CN114301271B - Power conversion system and control method - Google Patents

Power conversion system and control method Download PDF

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Publication number
CN114301271B
CN114301271B CN202110758478.0A CN202110758478A CN114301271B CN 114301271 B CN114301271 B CN 114301271B CN 202110758478 A CN202110758478 A CN 202110758478A CN 114301271 B CN114301271 B CN 114301271B
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Prior art keywords
converter
switch
power conversion
conversion system
state
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CN202110758478.0A
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CN114301271A (en
Inventor
胡彪
刘洋
陶腾
徐勤勋
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Huawei Digital Power Technologies Co Ltd
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Huawei Digital Power Technologies Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/7072—Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/72—Electric energy management in electromobility
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02T90/10—Technologies relating to charging of electric vehicles
    • Y02T90/12—Electric charging stations

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  • Dc-Dc Converters (AREA)

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 discharging circuit comprises a discharging 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 connection state, the on-off of a switch in the switch switching circuit is controlled, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched from the series connection state to the parallel connection state; after the output ends of the first DC/DC converter and the second DC/DC converter are switched to be in a parallel state, the bleeder circuit is controlled to be in a conducting state.

Description

Power conversion system and control method
Technical Field
The present application relates to the electrical arts, and more particularly, to a power conversion system and 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 car charging stations and bus charging stations. Wherein, 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 standard requirements of the energy industry, 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 stopping power supply reaches the industry standard requirement, a bleeder circuit needs to be added in the charging system to discharge the output capacitor. The bleeder circuit includes a high voltage tolerant switching device and a discharge resistor. Since the discharge resistor and the switching device need to be selected according to the maximum output voltage, as the dc output range of the power conversion system is larger and larger, the volume and cost of the discharge resistor and the switching device are also increasing.
Disclosure of Invention
The application provides a power conversion system and a control method, which can reduce the volume and cost of a discharge resistor.
In a first aspect, a power conversion system is provided, comprising: the DC/DC conversion module is used for carrying out direct-current voltage conversion and outputting output voltage V of the power conversion system out The output voltage V out The DC/DC conversion module 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 serial 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 method comprises the steps of carrying out a first treatment on the surface of the The bleeder circuit is used for bleeding off the charge of the 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 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 be discharged through the bleeder circuit, controlling 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 connection state, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched from the series connection state to a parallel connection state; and controlling the bleeder circuit to be in a conductive state.
By controlling the switching 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 is discharged in the parallel mode, and the two ends of the discharging resistor R1 only need to bear the voltage of a single DC/DC converter during discharging, so that the maximum transient power born by the discharging resistor R1 is reduced, and the space and the cost occupied by the bleeder circuit can be effectively saved in the selection of the discharging 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 be discharged 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 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 is not required to be changed, and only the bleeder circuit 350 is required to be controlled to be in a conduction state, so that the two ends of the discharge resistor R1 can be ensured to bear the voltage of only a single DC/DC converter during discharge.
With reference to the first aspect, in some implementations of the first aspect, the switching circuit includes: the switch S1 is arranged between the negative output end of the first DC/DC controller and the positive output end of the second DC/DC converter; a switch S2 arranged between the negative output end of the first DC/DC converter and the negative output end of the second DC/DC converter; a switch S3 arranged between the positive output end of the first DC/DC converter and the positive output end of the second DC/DC converter; the controller is specifically used for: controlling the switch S1 to be opened; after the switch S1 is turned off, controlling the switch S2 and the switch S3 to be turned on so that the output ends of the first DC/DC converter and the second DC/DC converter are switched to a parallel state; after the switch S2 and the switch S3 are turned on, the switching device Q4 is controlled to be turned on so that the bleeder 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, the transistor Q1 is controlled 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 arcing.
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 direct-current voltage conversion and outputting output voltage V of the power conversion system out The output voltage V out The DC/DC conversion module 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 serial 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 method comprises the steps of carrying out a first treatment on the surface of the The bleeder circuit is used for bleeding off the charge of the 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 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 be discharged through the bleeder circuit, controlling 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 connection state, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched from the series connection state to a parallel connection state; at the saidAnd after the output ends of the first DC/DC converter and the second DC/DC converter are switched to be in a parallel state, the bleeder circuit is controlled to be in a conducting state.
By controlling the switch logic time sequence of the switch switching circuit in the power conversion system and the switch logic time sequence of the switch device Q4 in the bleeder circuit, the DC/DC conversion module is discharged in a parallel mode, and the two 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 born by the discharging resistor R1 is reduced, and the space and the cost occupied by the bleeder circuit can be effectively saved in the selection of the discharging resistor R1. In addition, since the bleeder circuit is arranged between the positive output end and the negative output end of the single DC/DC converter, the maximum voltage required to be born 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 occupied space and cost of 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 be discharged 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 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 is not required to be changed, and only the bleeder circuit 350 is required to be controlled to be in a conduction state, so that the two ends of the discharge resistor R1 can be ensured to bear the voltage of only a single DC/DC converter during discharge.
With reference to the second aspect, in some implementations of the second aspect, the switching circuit includes: the switch S1 is arranged between the negative output end of the first DC/DC controller and the positive output end of the second DC/DC converter; a switch S2 arranged between the negative output end of the first DC/DC converter and the negative output end of the second DC/DC converter; a switch S3 arranged between the positive output end of the first DC/DC converter and the positive output end of the second DC/DC converter; the controller is specifically used for: controlling the switch S1 to be opened; after the switch S1 is turned off, controlling the switch S2 and the switch S3 to be turned on so that the output ends of the first DC/DC converter and the second DC/DC converter are switched to a parallel state; after the switch S2 and the switch S3 are turned on, the switching device Q4 is controlled to be turned on so that the bleeder 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, the transistor Q1 is controlled 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 arcing.
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 control method of a power conversion system is provided, the power conversion system including: the DC/DC conversion module is used for carrying out direct-current voltage conversion and outputting output voltage V of the power conversion system out The output voltage V out The DC/DC conversion module 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 serial 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 method comprises the steps of carrying out a first treatment on the surface of the The bleeder circuit is used for bleeding off the charge of the output port of the power conversion system after the power conversion system stops supplying power to the load, and is arranged at the positive output end and the negative output end of the power conversion systemThe discharging circuit comprises a discharging resistor R1 and a switching device Q4 which are connected in series between the output ends; 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 connection state, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched from the series connection state to a parallel connection state; and the controller controls the bleeder circuit to be in a conducting state after the output ends of the first DC/DC converter and the second DC/DC converter are switched to be in a parallel state.
By controlling the switching 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 is discharged in the parallel mode, and the two ends of the discharging resistor R1 only need to bear the voltage of a single DC/DC converter during discharging, so that the maximum transient power born by the discharging resistor R1 is reduced, and the space and the cost occupied by the bleeder circuit can be effectively saved in the selection of the discharging resistor R1.
With reference to the third aspect, in some implementations of the third aspect, the method further includes: when the power conversion system needs to discharge through the bleeder circuit, 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.
With reference to the third aspect, in some implementations of the third aspect, the switch switching circuit includes: the switch S1 is arranged between the negative output end of the first DC/DC controller and the positive output end of the second DC/DC converter; a switch S2 arranged between the negative output end of the first DC/DC converter and the negative output end of the second DC/DC converter; a switch S3 arranged between the positive output end of the first DC/DC converter and the positive output end of the second DC/DC converter; the controller controls on-off of a switch in the switch switching circuit when 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 the series state to a parallel state, and the controller comprises: the controller controls the switch S1 to be opened; the controller controls the switch S2 and the switch S3 to be conducted after the switch S1 is disconnected, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched into a parallel state; the controller controls the bleeder circuit to be in a conducting state after the output ends of the first DC/DC converter and the second DC/DC converter are switched to be in a parallel state, and the controller comprises: the controller controls the switching device Q4 to be turned on after the switch S2 and the switch S3 are turned on, so that the bleeder 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 across the switch S1, and the method further includes: the controller controls the transistor Q1 to be turned off after the switch S1 is turned 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 control method of a power conversion system is provided, the power conversion system including: the DC/DC conversion module is used for carrying out direct-current voltage conversion and outputting output voltage V of the power conversion system out The output voltage V out The DC/DC conversion module 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 serial 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 method comprises the steps of carrying out a first treatment on the surface of the The bleeder circuit is used for bleeding off the charge of the output port of the power conversion system after the power conversion system stops supplying power to the load, the power conversion system comprises a power conversion circuitThe bleeder circuit 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 comprises a discharging resistor R1 and a switching device Q4 which are connected in series;
by controlling the switch logic time sequence of the switch switching circuit in the power conversion system and the switch logic time sequence of the switch device Q4 in the bleeder circuit, the DC/DC conversion module is discharged in a parallel mode, and the two 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 born by the discharging resistor R1 is reduced, and the space and the cost occupied by the bleeder circuit can be effectively saved in the selection of the discharging resistor R1. In addition, since the bleeder circuit is arranged between the positive output end and the negative output end of the single DC/DC converter, the maximum voltage required to be born 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 occupied space and cost of the switching device Q4 are reduced.
With reference to the fourth aspect, in some implementations of the fourth aspect, the method further includes: when the power conversion system needs to discharge through the bleeder circuit, 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.
With reference to the fourth aspect, in some implementations of the fourth aspect, the switching circuit includes: the switch S1 is arranged between the negative output end of the first DC/DC controller and the positive output end of the second DC/DC converter; a switch S2 arranged between the negative output end of the first DC/DC converter and the negative output end of the second DC/DC converter; a switch S3 arranged between the positive output end of the first DC/DC converter and the positive output end of the second DC/DC converter; the controller controls on-off of a switch in the switch switching circuit when 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 the series state to a parallel state, and the controller comprises: the controller controls the switch S1 to be opened; the controller controls the switch S2 and the switch S3 to be conducted after the switch S1 is disconnected, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched into a parallel state; the controller controls the bleeder circuit to be in a conducting state after the output ends of the first DC/DC converter and the second DC/DC converter are switched to be in a parallel state, and the controller comprises: the controller controls the switching device Q4 to be turned on after the switch S2 and the switch S3 are turned on, so that the bleeder 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 be turned off after the switch S1 is turned 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, there is provided a computer program product comprising a computer program which, when run, causes a computer to perform the method of the third and fourth aspects and any one of the possible implementations of the third and fourth aspects.
In a sixth aspect, there is provided a computer readable storage medium storing a computer program which, when run on a computer, causes the computer to perform the method of the third and fourth aspects and any one of the possible implementations of the third and fourth aspects.
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 according to another 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 flow chart of 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 diagram of a power conversion system 400 according to another embodiment of the present application.
Fig. 8 is a schematic diagram of a power conversion system 400 according to yet another embodiment of the present application.
Fig. 9 is a flow chart of 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 solutions 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 are first introduced.
Metal-oxide-semiconductor field-effect transistor (MOSFET): the semiconductor device is a semiconductor device which works by applying the field effect principle, can also be called an MOS tube for short, and generally comprises three terminals of a grid electrode, a source electrode and a drain electrode.
Insulated gate bipolar transistor (insulated gate bipolar transistor, IGBT): the power semiconductor device is a compound full-control voltage-driven power semiconductor device which consists of a bipolar transistor (bipolar junction transistor, BJT) and a MOSFET, and has the advantages of high input impedance of the MOSFET and low conduction voltage drop of the BJT.
Silicon controlled rectifiers (silicon controlled rectifier, SCR): is a high-power switch type semiconductor device composed of three PN junctions, and can also be called a thyristor. SCR has the advantages of unidirectional, bidirectional, turn-off, light control and the like, 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, a contactless switch and the like.
A relay: the electric control device is an electric appliance which causes a controlled quantity to generate a preset step change in an electric output circuit when the change of the input quantity reaches a prescribed requirement. It 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 regulation, safety protection, a switching circuit 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 configured to perform a power conversion function and finally output a dc voltage V out And 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 voltage and output the voltage. The power conversion system 100 may have a wide dc output voltage range, so the output voltage may be adapted to different application scenarios. As an example, the power conversion system 100 may be a charging stake, a charging station, a mobile electric make-up vehicle, or the like. The load may be an electric vehicle, an intelligent driving vehicle, a power battery, an energy storage battery, a capacitive load, etc. Alternatively, the power conversion system 100 may be a rectifier, a direct current uninterruptible power supply (uninterruptible power supply, UPS), or the like.
Fig. 2 is a schematic diagram of an application scenario according to another 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 the range of about 100V to 500V. If the load is a bus, the output dc voltage of the charging pile 21 is about 300V to 700V. It can be seen that the dc output voltage of the charging post 21 varies within a wide range, and as technology advances, the charging post 21 has a tendency to develop higher charging voltages.
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 scenario of fig. 1 or fig. 2. As shown in fig. 3, a controller 310, a pre-stage module 320, a DC/DC conversion module 330, a switching circuit 340, and a bleeder circuit 350 may be included in the power conversion system 200.
Among other things, the controller 310 may be used to control the switching of switches in 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. Alternatively, 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, the power conversion system 200 is receiving an input voltage V in Thereafter, the power conversion can be performed by the front stage module 320, and the DC bus voltage V is outputted bus . The DC/DC conversion module 330 receives the DC bus voltage V bus Then, the DC voltage conversion is performed to output the output voltage V of the power conversion system 200 out 。
In some examples, the input voltage V in Either alternating current or direct current. The alternating current may be three-phase alternating current or single-phase alternating current.
In some examples, the front stage module 320 may refer to circuitry located before the DC/DC conversion module 330 in the power conversion system 200 on a circuit link. The function of the front stage module 320 is not limited in the embodiment of the present application, as long as it can provide the input voltage V in Processing and outputting DC bus voltage V to DC/DC bus And (3) obtaining the product. For example, the pre-stage module 320 may be usedThe rectification, i.e. the conversion of alternating current into direct current. As an example, the above-described front stage module 320 includes a power factor correction (power factor correction, PFC) unit.
In order to realize various DC 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 DC voltages may be output by changing a serial-parallel relationship between the output ends of the two DC/DC converters. For example, if the output voltage of a single DC/DC converter is V dc Then, in the case where two DC/DC converters are connected in series, the voltage V output by the power conversion system 200 out ＝2V dc . In the case of two DC/DC converters in parallel, the voltage V output by the power conversion system 200 out ＝V dc 。
Alternatively, the two DC/DC converters can be electrically isolated. As an example, the two DC/DC converters may include, but are not limited to, an inductance-capacitance resonant circuit (inductance inductance capacitance resonant circuit, LLC resonant circuit) or other types of bridge topologies.
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 the on/off of the plurality of switches in the switch switching circuit 340.
As an example, switches S1, S2, and S3 may be included in the switch switching circuit 340. Wherein the switch S1 is arranged between the negative output of the first DC/DC converter 331 and the positive output of the second DC/DC converter 332. The switch S2 is provided between the negative output of the first DC/DC converter 331 and the negative output 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 switch S1 on and switches S2 and S3 off, the outputs of the first and second DC/DC converters 331 and 332 are in series mode. With switch S1 off and switches S2 and S3 on, the outputs of the first and second DC/DC converters 331 and 332 are in parallel mode.
In some examples, the switches S1, S2, and S3 may be relays, contactors, or the like.
In some examples, if switches S1, S2, and S3 are momentarily opened, an arc will be generated in the air because of the high voltage state. In order to avoid the above, clamping devices may be connected in parallel across the switches S1, S2 and S3, and when the switches S1, S2 and S3 are turned off, the clamping devices maintain the voltages across the switches S1, S2 and S3 below a certain threshold value, thereby preventing arcing. 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 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 appreciated that other implementations of the switching circuit 340 exist as long as it enables series-parallel state conversion of the outputs of the first DC/DC converter 331 and the second DC/DC converter 332.
A bleed circuit 350 may be provided at an output port of the power conversion system 200. For example, in fig. 3, a bleeder circuit 350 is provided between the positive and negative outputs of the power conversion system 200.
Optionally, an output capacitor C is further provided at the 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. After power conversion system 200 ceases to supply power, bleeder circuit 350 may be used to bleed off the charge from the output port of power conversion system 200. Or, output capacitance C out The charge across may be discharged through a bleeder circuit 350. Specifically, the controller 310 may control the switching device Q4 to be turned on and output the capacitance C out The discharging resistor R1 and the switching device Q4 form a discharging loop to output the capacitor C out The charge at both ends is released.
It should be appreciated that under normal operation of the power conversion system 200, the switching device Q4 is in an off state and the bleeder circuit 350 is not operating.
Alternatively, the switching device Q4 may include any one of the following devices: MOSFET, IGBT, SCR and a relay.
Fig. 4 is a current flow diagram of the power conversion system 200 of fig. 3 discharging in series mode. Wherein, in the case that the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332 are in a series mode, the output voltage V of the power conversion system 200 out ＝2V dc The maximum voltage to be born by the two ends of the bleeder circuit is 2V dc The maximum transient power of the discharge resistor R1 is:
P c ＝(2V dc ) 2 /R1
wherein P is c Representing the maximum transient power, V, of the discharge resistor R1 dc The 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 born by both ends of the switching device Q4 is 2V dc 。
Therefore, the maximum transient power P is required to be selected according to the discharge resistor R1 c ＝(2V dc ) 2 R1 is selected and the switching device Q4 is required to be selected according to 2V dc The specification of (3) is selected, the cost is high, and the occupied space is large.
In order to solve the above-mentioned problems, the embodiments of the present application provide a power conversion system (200, 400) and a corresponding control method (300, 600), which can reduce the voltage born by the discharge resistor R1, and can effectively reduce the risk of device failure by reducing the voltage and power of the discharge resistor R1.
Fig. 5 is a flow chart of a control method 300 of a power conversion system according to an embodiment of the present application. Wherein the control method 300 may be performed based on the power conversion system 200 of fig. 3. Specifically, the control method 300 may be performed by a 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 bleeder circuit 350, if the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332 are in a series state, the controller 310 controls the on/off of the switch in the switch switching circuit 340 so that the output terminals 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 turns off the transistor Q1 after determining that S1 is reliably turned off, for example, after a delay of 10 to 20ms (milliseconds). Then switches S2 and S3 are closed so that DC/DC conversion module 330 is in a parallel state, at which time V out ＝V dc 。
S302, the controller 310 controls the bleeder circuit 350 to be in a conductive state after the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332 are switched to a parallel state.
Specifically, the controller 310 may control the switching device Q4 in the bleeder circuit 350 to be turned on to cause the output capacitance C out Form a path with the bleeder circuit 350 to output a capacitance C out Discharged through the bleeder 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 state when the power conversion system 200 needs to be discharged through the bleeder circuit 350, the state of the switch switching circuit 340 is not required to be changed, and only the bleeder circuit 350 is required to be controlled to be in the on state, and the voltage V is outputted at this time 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
wherein P is c Representing the maximum transient power, V, of the discharge resistor R1 dc The output voltages of the first DC/DC converter 331 and the second DC/DC converter 332 are shown.
Therefore, the discharge resistor R1 can be selected according to the maximum transient power P c ＝V dc 2 R1 is selected, and the resistance of the discharge resistor R1 is equal to the resistanceThe rate is reduced by 3/4, which can effectively save the space and cost occupied by the bleeder circuit 350.
It should be noted that since the bleeder 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 bleeder circuit 350 is still 2V before the first and second DC/DC converters 331 and 332 are switched to the parallel mode dc Therefore, the maximum voltage to be borne across the switching device Q4 is still 2V dc Can be according to 2V dc Specification selection 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 bleeder circuit 350 in the power conversion system, the DC/DC conversion module 330 discharges in the parallel mode, and the two ends of the discharging resistor R1 only need to bear the voltage of a single DC/DC converter during discharging, so that the maximum transient power borne by the discharging resistor R1 is reduced, and the space and cost occupied by the bleeder 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 yet another embodiment of the present application. The power conversion system 400 differs from the power conversion system 200 in that the bleeder circuit 350 in the 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 provided between the positive and negative output terminals of the first DC/DC converter 331, or may be provided between the positive and negative output terminals of the second DC/DC converter 332. In fig. 7, the bleeder circuit 350 is exemplified as being provided 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 exemplified as being provided between the positive output terminal and the negative output terminal of the first DC/DC converter 331.
It should be noted that the functions of other modules in fig. 7 and 8 are the same as those in fig. 3, and are not repeated here.
Fig. 9 is a flow chart of a control method 600 of a power conversion system according to an embodiment of the present application. Wherein the control method 600 is performed based on the power conversion system 400 of fig. 7 or 8. In particular, 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 be discharged through the bleeder circuit 350, if the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332 are in a series state, the controller 310 controls the on/off of the switch in the switch switching circuit 340 so that the output terminals 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 the 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 turns off the transistor Q1 after determining that S1 is reliably turned off, for example, after a delay of 10 to 20ms (milliseconds). Switches S2 and S3 are then closed, at which time V out ＝V dc 。
S602, after the output terminals of the first DC/DC converter 331 and the second DC/DC converter 332 are switched to the parallel state, the controller 310 controls the bleeder circuit 350 to be in the conductive state.
As a specific example, the controller may control the switching device Q4 in the bleeder circuit 350 to turn on to cause the output capacitance C out Form a path with the bleeder circuit 350 to output a capacitance C out Discharged through the bleeder 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
wherein P is c Representing the maximum transient power, V, of the discharge resistor R1 dc The output voltages of the first DC/DC converter 331 and the second DC/DC converter 332 are shown.
Therefore, the discharge resistor R1 can be selected according to the maximum transient power P c ＝V dc 2 R1 is selected, the power of the discharging resistor R1 is reduced by 3/4, and the space occupied by the discharging circuit 350 and the power thereof can be effectively savedCost.
In addition, since the bleeder circuit 350 is disposed between the positive and negative output terminals of the single DC/DC converter (331, 332), the maximum transient voltage experienced across the bleeder circuit 350 is V dc I.e. the maximum voltage to be sustained across the switching device Q4 is the output voltage V of a single DC/DC converter dc Can be according to V dc The specification selects the switching device Q4, and reduces the space and cost occupied by 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 bleeder circuit 350 in the power conversion system, the DC/DC conversion module 330 discharges in the parallel mode, and the two ends of the discharging resistor R1 only need to bear the voltage of a single DC/DC converter during discharging, so that the maximum transient power borne by the discharging resistor R1 is reduced, and the space and cost occupied by the bleeder circuit 350 can be effectively saved in the selection of the discharging 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 born by the two ends of the switching device Q4 in the bleeder circuit 350 is the output voltage of the single DC/DC converter, and the switching device Q4 can be selected according to the specification of the output voltage of the single DC/DC converter, so that 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 solution. 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 will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the above-described systems, apparatuses and units may refer to corresponding procedures in the foregoing method embodiments, and are not repeated herein.
In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods may be implemented in other manners. For example, the apparatus embodiments described above are merely illustrative, e.g., the division of the units is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.
The units described as separate units may or may not be physically separate, and units shown 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 may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional unit in each embodiment of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in 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 may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
The foregoing is merely 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 think about changes or substitutions within the technical scope of the present application, and the changes and substitutions are intended to 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 (20)

1. A power conversion system, comprising: a controller, a direct current/direct current (DC/DC) conversion module, a switch switching circuit and a bleeder circuit,
the DC/DC conversion module is used for performing direct-current voltage conversion and outputting the output voltage V of the power conversion system out The output voltage V out The DC/DC conversion module 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 serial 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 bleeding off the charge of the 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 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 be discharged through the bleeder circuit, controlling 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 connection state, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched from the series connection state to a parallel connection 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 configured to: when the power conversion system needs to be discharged 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 state.
3. The power conversion system of claim 1 or 2, wherein the switch-switching circuit comprises:
the switch S1 is arranged between the negative output end of the first DC/DC controller and the positive output end of the second DC/DC converter;
a switch S2 arranged between the negative output end of the first DC/DC converter and the negative output end of the second DC/DC converter;
a switch S3 arranged between the positive output end of the first DC/DC converter and the positive output end of the second DC/DC converter;
the controller is specifically used for:
controlling the switch S1 to be opened;
after the switch S1 is turned off, controlling the switch S2 and the switch S3 to be turned on so that the output ends of the first DC/DC converter and the second DC/DC converter are switched to a parallel state;
after the switch S2 and the switch S3 are turned on, the switching device Q4 is controlled to be turned on so that the bleeder circuit is in a conductive state.
4. The power conversion system of claim 3, wherein a transistor Q1 for clamping is also connected in parallel across the switch S1,
the controller is specifically used for:
after the switch S1 is turned off, the transistor Q1 is controlled 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 direct current/direct current (DC/DC) conversion module, a switch switching circuit and a bleeder circuit,
the DC/DC conversion module is used for performing direct-current voltage conversion and outputting the output voltage V of the power conversion system out The output voltage V out The DC/DC conversion module 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 serial 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 bleeding off the charge of the 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 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 be discharged through the bleeder circuit, controlling 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 connection state, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched from the series connection state to a parallel connection state; and
and after the output ends of the first DC/DC converter and the second DC/DC converter are switched to be in a parallel state, controlling the bleeder circuit to be in a conducting state.
7. The power conversion system of claim 6, wherein the controller is further configured to: when the power conversion system needs to be discharged 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 state.
8. The power conversion system of claim 6 or 7, wherein the switch-switching circuit comprises:
the switch S1 is arranged between the negative output end of the first DC/DC controller and the positive output end of the second DC/DC converter;
a switch S2 arranged between the negative output end of the first DC/DC converter and the negative output end of the second DC/DC converter;
a switch S3 arranged between the positive output end of the first DC/DC converter and the positive output end of the second DC/DC converter;
the controller is specifically used for:
controlling the switch S1 to be opened;
after the switch S1 is turned off, controlling the switch S2 and the switch S3 to be turned on so that the output ends of the first DC/DC converter and the second DC/DC converter are switched to a parallel state;
after the switch S2 and the switch S3 are turned on, the switching device Q4 is controlled to be turned on so that the bleeder circuit is in a conductive state.
9. The power conversion system of claim 8, wherein a transistor Q1 for clamping is also connected in parallel across the switch S1,
the controller is specifically used for:
after the switch S1 is turned off, the transistor Q1 is controlled to be turned off;
After the transistor Q1 is turned off, the switch S2 and the switch S3 are controlled to be turned on.
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 direct current/direct current (DC/DC) conversion module, a switch switching circuit and a bleeder circuit,
the DC/DC conversion module is used for performing direct-current voltage conversion and outputting the output voltage V of the power conversion system out The output voltage V out The DC/DC conversion module 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 serial 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 bleeding off the charge of the 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 power conversion system and comprises a discharging 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 connection state, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched from the series connection state to a parallel connection state; and
the controller controls the bleeder circuit to be in a conducting state after the output ends of the first DC/DC converter and the second DC/DC converter are switched to be in a parallel state.
12. The method of claim 11, wherein the method further comprises:
when the power conversion system needs to discharge through the bleeder circuit, 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.
13. The method of claim 11 or 12, wherein the switch-switching circuit comprises:
the switch S1 is arranged between the negative output end of the first DC/DC controller and the positive output end of the second DC/DC converter;
A switch S2 arranged between the negative output end of the first DC/DC converter and the negative output end of the second DC/DC converter;
a switch S3 arranged between the positive output end of the first DC/DC converter and the positive output end of the second DC/DC converter;
the controller controls on-off of a switch in the switch switching circuit when 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 the series state to a parallel state, and the controller comprises:
the controller controls the switch S1 to be opened;
the controller controls the switch S2 and the switch S3 to be conducted after the switch S1 is disconnected, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched into a parallel state;
the controller controls the bleeder circuit to be in a conducting state after the output ends of the first DC/DC converter and the second DC/DC converter are switched to be in a parallel state, and the controller comprises:
the controller controls the switching device Q4 to be turned on after the switch S2 and the switch S3 are turned on, so that the bleeder circuit is in a conductive state.
14. The method of claim 13, wherein a transistor Q1 for clamping is also connected in parallel across the switch S1, the method further comprising:
the controller controls the transistor Q1 to be turned off after the switch S1 is turned 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 direct current/direct current (DC/DC) conversion module, a switch switching circuit and a bleeder circuit,
the DC/DC conversion module is used for performing direct-current voltage conversion and outputting the output voltage V of the power conversion system out The output voltage V out The DC/DC conversion module 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 serial 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 bleeding off the charge of the 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 comprises a discharging 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 connection state, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched from the series connection state to a parallel connection state; and
the controller controls the bleeder circuit to be in a conducting state after the output ends of the first DC/DC converter and the second DC/DC converter are switched to be in a parallel state.
17. The method of claim 16, wherein the method further comprises:
When the power conversion system needs to be discharged through the bleeder circuit, 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.
18. The method of claim 16 or 17, wherein the switch-switching circuit comprises:
the switch S1 is arranged between the negative output end of the first DC/DC controller and the positive output end of the second DC/DC converter;
a switch S2 arranged between the negative output end of the first DC/DC converter and the negative output end of the second DC/DC converter;
a switch S3 arranged between the positive output end of the first DC/DC converter and the positive output end of the second DC/DC converter;
the controller controls on-off of a switch in the switch switching circuit when 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 the series state to a parallel state, and the controller comprises:
the controller controls the switch S1 to be opened;
the controller controls the switch S2 and the switch S3 to be conducted after the switch S1 is disconnected, so that the output ends of the first DC/DC converter and the second DC/DC converter are switched into a parallel state;
The controller controls the bleeder circuit to be in a conducting state after the output ends of the first DC/DC converter and the second DC/DC converter are switched to be in a parallel state, and the controller comprises:
the controller controls the switching device Q4 to be turned on after the switch S2 and the switch S3 are turned on, so that the bleeder circuit is in a conductive state.
19. The method of claim 18, wherein a transistor Q1 for clamping is also connected in parallel across the switch S1, the method further comprising:
the controller controls the transistor Q1 to be turned off after the switch S1 is turned off;
the controller controls the switch S2 and the switch S3 to be turned on after the transistor Q1 is turned off.
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.
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