WO2024037058A1 - 飞跨电容三电平dcdc变换器、光伏系统及控制方法 - Google Patents

飞跨电容三电平dcdc变换器、光伏系统及控制方法 Download PDF

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Publication number
WO2024037058A1
WO2024037058A1 PCT/CN2023/092676 CN2023092676W WO2024037058A1 WO 2024037058 A1 WO2024037058 A1 WO 2024037058A1 CN 2023092676 W CN2023092676 W CN 2023092676W WO 2024037058 A1 WO2024037058 A1 WO 2024037058A1
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Prior art keywords
voltage
flying capacitor
diode
dcdc converter
bus
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PCT/CN2023/092676
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English (en)
French (fr)
Inventor
汪昌友
陈长春
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阳光电源股份有限公司
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Publication of WO2024037058A1 publication Critical patent/WO2024037058A1/zh

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Definitions

  • This application relates to the field of power electronics technology, and specifically to a flying capacitor three-level DCDC converter, a photovoltaic system and a control method.
  • the photovoltaic system In order to improve the power generation efficiency of the photovoltaic string, the photovoltaic system usually adds a first-level DCDC converter between the photovoltaic string and the inverter. It generally includes multiple DCDC converters, and the output ends of the multiple DCDC converters are connected in parallel to the inverter. input terminal. DCDC converters commonly used in high-voltage systems generally use three-level Boost circuits. Compared with the two-level Boost circuit, the voltage stress of the power device in the three-level Boost circuit is halved, the input current ripple is greatly reduced, and the size and cost of the inductor are reduced.
  • Figure 1 is a schematic diagram of a three-level DCDC converter with flying capacitors and clamping diodes.
  • the three-level Boost circuit with flying capacitor includes: inductor L, first switching tube Q1, second switching tube Q2, first diode D1, second diode D2, third diode D3 and flying capacitor.
  • the transcapacitor Cf in addition, it also includes the input capacitor Cin, and the input voltage is Vin.
  • the Boost circuit also includes two output capacitors Co1 and Co2 connected in series. The common point of Co1 and Co2 is the midpoint of the DC bus. The output voltage is the DC bus voltage Vbus.
  • a clamping diode D3 is also included.
  • the second end of the flying capacitor Cf is connected to the midpoint of the DC bus through the third diode D3.
  • the first terminal of the flying capacitor Cf is connected to the common terminal of D1 and D2.
  • Boost circuits Since the output terminals of multiple Boost circuits in the photovoltaic system are connected in parallel, some Boost circuits may have high input voltages and some may have low input voltages. When multiple Boost outputs are connected in parallel, the parallel output DC bus voltage will be the highest from the input voltage. All the way Boost is determined, which will cause the flying capacitor voltage of the Boost circuit with a lower input voltage to be charged to a voltage far less than the half bus, and even precharge cannot be achieved. At this time, if the boost circuit switch tube with a lower input voltage is started to work, its diode D2 will withstand excessive back pressure, leading to the risk of overvoltage failure.
  • this application provides a flying capacitor three-level DCDC converter, a photovoltaic system and a control method, which can protect the safety of each power device in the flying capacitor three-level DCDC converter.
  • This application provides a flying capacitor three-level DCDC converter, including: an inductor, a first switch tube, a second switch tube, a first diode, a second diode, a third diode, and a flying capacitor. and controller;
  • the first end of the inductor is connected to the positive input end of the DCDC converter, the second end of the inductor, the anode of the first diode, and the first end of the first switch tube are all connected to the first node;
  • the cathode of the first diode, the anode of the second diode, and the first end of the flying capacitor are all connected to the second node;
  • the second terminal of the first switching tube is connected to the negative input terminal of the DCDC converter through the second switching tube, the second terminal of the flying capacitor is connected to the midpoint of the DC bus through the third diode, and the cathode of the second diode is connected to the DCDC
  • the positive output terminal of the converter, the negative output terminal and the negative input terminal of the DCDC converter are connected together;
  • the controller is used for the difference between the DC bus voltage and the voltage of the flying capacitor to be greater than or equal to the withstand voltage of the second diode, to control the DCDC converter not to work, and to reduce the DC bus voltage.
  • the controller is specifically used to control the operation of the DCAC circuit to reduce the DC bus voltage, and the input end of the DCAC circuit is used to connect to the DC bus;
  • the controller is also used to control the operation of the DCDC converter when the difference between the DC bus voltage and the voltage of the flying capacitor is less than the withstand voltage of the second diode.
  • the controller is specifically used to control the duty cycle of the second switching tube to be greater than the duty cycle of the first switching tube when the voltage of the flying capacitor is less than the preset voltage value; the voltage of the flying capacitor is greater than the preset voltage value, The duty cycle of the second switching tube is controlled to be smaller than the duty cycle of the first switching tube.
  • the controller is also used to make the voltage of the flying capacitor equal to a preset voltage value, and to control the duty cycle of the second switching tube to be equal to the duty cycle of the first switching tube.
  • This application also provides a photovoltaic system, which includes at least two flying capacitor three-level DCDC converters introduced above; and also includes: a DCAC circuit;
  • the output terminals of at least two flying capacitor three-level DCDC converters are connected in parallel to the input terminal of the DCAC circuit;
  • each flying capacitor three-level DCDC converter is used to connect the corresponding photovoltaic string.
  • the DCDC converter includes: an inductor, a first switch tube, a second switch tube, a first diode, a second diode, a third Diodes and flying capacitors;
  • the method includes:
  • reducing the DC bus voltage specifically includes:
  • the method further includes: the difference between the DC bus voltage and the voltage of the flying capacitor is less than the withstand voltage of the second diode to control the operation of the DCDC converter.
  • controlling the operation of the DCDC converter specifically includes:
  • the voltage of the flying capacitor is less than the preset voltage value, and the duty cycle of the second switch tube is controlled to be greater than the duty cycle of the first switch tube;
  • the voltage of the flying capacitor is greater than the preset voltage value, and the duty cycle of the second switch tube is controlled to be smaller than the duty cycle of the first switch tube.
  • the method further includes: the voltage of the flying capacitor is equal to a preset voltage value, and the duty cycle of the second switch tube is controlled to be equal to the duty cycle of the first switch tube.
  • the flying capacitor three-level DCDC converter selects whether to turn on the flying capacitor three-level DCDC conversion by judging whether the difference between the DC bus voltage and the flying capacitor voltage is greater than the withstand voltage of the second diode.
  • the device is working.
  • the difference between the DC bus voltage and the voltage of the flying capacitor is greater than or equal to the withstand voltage of the second diode, it means that the DC bus voltage is too high or the flying capacitor precharge voltage is too low.
  • the DCDC conversion When the converter is working, the second diode will withstand too high a voltage, which can easily damage the second diode. Therefore, by reducing the DC bus voltage, the flying capacitor Cf will be charged up simultaneously until the DC bus voltage is equal to the flying capacitor. The voltage difference is less than the withstand voltage of the second diode. At this time, the DCDC converter is working, which can ensure the safety of the second diode.
  • Figure 1 is a schematic diagram of a three-level Boost circuit with flying capacitors
  • FIG. 2 is a schematic diagram of a photovoltaic system provided by this application.
  • Figure 3 is a schematic diagram of the second diode withstand voltage analysis provided by this application.
  • Figure 4 is a schematic diagram of a flying capacitor three-level DCDC converter provided by an embodiment of the present application.
  • Figure 5 is a schematic diagram of a photovoltaic system provided by an embodiment of the present application.
  • FIG. 6 is a flow chart of a control method for a flying capacitor three-level DCDC converter provided by an embodiment of the present application.
  • the embodiments of this application do not specifically limit the application scenarios of flying capacitor three-level DCDC converters, as long as the output terminals of multiple DCDC converters are connected in parallel. For example, it can be applied to the scenario of photovoltaic systems.
  • Each DCDC converter The input terminal is connected to the corresponding photovoltaic string.
  • the flying capacitor three-level DCDC converter will be referred to as DCDC converter for short in the following.
  • FIG. 2 is a schematic diagram of a photovoltaic system.
  • the photovoltaic system consists of two stages, one is a DCDC converter and the other is a DCAC circuit.
  • the DCDC converter including the Boost circuit is used as an example for introduction.
  • the input end of the first Boost circuit 101 is connected to the photovoltaic string PV1
  • the input end of the second Boost circuit 102 is connected to the photovoltaic string PV2
  • the output end of the first Boost circuit 101 and the output end of the second Boost circuit 102 are connected in parallel.
  • the output end of the DCAC circuit 103 can be connected to the power grid or an AC load.
  • the DCAC circuit 103 may be three-phase or single-phase.
  • the following introduction takes the Boost circuit as a three-level Boost circuit with flying capacitors as an example.
  • the three-level Boost circuit with flying capacitor includes: inductor L, first switching tube Q1, second switching tube Q2, first diode D1, second diode D2, third diode D3 and flying capacitor.
  • the first end of the inductor L is connected to the positive input end of the DCDC converter, the second end of the inductor L, the anode of the first diode D1, and the first end of the first switch Q1 are all connected to the first node;
  • the cathode of the first diode D1, the anode of the second diode D2, and the first end of the flying capacitor Cf are all connected to the second node;
  • the second terminal of the first switching tube Q1 is connected to the negative input terminal of the DCDC converter through the second switching tube Q2.
  • the second terminal of the flying capacitor Cf is connected to the midpoint of the DC bus through the third diode D3.
  • the second diode The cathode of D2 is connected to the positive output terminal of the DCDC converter, and the negative output terminal and negative input terminal of the DCDC converter are connected together.
  • D3 can realize the clamping function. It can simultaneously precharge the flying capacitor Cf and clamp the voltage stress of the switch tube when the input is powered on. It can precharge the voltage of the flying capacitor Cf to close to half of the bus voltage. Therefore, No additional precharge circuit is needed to ensure the voltage stress requirements of each power device when the Boost circuit is started.
  • the Boost circuit also includes an input capacitor Cin, which is connected in parallel between the positive input terminal and the negative input terminal of the Boost circuit, and the input voltage is Vin.
  • the Boost circuit also includes two output capacitors Co1 and Co2 connected in series.
  • the common point of Co1 and Co2 is the midpoint of the DC bus. In principle, the capacitance values of Co1 and Co2 are equal, and the voltage at the midpoint of the DC bus is half of the DC bus voltage Vbus.
  • the output voltage is the DC bus voltage Vbus.
  • the input voltage of each Boost circuit may be different, for example, the terrain of the power receiving station, solar radiation and external environmental factors (such as the installation inclination of the photovoltaic module, the module is blocked by dark clouds or vegetation, ice, snow/dust/sand cover, etc. ), the input voltage of each Boost circuit may be significantly different.
  • the DC bus voltage Vbus is determined by the Boost circuit with the highest input voltage.
  • the voltage of the flying capacitor of a Boost circuit with a lower input voltage can only be charged to a value much lower than that of the DC bus.
  • the voltage is half of Vbus, that is, far less than half the bus voltage, and even precharging cannot be achieved.
  • the voltage of the flying capacitor Cf is low, if the switching tube is started to work at this time (for example, Q2 is turned on), the diode D2 will have the risk of overvoltage (Vbus-Vcf) failure.
  • FIG. 3 is a schematic diagram of the second diode withstand voltage analysis provided by this application.
  • this application provides a flying capacitor three-level DCDC converter, which will be introduced in detail below with reference to the accompanying drawings.
  • FIG. 4 is a schematic diagram of a flying capacitor three-level DCDC converter provided by an embodiment of the present application.
  • connection relationship of each device in the flying capacitor three-level DCDC converter provided in this embodiment can be referred to the description in Figure 2 and will not be described again here.
  • the controller 400 controls the DCDC converter not to work and reduces the DC bus voltage Vbus when the difference between the DC bus voltage Vbus and the voltage of the flying capacitor Cf is greater than or equal to the withstand voltage of the second diode D2.
  • the embodiment of the present application does not specifically limit the withstand voltage of the second diode D2.
  • the second diode can be selected according to the DC bus voltage level of the flying capacitor three-level DCDC converter application scenario, such as the DC bus voltage level. It can be about 1500V, it can be a higher voltage level, or it can be a lower voltage level.
  • the flying capacitor Cf As the DC bus voltage decreases, the flying capacitor Cf is gradually charged, and the voltage of the flying capacitor Cf gradually increases.
  • the controller is specifically used to control the operation of the DCAC circuit to reduce the DC bus voltage Vbus.
  • the input end of the DCAC circuit is used to connect the DC bus; the DCAC circuit can be Control changes in electrical parameters to reduce the DC bus voltage Vbus.
  • the load may be a switching power supply device, a discharge circuit device, or the like.
  • the controller 400 is also used to control the operation of the DCDC converter when the difference between the voltage of the DC bus voltage Vbus and the flying capacitor Cf is less than the withstand voltage of the second diode D2, that is, when the DCDC converter is working, it will not cause the second diode D2 to operate.
  • the second diode D2 withstands an excessively high withstand voltage and will not cause damage to the second diode D2.
  • the controller 400 controls the operation of the DCDC converter mainly by sending driving signals to Q1 and Q2 to drive the switching states of Q1 and Q2.
  • the controller 400 controls the DCDC converter to stop sending driving signals, that is, blocking the wave, and Q1 and Q2 remain disconnected and do not move.
  • the three-level flying capacitor DCDC converter selects whether to turn on the three-level flying capacitor by judging whether the difference between the DC bus voltage and the voltage of the flying capacitor is greater than the withstand voltage of the second diode.
  • the DCDC converter is working.
  • the difference between the DC bus voltage and the voltage of the flying capacitor is greater than or equal to the withstand voltage of the second diode, it means that the DC bus voltage is too high or the flying capacitor precharge voltage is too low.
  • the second diode will withstand too high a voltage, which can easily damage the second diode. Therefore, by reducing the DC bus voltage, the flying capacitor Cf will be charged up simultaneously until the DC bus voltage is the same as the flying capacitor.
  • the difference in voltage across the capacitor is less than the withstand voltage of the second diode. At this time, the DCDC converter is working, which can ensure the safety of the second diode.
  • the flying capacitor three-level DCDC converter provided by the embodiment of the present application can directly start the DCDC converter even under the high-voltage DC bus and low-voltage input conditions of a certain DCDC converter, thus broadening the MPPT of the DCDC converter. working range, thereby increasing the system power generation.
  • this solution does not require additional costs and uses a software control solution to solve the voltage stress risk of the diode and the precharge problem of the floating capacitor voltage when the DC bus is high-voltage and the corresponding low-voltage input DCDC converter is started.
  • the controller controls the DCDC converter to work, which can include the following three situations:
  • the controller is specifically used to control the duty cycle of the second switching tube to be greater than the duty cycle of the first switching tube when the voltage of the flying capacitor is less than the preset voltage value; that is, in order to charge the flying capacitor, the flying capacitor is voltage across the capacitor.
  • the voltage of the flying capacitor is greater than the preset voltage value, and the duty cycle of the second switch tube is controlled to be smaller than the duty cycle of the first switch tube. That is, in order to discharge the flying capacitor, the voltage of the flying capacitor is reduced.
  • the controller is also used to control the voltage of the flying capacitor to be equal to the preset voltage value, and to control the duty cycle of the second switch tube to be equal to the duty cycle of the first switch tube.
  • the flying capacitor three-level DCDC converter provided by the embodiment of the present application can not only ensure the safety of the second diode, but also stabilize the voltage of the flying capacitor at a predetermined level on the premise that the second diode operates safely. Set the voltage value.
  • the flying capacitor three-level DCDC converter provided in the embodiment of the present application can also detect the input voltage of the flying capacitor three-level DCDC converter in real time, that is, the voltage of the photovoltaic string. Since the flying capacitor three-level DCDC converter When the input voltage of the converter is too low, even if the flying capacitor three-level DCDC converter does not work, the voltage of the flying capacitor cannot be increased by charging. Even if the DC bus voltage is reduced by using the method provided above in this application, it still cannot The difference between the DC bus voltage and the voltage of the flying capacitor is less than the withstand voltage of the second diode. Therefore, you can judge whether to enter the above control mode by judging the input voltage of the flying capacitor three-level DCDC converter, that is, control the DCDC converter to not work and reduce the DC bus voltage.
  • embodiments of the present application also provide a photovoltaic system, which will be described in detail below with reference to the accompanying drawings.
  • FIG. 5 is a schematic diagram of a photovoltaic system provided by an embodiment of the present application.
  • the photovoltaic system provided by the embodiment of the present application includes at least the flying capacitor three-level DCDC converter introduced above; the embodiment of the present application does not specifically limit the number of flying capacitor three-level DCDC converters in parallel.
  • Figure 5 Two flying capacitor three-level DCDC converters are used as an example for introduction. That is, the first flying capacitor three-level DCDC converter 101 and the second flying capacitor three-level DCDC converter 102. The input end of each flying capacitor three-level DCDC converter is used to connect the corresponding photovoltaic string. That is, the first flying capacitor three-level DCDC converter 101 is connected to PV1, and the input end of the second flying capacitor three-level DCDC converter 102 is connected to PV2.
  • the photovoltaic system also includes: DCAC circuit 103;
  • the output terminals of at least two flying capacitor three-level DCDC converters are connected in parallel to the input terminal of the DCAC circuit 103; that is, the output terminal of the first flying capacitor three-level DCDC converter 101 and the second flying capacitor three-level DCDC converter are connected in parallel.
  • the output terminals of the flat DCDC converter 102 are connected to the input terminals of the DCAC 103 circuit.
  • the input voltage Vin of the first flying capacitor three-level DCDC converter 101 is 800V
  • the input voltage of the second flying capacitor three-level DCDC converter 102 is 1400V.
  • the DC bus voltage Vbus will reach 1400V.
  • Q2 in the first flying capacitor three-level DCDC converter 101 is turned on, D2 in the first flying capacitor three-level DCDC converter 101 will have the risk of failure.
  • the controller controls the first flying capacitor three-level DCDC converter 101 and the second flying capacitor three-level DCDC converter 102 to not work at this time, and reduces the DC bus voltage Vbus, so that the DC bus voltage Only when the difference between the voltage of the flying capacitor and the flying capacitor is less than the withstand voltage of D2 is the first flying capacitor three-level DCDC converter 101 and the second flying capacitor three-level DCDC converter 102 controlled to operate.
  • the photovoltaic system provided by the embodiment of the present application can ensure the safety of the second diode in each flying capacitor three-level DCDC converter. Therefore, it can ensure the safety of each flying capacitor three-level DCDC converter, thereby ensuring the safety of each flying capacitor three-level DCDC converter. So that the photovoltaic system can work normally, thereby improving the power generation efficiency of the photovoltaic system.
  • embodiments of the present application also provide a control method for the flying capacitor three-level DCDC converter, which will be described in detail below with reference to the accompanying drawings.
  • FIG. 6 is a flow chart of a control method for a flying capacitor three-level DCDC converter provided by an embodiment of the present application.
  • the control method of the flying capacitor three-level DCDC converter provided in this embodiment is applied to the flying capacitor three-level DCDC converter introduced in the above embodiment, wherein the flying capacitor three-level DCDC converter includes: an inductor, A first switching tube, a second switching tube, a first diode, a second diode, a third diode and a flying capacitor;
  • the method includes:
  • S601 Determine that the difference between the DC bus voltage and the voltage of the flying capacitor is greater than or equal to the withstand voltage of the second diode, control the DCDC converter to not work, and reduce the DC bus voltage.
  • Reduce the DC bus voltage including:
  • the control method provided in this embodiment also includes: the difference between the DC bus voltage and the voltage of the flying capacitor is less than the withstand voltage of the second diode, and controlling the operation of the DCDC converter.
  • controlling the operation of the DCDC converter specifically includes:
  • the voltage of the flying capacitor is less than the preset voltage value, and the duty cycle of the second switch tube is controlled to be greater than the duty cycle of the first switch tube;
  • the voltage of the flying capacitor is greater than the preset voltage value, and the duty cycle of the second switch tube is controlled to be smaller than the duty cycle of the first switch tube.
  • the method also includes: the voltage of the flying capacitor is equal to a preset voltage value, and controlling the duty cycle of the second switch tube to be equal to the duty cycle of the first switch tube. This ensures that the charging and discharging of the flying capacitor remain balanced.
  • the control method of the flying capacitor three-level DCDC converter selects whether to turn on the flying capacitor by judging whether the difference between the DC bus voltage and the voltage of the flying capacitor is greater than the withstand voltage of the second diode.
  • the three-level DCDC converter is working.
  • the difference between the DC bus voltage and the voltage of the flying capacitor is greater than or equal to the withstand voltage of the second diode, it means that the DC bus voltage is too high or the floating capacitor precharge voltage is too low.
  • the DCDC converter is working, and the second diode will withstand too high a voltage, which can easily damage the second diode.
  • the flying capacitor Cf will be charged simultaneously until the DC bus voltage The difference between the voltage of the flying capacitor and the flying capacitor is less than the withstand voltage of the second diode. At this time, the DCDC converter is working, which can ensure the safety of the second diode.

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  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

本申请公开了一种飞跨电容三电平DCDC变换器、光伏系统及控制方法，飞跨电容三电平DCDC变换器包括：电感、第一开关管、第二开关管、第一二极管、第二二极管、第三二极管、飞跨电容和控制器；控制器，直流母线电压与飞跨电容的电压之差大于或等于第二二极管的耐受电压，控制DCDC变换器不工作，降低直流母线电压。当直流母线电压太高或者飞跨电容预充电压过低，此时DCDC变换器工作，第二二极管将承受太高的电压，容易使第二二极管损坏，因此，通过降低直流母线电压，飞跨电容Cf会同步被充电抬升，直至直流母线电压与飞跨电容的电压之差小于第二二极管的耐压，此时DCDC变换器进行工作，可以保证第二二极管的安全。

Description

飞跨电容三电平DCDC变换器、光伏系统及控制方法
本申请要求于2022年08月18日提交中国国家知识产权局的申请号为202210992839.2、申请名称为“飞跨电容三电平DCDC变换器、光伏系统及控制方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电力电子技术领域，具体涉及一种飞跨电容三电平DCDC变换器、光伏系统及控制方法。
背景技术
为了提高光伏组串的发电效能，光伏系统通常在光伏组串和逆变器之间加入一级DCDC变换器，一般包括多路DCDC变换器，多路DCDC变换器的输出端并联连接逆变器的输入端。高压系统常用的DCDC变换器一般采用三电平Boost电路。与两电平Boost电路相比，三电平Boost电路中功率器件的电压应力减半，输入电流纹波大幅减小，降低电感的体积和成本。
参见图1，该图为一种带有飞跨电容和钳位二极管的三电平DCDC变换器的示意图。
带有飞跨电容的三电平Boost电路包括：电感L、第一开关管Q1、第二开关管Q2、第一二极管D1、第二二极管D2、第三二极管D3和飞跨电容Cf；另外，还包括输入电容Cin，输入电压为Vin。Boost电路还包括串联的两个输出电容Co1和Co2，Co1和Co2的公共点为直流母线中点。输出电压为直流母线电压Vbus。为了同步实现对飞跨电容的预充电及保证Boost电路启动时各功率器件的电压应力要求，还包括钳位二极管D3。飞跨电容Cf的第二端通过第三二极管D3连接直流母线中点。飞跨电容Cf的第一端连接D1和D2的公共端。
由于光伏系统中多个Boost电路的输出端并联在一起，可能存在有的Boost电路的输入电压高，有的输入电压低，而多路Boost输出并联时，其并联输出直流母线电压由输入电压最高的一路Boost确定，这将导致输入电压较低的Boost电路的飞跨电容电压只能充电至远小于半母线的电压，甚至无法实现预充电。此时若启动输入电压较低的Boost电路开关管工作，其二极管D2将承受过高的反压，导致过压失效风险。
发明内容
为解决上述问题，本申请提供一种飞跨电容三电平DCDC变换器、光伏系统及控制方法，能够保护飞跨电容三电平DCDC变换器中各功率器件的安全。
本申请提供一种飞跨电容三电平DCDC变换器，包括：电感、第一开关管、第二开关管、第一二极管、第二二极管、第三二极管、飞跨电容和控制器；
电感的第一端连接DCDC变换器的正输入端，电感的第二端、第一二极管的阳极、第一开关管的第一端均连接第一节点；
第一二极管的阴极、第二二极管的阳极、飞跨电容的第一端均连接第二节点；
第一开关管的第二端通过第二开关管连接DCDC变换器的负输入端，飞跨电容的第二端通过第三二极管连接直流母线中点，第二二极管的阴极连接DCDC变换器的正输出端，DCDC变换器的负输出端和负输入端连接在一起；
控制器，用于直流母线电压与飞跨电容的电压之差大于或等于第二二极管的耐受电压，控制DCDC变换器不工作，降低直流母线电压。
优选地，控制器，具体用于控制DCAC电路工作来降低直流母线电压，DCAC电路的输入端用于连接直流母线；
或，
控制连接直流母线的负载工作来降低直流母线电压。
优选地，控制器，还用于直流母线电压与飞跨电容的电压之差小于第二二极管的耐受电压，控制DCDC变换器工作。
优选地，控制器，具体用于飞跨电容的电压小于预设电压值，控制第二开关管的占空比大于第一开关管的占空比；飞跨电容的电压大于预设电压值，控制第二开关管的占空比小于第一开关管的占空比。
优选地，控制器，还用于飞跨电容的电压等于预设电压值，控制第二开关管的占空比等于第一开关管的占空比。
本申请还提供一种光伏系统，包括至少两个以上介绍的飞跨电容三电平DCDC变换器；还包括：DCAC电路；
至少两个飞跨电容三电平DCDC变换器的输出端并联在一起连接DCAC电路的输入端；
每个飞跨电容三电平DCDC变换器的输入端用于连接对应的光伏组串。
本申请还提供一种飞跨电容三电平DCDC变换器的控制方法，DCDC变换器包括：电感、第一开关管、第二开关管、第一二极管、第二二极管、第三二极管和飞跨电容；
该方法包括：
获得直流母线电压和飞跨电容的电压；
判断直流母线电压与飞跨电容的电压之差大于或等于第二二极管的耐受电压，控制DCDC变换器不工作，降低直流母线电压。
优选地，降低直流母线电压，具体包括：
控制DCAC电路工作来降低直流母线电压，DCAC电路的输入端用于连接直流母线；
或，
控制连接直流母线的负载工作来降低直流母线电压
优选地，还包括：直流母线电压与飞跨电容的电压之差小于第二二极管的耐受电压，控制DCDC变换器工作。
优选地，控制DCDC变换器工作，具体包括：
飞跨电容的电压小于预设电压值，控制第二开关管的占空比大于第一开关管的占空比；
飞跨电容的电压大于预设电压值，控制第二开关管的占空比小于第一开关管的占空比。
优选地，还包括：飞跨电容的电压等于预设电压值，控制第二开关管的占空比等于第一开关管的占空比。
由此可见，本申请具有如下有益效果：
本申请提供的飞跨电容三电平DCDC变换器，通过判断直流母线电压与飞跨电容的电压之差是否大于第二二极管的耐压，来选择是否开启飞跨电容三电平DCDC变换器进行工作，当直流母线电压与飞跨电容的电压之差是否大于或等于第二二极管的耐压时，说明直流母线电压太高或者飞跨电容预充电压过低，此时DCDC变换器工作，第二二极管将承受太高的电压，容易使第二二极管损坏，因此，通过降低直流母线电压，飞跨电容Cf会同步被充电抬升，直至直流母线电压与飞跨电容的电压之差小于第二二极管的耐压，此时DCDC变换器进行工作，可以保证第二二极管的安全。
附图说明
图1为一种带有飞跨电容的三电平Boost电路的示意图；
图2为本申请提供的一种光伏系统的示意图；
图3为本申请提供的第二二极管承受电压分析示意图；
图4为本申请实施例提供的一种飞跨电容三电平DCDC变换器的示意图；
图5为本申请实施例提供的一种光伏系统的示意图；
图6为本申请实施例提供的一种飞跨电容三电平DCDC变换器的控制方法的流程图。
具体实施方式
为使本申请的上述目的、特征和优点能够更加明显易懂，下面结合附图和具体实施方式对本申请实施例作进一步详细的说明。
本申请实施例具体不限定飞跨电容三电平DCDC变换器的应用场景，只要多个DCDC变换器的输出端并联在一起即可，例如可以应用于光伏系统的场景，每个DCDC变换器的输入端连接对应的光伏组串。
为了方便描述，以下将飞跨电容三电平DCDC变换器简称为DCDC变换器。
下面以DCDC变换器应用于光伏系统为例进行介绍。
参见图2，该图为一种光伏系统的示意图。
光伏系统包括两级，一级为DCDC变换器，另一级为DCAC电路。其中以DCDC变换器包括Boost电路为例进行介绍。
为了便于描述，以两个Boost电路并联为例。
第一Boost电路101的输入端连接光伏组串PV1，第二Boost电路102的输入端连接光伏组串PV2，第一Boost电路101的输出端和第二Boost电路102的输出端并联在一起，均连接DCAC电路103的输入端。DCAC电路103的输出端可以连接电网，也可以连接交流负载。DCAC电路103可以为三相也可以为单相。
下面以Boost电路为带有飞跨电容的三电平Boost电路为例进行介绍。
继续参见图1。
带有飞跨电容的三电平Boost电路包括：电感L、第一开关管Q1、第二开关管Q2、第一二极管D1、第二二极管D2、第三二极管D3和飞跨电容Cf；
电感L的第一端连接DCDC变换器的正输入端，电感L的第二端、第一二极管D1的阳极、第一开关管Q1的第一端均连接第一节点；
第一二极管D1的阴极、第二二极管D2的阳极、飞跨电容Cf的第一端均连接第二节点；
第一开关管Q1的第二端通过第二开关管Q2连接DCDC变换器的负输入端，飞跨电容Cf的第二端通过第三二极管D3连接直流母线中点，第二二极管D2的阴极连接DCDC变换器的正输出端，DCDC变换器的负输出端和负输入端连接在一起。
D3可以实现钳位的作用，可在输入上电时同步实现对飞跨电容Cf的预充电及开关管电压应力的钳位，将飞跨电容Cf的电压预充电至接近母线电压的一半，因而无需额外的预充电电路，便可可保证Boost电路启动时各功率器件的电压应力要求。
另外，Boost电路还包括输入电容Cin，Cin并联在Boost电路的正输入端和负输入端之间，输入电压为Vin。Boost电路还包括串联的两个输出电容Co1和Co2，Co1和Co2的公共点为直流母线中点，原则上Co1和Co2的容值相等，直流母线中点的电压为直流母线电压Vbus的一半。输出电压为直流母线电压Vbus。
应该理解，由于多个Boost电路的输出端并联在一起连接直流母线，因此，直流母线电压Vbus会影响单个Boost电路的输出电压，稳态时，各个Boost电路的输出电压将与直流母线电压Vbus一致。
在光伏系统的应用场景，各个Boost电路的输入电压可能不同，例如，受电站现场地形、太阳辐照及外部环境因素(如光伏组件安装倾角、组件乌云或草木遮挡、冰雪/灰尘/风沙覆盖等)影响，每路Boost电路的输入电压可能存在较大差异。
由于多路Boost电路的输出端并联在一起，直流母线电压Vbus由输入电压最高的一路Boost电路决定，导致较低输入电压的某路Boost电路的飞跨电容的电压只能充电至远小于直流母线电压Vbus的一半，即远小于半母线电压，甚至无法实现预充电。进一步，由于飞跨电容Cf的电压较低，此时如果启动开关管工作(如Q2导通)，二极管D2将存在过压(Vbus-Vcf)失效的风险。下面结合附图进行详细分析。
参见图3，该图为本申请提供的第二二极管承受电压分析示意图。
以1500V光伏系统为例，其中包括两路Boost电路并联为例，假定一路Boost电路的输入电压Vin为800V，另一路Boost电路的输入电压为1400V，此时输出母线电压将达到1400V。
对于输入电压Vin为800V的Boost电路而言，由于半母线电压，即Co1和Co2上的电压相等，均为Vco2＝700V，输入电压Vin只能将飞跨电容Cf的电压预充电至100V，此时若直接启动开关管Q2导通工作，二极管D2将承受高压失效风险(VD2＝Vbus-Vcf＝1400V-100V＝1300V)，其中，Vcf表示飞跨电容Cf的电压。
本申请为了解决以上的技术问题，提供了一种飞跨电容三电平DCDC变换器，下面结合附图进行详细介绍。
参见图4，该图为本申请实施例提供的一种飞跨电容三电平DCDC变换器的示意图。
本实施例提供的飞跨电容三电平DCDC变换器中各个器件的连接关系可以参见图2的描述，在此不再赘述。
控制器400，用于直流母线电压Vbus与飞跨电容Cf的电压之差大于或等于第二二极管D2的耐受电压，控制DCDC变换器不工作，降低直流母线电压Vbus。
本申请实施例不具体限定第二二极管D2的耐受电压大小，可以根据飞跨电容三电平DCDC变换器应用场景的直流母线电压等级来选择第二二极管，例如直流母线电压等级可以为1500V左右，也可以为更高电压等级，也可以为更低电压等级。
直流母线电压在降低过程中，飞跨电容Cf逐渐被充电，飞跨电容Cf的电压逐渐升高。
本申请实施例不具体限定降低直流母线电压Vbus的具体方式，例如，控制器，具体用于控制DCAC电路工作来降低直流母线电压Vbus，DCAC电路的输入端用于连接直流母线；DCAC电路可以通过控制电参数的改变来降低直流母线电压Vbus。
或，
控制连接直流母线的负载工作来降低直流母线电压Vbus，即通过消耗能量来降低直流母线电压Vbus。
例如，负载可以为开关电源装置，也可以为放电电路装置等。
控制器400，还用于直流母线电压Vbus与飞跨电容Cf的电压之差小于第二二极管D2的耐受电压，控制DCDC变换器工作，即此时DCDC变换器工作，不会使第二二极管D2承受过高的耐压，不会使第二二极管D2损坏。
其中，控制器400控制DCDC变换器工作主要是向Q1和Q2发送驱动信号，驱动Q1和Q2的开关状态。控制器400控制DCDC变换器停止工作，是停止发送驱动信号，即封波，Q1和Q2保持断开状态，不动作。
本申请实施例提供的飞跨电容三电平DCDC变换器，通过判断直流母线电压与飞跨电容的电压之差是否大于第二二极管的耐压，来选择是否开启飞跨电容三电平DCDC变换器进行工作，当直流母线电压与飞跨电容的电压之差是否大于或等于第二二极管的耐压时，说明直流母线电压太高或飞跨电容预充电电压过低，此时DCDC变换器工作，第二二极管将承受太高的电压，容易使第二二极管损坏，因此，通过降低直流母线电压，飞跨电容Cf会同步被充电抬升，直至直流母线电压与飞跨电容的电压之差小于第二二极管的耐压，此时DCDC变换器进行工作，可以保证第二二极管的安全。
本申请实施例提供的飞跨电容三电平DCDC变换器，即使在直流母线高压及某路DCDC变换器低压输入条件下，本方案可以直接启动DCDC变换器，因此可拓宽了DCDC变换器的MPPT工作范围，进而提升系统发电量。同时本方案无需增加额外成本，采用软件控制方案，即可解决了直流母线高压时对应低压输入路DCDC变换器启机时二极管的电压应力风险及悬浮电容电压的预充电问题。
控制器控制DCDC变换器进行工作，具体可以包括以下三种情况：
第一：
控制器，具体用于飞跨电容的电压小于预设电压值，控制第二开关管的占空比大于所述第一开关管的占空比；即，为了给飞跨电容充电，升高飞跨电容的电压。
第二：
飞跨电容的电压大于预设电压值，控制第二开关管的占空比小于第一开关管的占空比。即，为了使飞跨电容放电，降低飞跨电容的电压。
第三：
控制器，还用于飞跨电容的电压等于预设电压值，控制第二开关管的占空比等于第一开关管的占空比。
本申请实施例提供的飞跨电容三电平DCDC变换器，不仅可以保证第二二极管的安全，还可以在第二二极管安全工作的前提下，使飞跨电容的电压稳定在预设电压值。
另外，本申请实施例提供的飞跨电容三电平DCDC变换器，还可以实时检测飞跨电容三电平DCDC变换器的输入电压，即光伏组串的电压，由于飞跨电容三电平DCDC变换器的输入电压太低时，即使飞跨电容三电平DCDC变换器不工作，飞跨电容的电压无法通过充电来升高，即使采用本申请以上提供的方式，降低直流母线电压，仍然不能满足直流母线电压与飞跨电容的电压之差小于第二二极管的耐压。因此，可以通过判断飞跨电容三电平DCDC变换器的输入电压来判断是否进入以上的控制方式，即控制DCDC变换器不工作，降低直流母线电压。
基于以上实施例提供的一种飞跨电容三电平DCDC变换器，本申请实施例还提供一种光伏系统，下面结合附图进行详细介绍。
参见图5，该图为本申请实施例提供的一种光伏系统的示意图。
本申请实施例提供的光伏系统，包括至少以上介绍的飞跨电容三电平DCDC变换器；本申请实施例具体不限定飞跨电容三电平DCDC变换器并联的数量，为了方便描述，图5中以两个飞跨电容三电平DCDC变换器为例进行介绍。即第一飞跨电容三电平DCDC变换器101和第二飞跨电容三电平DCDC变换器102。每个所述飞跨电容三电平DCDC变换器的输入端用于连接对应的光伏组串。即，第一飞跨电容三电平DCDC变换器101连接PV1，第二飞跨电容三电平DCDC变换器102的输入端连接PV2。
该光伏系统还包括：DCAC电路103；
至少两个飞跨电容三电平DCDC变换器的输出端并联在一起连接DCAC电路103的输入端；即第一飞跨电容三电平DCDC变换器101的输出端和第二飞跨电容三电平DCDC变换器102的输出端均连接DCAC103电路的输入端。
例如，第一飞跨电容三电平DCDC变换器101的输入电压Vin为800V，第二飞跨电容三电平DCDC变换器102的输入电压为1400V，此时直流母线电压Vbus将达到1400V。此时，如果第一飞跨电容三电平DCDC变换器101中的导通Q2，则第一飞跨电容三电平DCDC变换器101中的D2将有失效的风险。因此，为了保护D2，控制器此时控制第一飞跨电容三电平DCDC变换器101和第二飞跨电容三电平DCDC变换器102均不工作，降低直流母线电压Vbus，使直流母线电压与飞跨电容的电压之差小于D2的耐压，才控制第一飞跨电容三电平DCDC变换器101和第二飞跨电容三电平DCDC变换器102工作。
本申请实施例提供的光伏系统，可以保证每个飞跨电容三电平DCDC变换器中第二二极管的安全，因此，可以保证每个飞跨电容三电平DCDC变换器的安全，从而使光伏系统可以正常工作，进而提高光伏系统的发电效率。
基于以上实施例提供的一种飞跨电容三电平DCDC变换器及光伏系统，本申请实施例还提供一种飞跨电容三电平DCDC变换器的控制方法，下面结合附图进行详细介绍。
参见图6，该图为本申请实施例提供的一种飞跨电容三电平DCDC变换器的控制方法的流程图。
本实施例提供的飞跨电容三电平DCDC变换器的控制方法，应用于以上实施例介绍的飞跨电容三电平DCDC变换器，其中，飞跨电容三电平DCDC变换器包括：电感、第一开关管、第二开关管、第一二极管、第二二极管、第三二极管和飞跨电容；
该方法包括：
S601：获得直流母线电压和飞跨电容的电压；
S601：判断直流母线电压与飞跨电容的电压之差大于或等于第二二极管的耐受电压，控制DCDC变换器不工作，降低直流母线电压。
降低直流母线电压，具体包括：
控制DCAC电路工作来降低直流母线电压，DCAC电路的输入端用于连接直流母线；
或，
控制连接直流母线的负载工作来降低直流母线电压。
本实施例提供的控制方法，还包括：直流母线电压与飞跨电容的电压之差小于第二二极管的耐受电压，控制DCDC变换器工作。
其中，控制DCDC变换器工作，具体包括：
飞跨电容的电压小于预设电压值，控制第二开关管的占空比大于第一开关管的占空比；
飞跨电容的电压大于预设电压值，控制第二开关管的占空比小于第一开关管的占空比。
该方法，还包括：飞跨电容的电压等于预设电压值，控制第二开关管的占空比等于第一开关管的占空比。这样可以保证飞跨电容的充电和放电保持平衡。
本申请实施例提供的飞跨电容三电平DCDC变换器的控制方法，通过判断直流母线电压与飞跨电容的电压之差是否大于第二二极管的耐压，来选择是否开启飞跨电容三电平DCDC变换器进行工作，当直流母线电压与飞跨电容的电压之差是否大于或等于第二二极管的耐压时，说明直流母线电压太高或悬浮电容预充电电压过低，此时DCDC变换器工作，第二二极管将承受太高的电压，容易使第二二极管损坏，因此，通过降低直流母线电压，飞跨电容Cf会同步被充电抬升，直至直流母线电压与飞跨电容的电压之差小于第二二极管的耐压，此时DCDC变换器进行工作，可以保证第二二极管的安全。
对所公开的实施例的上述说明，使本领域专业技术人员能够实现或使用本申请。对这些实施例的多种修改对本领域的专业技术人员来说将是显而易见的，本文中所定义的一般原理可以在不脱离本申请的精神或范围的情况下，在其它实施例中实现。因此，本申请将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。

Claims (11)

  1. 一种飞跨电容三电平DCDC变换器，其特征在于，包括：电感、第一开关管、第二开关管、第一二极管、第二二极管、第三二极管、飞跨电容和控制器；
    所述电感的第一端连接所述DCDC变换器的正输入端，所述电感的第二端、所述第一二极管的阳极、所述第一开关管的第一端均连接第一节点；
    所述第一二极管的阴极、所述第二二极管的阳极、所述飞跨电容的第一端均连接第二节点；
    所述第一开关管的第二端通过所述第二开关管连接所述DCDC变换器的负输入端，所述飞跨电容的第二端通过所述第三二极管连接直流母线中点，所述第二二极管的阴极连接所述DCDC变换器的正输出端，所述DCDC变换器的负输出端和负输入端连接在一起；
    所述控制器，用于直流母线电压与所述飞跨电容的电压之差大于或等于所述第二二极管的耐受电压，控制所述DCDC变换器不工作，降低所述直流母线电压。
  2. 根据权利要求1所述的DCDC变换器，其特征在于，所述控制器，具体用于控制DCAC电路工作来降低所述直流母线电压，所述DCAC电路的输入端用于连接所述直流母线；
    或，
    控制连接所述直流母线的负载工作来降低所述直流母线电压。
  3. 根据权利要求1或2所述的DCDC变换器，其特征在于，所述控制器，还用于所述直流母线电压与所述飞跨电容的电压之差小于所述第二二极管的耐受电压，控制所述DCDC变换器工作。
  4. 根据权利要求3所述的DCDC变换器，其特征在于，所述控制器，具体用于所述飞跨电容的电压小于预设电压值，控制所述第二开关管的占空比大于所述第一开关管的占空比；所述飞跨电容的电压大于所述预设电压值，控制所述第二开关管的占空比小于所述第一开关管的占空比。
  5. 根据权利要求4所述的DCDC变换器，其特征在于，所述控制器，还用于所述飞跨电容的电压等于预设电压值，控制所述第二开关管的占空比等于所述第一开关管的占空比。
  6. 一种光伏系统，其特征在于，包括至少两个权利要求1-5任一项所述的飞跨电容三电平DCDC变换器；还包括：DCAC电路；
    至少两个所述飞跨电容三电平DCDC变换器的输出端并联在一起连接所述DCAC电路的输入端；
    每个所述飞跨电容三电平DCDC变换器的输入端用于连接对应的光伏组串。
  7. 一种飞跨电容三电平DCDC变换器的控制方法，其特征在于，所述DCDC变换器包括：电感、第一开关管、第二开关管、第一二极管、第二二极管、第三二极管和飞跨电容；
    该方法包括：
    获得直流母线电压和所述飞跨电容的电压；
    判断所述直流母线电压与所述飞跨电容的电压之差大于或等于所述第二二极管的耐受电压，控制所述DCDC变换器不工作，降低所述直流母线电压。
  8. [根据细则26改正 13.07.2023]
    根据权利要求7所述的控制方法，其特征在于，所述降低所述直流母线电压，具体包括：
    控制DCAC电路工作来降低所述直流母线电压，所述DCAC电路的输入端用于连接所述直流母线；
    或，
    控制连接所述直流母线的负载工作来降低所述直流母线电压。
  9. 根据权利要求7或8所述的控制方法，其特征在于，还包括：所述直流母线电压与所述飞跨电容的电压之差小于所述第二二极管的耐受电压，控制所述DCDC变换器工作。
  10. 根据权利要求9所述的控制方法，其特征在于，所述控制所述DCDC变换器工作，具体包括：
    所述飞跨电容的电压小于预设电压值，控制所述第二开关管的占空比大于所述第一开关管的占空比；
    所述飞跨电容的电压大于所述预设电压值，控制所述第二开关管的占空比小于所述第一开关管的占空比。
  11. 根据权利要求10所述的控制方法，其特征在于，还包括：所述飞跨电容的电压等于预设电压值，控制所述第二开关管的占空比等于所述第一开关管的占空比。
PCT/CN2023/092676 2022-08-18 2023-05-08 飞跨电容三电平dcdc变换器、光伏系统及控制方法 WO2024037058A1 (zh)

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