DC converter are switched from a series state to a parallel state when the output terminals of the first DC/DC converter and the second DC/DC converter are in a series state, including: the controller controls the switch S1 to open; the controller controls the switch S2 and the switch S3 to be turned on after the switch S1 is turned off, so that the output terminals of the first DC/DC converter and the second DC/DC converter are switched into a parallel state; the controller controls the bleeding circuit to be in a conducting state after the output terminals of the first DC/DC converter and the second DC/DC converter are switched to a parallel state, including: the controller controls the switching device Q4 to be turned on after the switches S2 and S3 are turned on, so that the bleeding circuit is in a conductive state.

With reference to the fourth aspect, in some implementations of the fourth aspect, a transistor Q1 for clamping is further connected in parallel across the switch S1, and the method further includes: the controller controls the transistor Q1 to turn off after the switch S1 turns off; the controller controls the switch S2 and the switch S3 to be turned on after the transistor Q1 is turned off.

With reference to the fourth aspect, in some implementations of the fourth aspect, the power conversion system is a charging pile, and the load is an electric vehicle.

In a fifth aspect, a computer program product is provided, which comprises a computer program that, when executed, causes a computer to perform the method of any of the possible implementations of the third and fourth aspects and the third and fourth aspects described above.

A sixth aspect provides a computer-readable storage medium storing a computer program which, when run on a computer, causes the computer to perform the method of any one of the possible implementations of the third and fourth aspects and the third and fourth aspects described above.

Drawings

Fig. 1 is a schematic diagram of an application scenario according to an embodiment of the present application.

Fig. 2 is a schematic diagram of an application scenario of a further embodiment of the present application.

Fig. 3 is a schematic diagram of a power conversion system 200 according to an embodiment of the present application.

Fig. 4 is a current flow diagram of the power conversion system 200 of fig. 3 discharging in series mode.

Fig. 5 is a flowchart illustrating a control method 300 of a power conversion system according to an embodiment of the present application.

Fig. 6 is a current flow diagram of the power conversion system 200 of fig. 3 discharging in parallel mode.

Fig. 7 is a schematic structural diagram of a power conversion system 400 according to still another embodiment of the present application.

Fig. 8 is a schematic structural diagram of a power conversion system 400 according to still another embodiment of the present application.

Fig. 9 is a flowchart illustrating a control method 600 of a power conversion system according to an embodiment of the present application.

Fig. 10 is a current flow diagram of the power conversion system 400 of fig. 7 discharging in parallel mode.

Fig. 11 is a current flow diagram of the power conversion system 400 of fig. 8 discharging in parallel mode.

Detailed Description

The technical solution in the present application will be described below with reference to the accompanying drawings.

For ease of understanding, several terms referred to in the embodiments of the present application will be first introduced.

Metal-oxide-semiconductor field-effect transistor (MOSFET): the MOS transistor is a semiconductor device which works by applying a field effect principle, can be also called as an MOS transistor for short, and generally comprises three terminals, namely a grid electrode, a source electrode and a drain electrode.

Insulated Gate Bipolar Transistor (IGBT): the composite full-control voltage-driven power semiconductor device is a composite full-control voltage-driven power semiconductor device consisting of Bipolar Junction Transistors (BJTs) and MOSFETs, and has the advantages of both high input impedance of the MOSFETs and low conduction voltage drop of the BJTs.

Silicon Controlled Rectifier (SCR): the high-power switching type semiconductor device is a high-power switching type semiconductor device consisting of three PN junctions and can also be called a thyristor. The SCR has several types of one-way, two-way, turn-off and light control, has the advantages of small volume, light weight, convenient control and the like, and is widely applied to occasions of automatic control or high-power electric energy conversion such as rectification, voltage regulation, contactless switches and the like.

A relay: the electric control device is an electric appliance which generates a predetermined step change in a controlled amount in an electric output circuit when a change in an input amount meets a predetermined requirement. The system has an interactive relationship between a control system and a controlled system, and is generally applied to an automatic control circuit. The relay can be understood as an 'automatic switch' which uses small current to control large current operation, so that the relay plays roles of automatic adjustment, safety protection, circuit conversion and the like in a circuit, can be widely applied to remote control, remote measurement, communication, automatic control, electromechanical integration and power electronic equipment, and is one of the most important control elements.

Fig. 1 is a schematic diagram of an application scenario according to an embodiment of the present application. As shown in fig. 1, the power conversion system 100 is used for realizing the power conversion function and finally outputting a dc voltage V_outAnd supplying power to the load. For example, the power conversion system 100 may convert ac power into dc power, or may convert dc power into a voltage and output the voltage. The power conversion system 100 may have a wide dc output voltage range becauseThis output voltage can be adapted to different application scenarios. As an example, the power conversion system 100 may be a charging pile, a charging station, a mobile power replenishment train, or the like. The load can be an electric vehicle, an intelligent driving vehicle, a power battery, an energy storage battery, a capacitive load and the like. Alternatively, the power conversion system 100 may be a rectifier, a dc Uninterruptible Power Supply (UPS), or the like.

Fig. 2 is a schematic diagram of an application scenario of a further embodiment of the present application. As shown in fig. 2, the power conversion system 100 in fig. 1 may be the charging pile 21 in fig. 2, and the load may be the electric vehicle 24 in fig. 2. The input end of the charging pile 21 can be connected with alternating current, and the output end can output various direct current voltages so as to adapt to different types of electric vehicles 24. The alternating current received by the input end can be three-phase alternating current or single-phase alternating current. For example, if the load is a passenger car, the output dc voltage of the charging pile 21 is in a range of about 100V to 500V. If the load is a bus, the output dc voltage range of the charging pile 21 is about 300V to 700V. It can be seen that the dc output voltage of the charging pile 21 changes in a wide range, and with the technical progress, the charging pile 21 tends to develop to a higher charging voltage.

Fig. 3 is a schematic diagram of a power conversion system 200 according to an embodiment of the present application. The power conversion system 200 may be applied in the scenarios of fig. 1 or fig. 2. As shown in fig. 3, the power conversion system 200 may include a controller 310, a pre-stage module 320, a DC/DC conversion module 330, a switch switching circuit 340, and a bleeding circuit 350.

The controller 310 may be used to control, among other things, the switching of the switches in the various circuit modules in the power conversion system 200. Specifically, the controller 310 may be configured to send control signals to the respective switches to control the on/off of the respective switches. Optionally, the controller 310 may also be used to perform other management functions, such as detecting electrical parameters in the power conversion system 200, performing process calculation functions, and the like.

In some examples, power conversion system 200 is receiving input voltage V_inThereafter, power conversion may be performed by the pre-stage module 320, and a dc bus voltage V may be output_bus。DCthe/DC conversion module 330 receives the DC bus voltage V_busThen, the dc voltage conversion is performed, and the output voltage V of the power conversion system 200 is output_out。

In some examples, the input voltage V is_inThe power supply can be alternating current or direct current. The alternating current may be a three-phase alternating current or a single-phase alternating current.

In some examples, pre-stage module 320 may refer to circuitry located on a circuit link before DC/DC conversion module 330 in power conversion system 200. The embodiment of the present application does not limit the function of the front stage module 320 as long as it can input the voltage V_inProcessing and outputting a DC bus voltage V to DC/DC_busAnd (4) finishing. For example, pre-stage module 320 may be used for rectification, i.e., converting ac power to dc power. As an example, the pre-stage module 320 includes a Power Factor Correction (PFC) unit.

In order to realize various direct current output voltages, the DC/DC conversion module 330 may include two DC/DC converters, i.e., a first DC/DC converter 331 and a second DC/DC converter 332, and different direct current voltages may be output by changing series-parallel relationship of output terminals of the two DC/DC converters. For example, if the output voltage of a single DC/DC converter is V_dcWhen two DC/DC converters are connected in series, the voltage V output by the power conversion system 200_out＝2V_dc. Voltage V output by power conversion system 200 when two DC/DC converters are connected in parallel_out＝V_dc。

Alternatively, the two DC/DC converters can achieve an electrical isolation effect. By way of example, the two DC/DC converters may include, but are not limited to, an inductance inductance capacitance resonant circuit (LLC resonance circuit) or other type of bridge topology.

The switch switching circuit 340 includes a plurality of switches, and the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332 are in a series mode or a parallel mode by controlling on/off of the plurality of switches in the switch switching circuit 340.

As an example, the switch switching circuit 340 may include switches S1, S2, and S3. Wherein the switch S1 is disposed between the negative output terminal of the first DC/DC converter 331 and the positive output terminal of the second DC/DC converter 332. The switch S2 is disposed between the negative output terminal of the first DC/DC converter 331 and the negative output terminal of the second DC/DC converter 332. The switch S3 is disposed between the positive output terminal of the first DC/DC converter 331 and the positive output terminal of the second DC/DC converter 332. With the switch S1 on and the switches S2 and S3 off, the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332 are in series mode. With the switch S1 open and the switches S2 and S3 conductive, the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332 are in parallel mode.

In some examples, the switches S1, S2, and S3 may be relay, contactor, or the like type switches.

In some examples, due to the high voltage condition, if the switches S1, S2, and S3 are momentarily open, an arc will be generated in the air. To avoid this, a clamping device may be connected in parallel across the switches S1, S2, and S3, and when the switches S1, S2, and S3 are open, the voltage across the switches S1, S2, and S3 is maintained below a certain threshold by the clamping device, thereby preventing an arc from occurring. For example, in fig. 3, a transistor Q1 may be connected in parallel across the switch S1 as a clamping device. Diodes D2 and D3 may also be connected in parallel across switches S2 and S3, respectively, as clamping devices.

The above-mentioned clamping device may include, but is not limited to, at least one of: MOSFET, IGBT, SCR, diode. For example, the transistor Q1 may be any one of the following: MOSFET, IGBT, SCR.

It should be understood that there are other specific implementations of the switching circuit 340 as long as it can implement the series-parallel state conversion for controlling the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332.

The bleeding circuit 350 may be disposed at an output port of the power conversion system 200. For example, in fig. 3, the bleed circuit 350 is disposed between the positive and negative outputs of the power conversion system 200.

Optionally, an output capacitor C is further disposed at an output port of the power conversion system 200_out。

The bleeder circuit 350 includes a discharge resistor R1 and a switching device Q4 connected in series. The bleed circuit 350 may be used to bleed off charge at the output port of the power conversion system 200 after the power conversion system 200 stops supplying power. Or, the output capacitor C_outThe charge on both ends can be discharged through the bleeding circuit 350. Specifically, the controller 310 may control the switching device Q4 to be turned on and the output capacitor C to be turned on_outA discharge resistor R1 and a switch device Q4 form a discharge loop to output a capacitor C_outThe charge at both ends is discharged.

It should be appreciated that under normal operation of the power conversion system 200, the switching device Q4 is in an open state and the bleeding circuit 350 is not operational.

Alternatively, the switching device Q4 may include any one of the following devices: MOSFET, IGBT, SCR, and relay.

Fig. 4 is a current flow diagram of the power conversion system 200 of fig. 3 discharging in series mode. Wherein, when the output terminals of the first and second DC/

DC converters

331 and 332 are in the series mode, the output voltage V of the power conversion system 200_out＝2V_dcThe maximum voltage to be borne by the two ends of the bleeder circuit is 2V_dcThen the maximum transient power of the discharge resistor R1 is:

P_c＝(2V_dc)²/R1

wherein, P_cRepresenting the maximum transient power, V, of the discharge resistor R1_dcThe output voltages of the first DC/DC converter 331 and the second DC/DC converter 332 are shown.

In addition, as can be seen from fig. 4, the maximum voltage to be borne by the two ends of the switching device Q4 is 2V_dc。

Therefore, the discharge resistor R1 is required to be selected according to the maximum transient power P_c＝(2V_dc)²The type selection is carried out by the/R1, and the switching device Q4 needs to be based on 2V_dcThe specification of (2) is selected, the cost is high, and the occupied space is large.

In order to solve the above problem, embodiments of the present application provide a power conversion system (200, 400) and a corresponding control method (300, 600), which can reduce the voltage borne by the discharge resistor R1, and by reducing the voltage and power of the discharge resistor R1, the risk of device failure can be effectively reduced.

Fig. 5 is a flowchart illustrating a control method 300 of a power conversion system according to an embodiment of the present application. The control method 300 may be executed based on the power conversion system 200 in fig. 3. Specifically, the control method 300 may be performed by the controller 310 in the power conversion system 200. As shown in fig. 5, the control method 300 includes:

s301, when the power conversion system 200 needs to be discharged through the bleeding circuit 350, and the output ends of the first DC/DC converter 331 and the second DC/DC converter 332 are in a series state, the controller 310 controls on/off of the switch in the switch switching circuit 340, so that the output ends of the first DC/DC converter 331 and the second DC/DC converter 332 are switched from the series state to the parallel state.

For example, in series mode, switch S1 is on and transistor Q1 is on. When discharging is required, the controller 310 first turns off the switch S1, and after determining that S1 is reliably turned off, e.g., after a delay of 10-20 ms (milliseconds), turns off the transistor Q1. Switches S2 and S3 are then closed, such that DC/DC converter module 330 is in a parallel state, where V is_out＝V_dc。

S302, after the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332 are switched to the parallel connection state, the controller 310 controls the bleeding circuit 350 to be in the conduction state.

Specifically, the controller 310 may control the switching device Q4 in the bleeding circuit 350 to be turned on, so that the output capacitor C is turned on_outAnd bleed circuit 350 to form a path to output capacitance C_outDischarging through bleed circuit 350.

In addition, if the controller 310 determines that the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332 are in the parallel connection state when the power conversion system 200 needs to be discharged through the bleeding circuit 350, only the control needs to be performed without changing the state of the switch switching circuit 340The bleeder circuit 350 is in a conducting state, and the output voltage V is at the moment_out＝V_dc。

Fig. 6 is a current flow diagram of the power conversion system 200 of fig. 3 discharging in parallel mode. As shown in fig. 6, after the switching device Q4 is turned on, the maximum transient power of the discharge resistor R1 is:

P_c＝V_dc ²/R1

Therefore, the discharge resistor R1 is selected according to the maximum transient power P_c＝V_dc ²the/R1 is selected, the resistor power of the discharge resistor R1 is reduced by 3/4, and the space occupied by the bleeder circuit 350 and the cost can be effectively saved.

It should be noted that since the bleeding circuit 350 is disposed between the positive output terminal of the DC/DC converter 331 and the negative output terminal of the second DC/DC converter 332, the voltage across the bleeding circuit 350 is still 2V before the first DC/DC converter 331 and the second DC/DC converter 332 are switched to the parallel mode_dcTherefore, the maximum voltage to be borne across the switching device Q4 is still 2V_dcCan be according to 2V_dcThe specification selects the switching device Q4.

In the embodiment of the present application, by controlling the switching logic timing of the switch in the switch switching circuit 340 and the switching device Q4 in the bleeding circuit 350 in the power conversion system, the DC/DC conversion module 330 is discharged in the parallel mode, and both ends of the discharging resistor R1 only need to bear the voltage of a single DC/DC converter when discharging, so that the maximum transient power borne by the discharging resistor R1 is reduced, and the space and cost occupied by the bleeding circuit 350 can be effectively saved in the selection of the discharging resistor R1.

Fig. 7 and 8 are schematic structural diagrams of a power conversion system 400 according to still another embodiment of the present application. Among other things, power conversion system 400 differs from power conversion system 200 in that the bleed down circuit 350 in power conversion system 400 is connected in parallel at the output port of a single DC/DC converter. For example, the bleeder circuit 350 may be disposed between the positive and negative output terminals of the first DC/DC converter 331, or may be disposed between the positive and negative output terminals of the second DC/DC converter 332. In fig. 7, the bleeder circuit 350 is illustrated as being disposed between the positive output terminal and the negative output terminal of the second DC/DC converter 332. In fig. 8, the bleeder circuit 350 is provided between the positive output terminal and the negative output terminal of the first DC/DC converter 331 as an example.

It should be noted that the functions of the other modules in fig. 7 and fig. 8 are the same as those in fig. 3, and are not described again here.

Fig. 9 is a flowchart illustrating a control method 600 of a power conversion system according to an embodiment of the present application. The control method 600 is executed based on the power conversion system 400 in fig. 7 or fig. 8. Specifically, the control method 600 may be performed by the controller 310 in the power conversion system 400. As shown in fig. 9, the control method 600 includes:

s601, when the power conversion system 400 needs to discharge through the bleeder circuit 350, and the output ends of the first DC/DC converter 331 and the second DC/DC converter 332 are in a series state, the controller 310 controls on/off of the switch in the switch switching circuit 340, so that the output ends of the first DC/DC converter 331 and the second DC/DC converter 332 are switched from the series state to the parallel state.

For example, in series mode, the controller 310 controls the switch S1 to be turned on and the transistor Q1 to be turned on. When discharging is required, the controller 310 first turns off the switch S1, and after determining that S1 is reliably turned off, e.g., after a delay of 10-20 ms (milliseconds), turns off the transistor Q1. Switches S2 and S3 are then closed, at which time V_out＝V_dc。

S602, after the outputs of the first DC/DC converter 331 and the second DC/DC converter 332 are switched to the parallel connection state, the controller 310 controls the bleeding circuit 350 to be in the conduction state.

As a specific example, the controller may control the switching device Q4 in the bleeding circuit 350 to be turned on, so that the output capacitor C is turned on_outAnd bleed circuit 350 to form a path to output capacitance C_outDischarging through bleed circuit 350.

Fig. 10 is a current flow diagram of the power conversion system 400 of fig. 7 discharging in parallel mode. Fig. 11 is a current flow diagram of the power conversion system 400 of fig. 8 discharging in parallel mode. As shown in fig. 10 and 11, after the switching device Q4 is turned on, the maximum transient power of the discharge resistor R1 is:

P_c＝V_dc ²/R1

In addition, since the bleeder circuit 350 is disposed between the positive and negative output terminals of a single DC/DC converter (331, 332), the maximum transient voltage experienced across the bleeder circuit 350 is V_dcI.e. the maximum voltage to be sustained across the switching device Q4 is only the output voltage V of a single DC/DC converter_dcCan be according to V_dcThe specification selects the switching device Q4, and the space occupied by the switching device Q4 is reduced, and the cost is reduced.

In the embodiment of the present application, by controlling the switch logic timing of the switch in the switch switching circuit 340 and the switch logic timing of the switching device Q4 in the bleeding circuit 350 in the power conversion system, the DC/DC conversion module 330 discharges in the parallel mode, and the two ends of the discharge resistor R1 only need to bear the voltage of a single DC/DC converter when discharging, so that the maximum transient power borne by the discharge resistor R1 is reduced, and the space and the cost occupied by the bleeding circuit 350 can be effectively saved in the selection of the discharge resistor R1. In addition, since the bleeder circuit 350 is disposed between the positive output terminal and the negative output terminal of the single DC/DC converter, the maximum voltage to be borne by the two ends of the switching device Q4 in the bleeder circuit 350 is the output voltage of the single DC/DC converter, the switching device Q4 can be selected according to the specification of the output voltage of the single DC/DC converter, and the space and cost occupied by the switching device Q4 are reduced.

Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.

The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A power conversion system, comprising: a controller, a DC/DC/DC conversion module, a switch switching circuit and a bleeder circuit,

the DC/DC conversion module is used for performing DC voltage conversion and outputting an output voltage V of the power conversion system_outSaid output voltage V_outThe DC/DC conversion module is used for supplying power to a load and comprises a first DC/DC converter and a second DC/DC converter;

the controller is used for controlling the output ends of the first DC/DC converter and the second DC/DC converter to be in a series state or a parallel state by controlling the on-off of a switch in the switch switching circuit so as to change the output voltage V_out；

The bleeder circuit is used for discharging the charge of an output port of the power conversion system after the power conversion system stops supplying power to the load, the bleeder circuit is arranged between a positive output end and a negative output end of the power conversion system, and the bleeder circuit comprises a discharge resistor R1 and a switching device Q4 which are connected in series;

the controller is further configured to:

when the power conversion system needs to discharge through the bleeder circuit, under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a series state, controlling the on-off of a switch in the switch switching circuit to switch the output ends of the first DC/DC converter and the second DC/DC converter from a series state to a parallel state; and

and controlling the bleeder circuit to be in a conducting state.

2. The power conversion system of claim 1, wherein the controller is further to: when the power conversion system needs to discharge through the bleeder circuit, the bleeder circuit is controlled to be in a conducting state under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a parallel connection state.

3. The power conversion system according to claim 1 or 2, wherein the switch switching circuit includes:

a switch S1 disposed between the negative output terminal of the first DC/DC controller and the positive output terminal of the second DC/DC converter;

a switch S2 disposed between the negative output terminal of the first DC/DC converter and the negative output terminal of the second DC/DC converter;

a switch S3 provided between the positive output terminal of the first DC/DC converter and the positive output terminal of the second DC/DC converter;

the controller is specifically configured to:

controlling the switch S1 to be opened;

after the switch S1 is turned off, controlling the switches S2 and S3 to be turned on so that the output terminals of the first DC/DC converter and the second DC/DC converter are switched into a parallel state;

after the switches S2 and S3 are turned on, the switching device Q4 is controlled to be turned on so that the bleeding circuit is in a conductive state.

4. The power conversion system of claim 3, wherein a transistor Q1 for clamping is further connected in parallel across the switch S1,

the controller is specifically configured to:

after the switch S1 is turned off, controlling the transistor Q1 to be turned off;

after the transistor Q1 is turned off, the switch S2 and the switch S3 are controlled to be turned on.

5. The power conversion system according to any one of claims 1 to 4, wherein the power conversion system is a charging pile and the load is an electric vehicle.

6. A power conversion system, comprising: a controller, a DC/DC/DC conversion module, a switch switching circuit and a bleeder circuit,

The bleeder circuit is used for discharging the charge of an output port of the power conversion system after the power conversion system stops supplying power to the load, and is arranged between the positive output end and the negative output end of the first DC/DC converter or between the positive output end and the negative output end of the second DC/DC converter, and the bleeder circuit comprises a discharge resistor R1 and a switching device Q4 which are connected in series;

the controller is further configured to:

controlling the bleeding circuit to be in a conductive state after the output terminals of the first DC/DC converter and the second DC/DC converter are switched to a parallel state.

7. The power conversion system of claim 6, wherein the controller is further configured to: when the power conversion system needs to discharge through the bleeder circuit, the bleeder circuit is controlled to be in a conducting state under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a parallel connection state.

8. The power conversion system of claim 6 or 7, wherein the switch switching circuit comprises:

the controller is specifically configured to:

controlling the switch S1 to be opened;

9. The power conversion system of claim 8, wherein a transistor Q1 for clamping is further connected in parallel across the switch S1,

the controller is specifically configured to:

10. The power conversion system according to any one of claims 6 to 9, wherein the power conversion system is a charging pile and the load is an electric vehicle.

11. A method of controlling a power conversion system, the power conversion system comprising: a controller, a DC/DC/DC conversion module, a switch switching circuit and a bleeder circuit,

the method comprises the following steps:

when the power conversion system needs to be discharged through the bleeder circuit, the controller controls the on-off of a switch in the switch switching circuit under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a series state, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched from a series state to a parallel state; and

the controller controls the bleeding circuit to be in a conductive state after the output terminals of the first DC/DC converter and the second DC/DC converter are switched to a parallel state.

12. The method of claim 11, wherein the method further comprises:

the controller controls the bleeder circuit to be in a conducting state under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a parallel connection state when the power conversion system needs to be discharged through the bleeder circuit.

13. The method of claim 11 or 12, wherein the switch switching circuit comprises:

the controller controls on/off of a switch in the switch switching circuit so that the output terminals of the first DC/DC converter and the second DC/DC converter are switched from a series state to a parallel state when the output terminals of the first DC/DC converter and the second DC/DC converter are in a series state, including:

the controller controls the switch S1 to open;

the controller controls the switch S2 and the switch S3 to be turned on after the switch S1 is turned off, so that the output terminals of the first DC/DC converter and the second DC/DC converter are switched into a parallel state;

the controller controls the bleeding circuit to be in a conducting state after the output terminals of the first DC/DC converter and the second DC/DC converter are switched to a parallel state, including:

the controller controls the switching device Q4 to be turned on after the switches S2 and S3 are turned on, so that the bleeding circuit is in a conductive state.

14. The method of claim 13, wherein the switch S1 further has a transistor Q1 connected in parallel across it for clamping, the method further comprising:

the controller controls the transistor Q1 to turn off after the switch S1 turns off;

the controller controls the switch S2 and the switch S3 to be turned on after the transistor Q1 is turned off.

15. The method of any one of claims 11 to 14, wherein the power conversion system is a charging pile and the load is an electric vehicle.

16. A method of controlling a power conversion system, the power conversion system comprising: a controller, a DC/DC/DC conversion module, a switch switching circuit and a bleeder circuit,

the controller is used for controlling the switchSwitching on/off of a switch in a switching circuit to control output ends of the first DC/DC converter and the second DC/DC converter to be in a series state or a parallel state so as to change the output voltage V_out；

the method comprises the following steps:

17. The method of claim 16, wherein the method further comprises:

the controller controls the bleeder circuit to be in a conducting state under the condition that the output ends of the first DC/DC converter and the second DC/DC converter are in a parallel state when the power conversion system needs to be discharged through the bleeder circuit.

18. The method of claim 16 or 17, wherein the switch switching circuit comprises:

the controller controls the switch S1 to open;

19. The method of claim 18, wherein the switch S1 further has a transistor Q1 connected in parallel across it for clamping, the method further comprising:

20. The method of any one of claims 16 to 19, wherein the power conversion system is a charging pile and the load is an electric vehicle.