WO2023246512A1 - 多电平直流变换器和飞跨电容的电压控制方法、控制装置 - Google Patents

多电平直流变换器和飞跨电容的电压控制方法、控制装置 Download PDF

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Publication number
WO2023246512A1
WO2023246512A1 PCT/CN2023/098923 CN2023098923W WO2023246512A1 WO 2023246512 A1 WO2023246512 A1 WO 2023246512A1 CN 2023098923 W CN2023098923 W CN 2023098923W WO 2023246512 A1 WO2023246512 A1 WO 2023246512A1
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WIPO (PCT)
Prior art keywords
switching tube
voltage
duty cycle
flying capacitor
switch
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PCT/CN2023/098923
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English (en)
French (fr)
Inventor
武荣
钟少辉
吴志清
赵兢
樊军涛
Original Assignee
华为数字能源技术有限公司
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Publication of WO2023246512A1 publication Critical patent/WO2023246512A1/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
    • H02M3/1584—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 with a plurality of power processing stages connected in parallel

Definitions

  • the present application relates to the field of power electronics technology, and in particular to a voltage control method and control device for a multi-level DC converter and a flying capacitor.
  • the multi-level DC converter can reduce the voltage stress of the input voltage on each switching tube by adding flying capacitance.
  • flying capacitance Taking a three-level DC converter with a flying capacitor as an example, half of the input voltage can be stored through the flying voltage, so that the output levels have three types: 0, 1/2 and 1, and their change amplitude is that of a two-level topology.
  • Half, and then low-voltage switching tubes can be used to improve the performance of electronic systems.
  • the charging and discharging time of the flying capacitor can be adjusted by judging the current direction of the inductor and adjusting the duty cycle difference between the first switching tube (or the second switching tube) in the switching tube group to achieve the purpose.
  • the voltage across the flying capacitor is controlled.
  • controlling the voltage of the flying capacitor according to the instantaneous current direction places extremely high requirements on the control chip and cannot be applied to actual applications. Under construction.
  • Embodiments of the present application disclose a voltage control method and control device for a multi-level DC converter and a flying capacitor, which can control the voltage of the flying capacitor and improve the operation stability of the multi-level DC converter.
  • inventions of the present application disclose a multi-level DC converter.
  • the multi-level DC converter includes at least one flying capacitor, two switching tube groups connected to the flying capacitor, and each switching tube group.
  • An inductor connected to the positive terminal of the low-voltage power supply of the multi-level DC converter, and a controller for controlling the switch tube group; wherein the switch tube group includes a first switch tube and a second switch tube in complementary on- and off-states.
  • the first switch tube is connected to one end of the high-voltage power supply of the multi-level DC converter
  • the second switch tube is connected to the other end of the high-voltage power supply of the multi-level DC converter
  • the controller is used to sample the voltage and reference of the flying capacitor
  • the duty cycle difference between the first switch tube in the two switch tube groups or the duty cycle difference between the first switch tube in the two switch tube groups is adjusted according to the size of the inductor current.
  • the phase difference between the carrier waves of the first switching tube is adjusted according to the size of the inductor current.
  • a multi-level DC converter or may be called a multi-level DC converter, is used to perform direct current (DC)-to-DC power conversion. For example, it can be a step-up conversion or a step-down conversion.
  • This application is for multi-level DC transformers
  • the specific type of converter is not limited and can be a three-level DC converter, a five-level DC converter, a seven-level DC converter, etc.
  • the multi-level topology corresponding to the multi-level DC converter means that the output level has at least three states. For example, if the output level has three states: 1, 1/2 and 0, it is called a three-level topology.
  • the output level has The five states of 1, 3/4, 1/2, 1/4 and 0 are called five-level topology.
  • the first switch tube and the second switch tube may be field-effect transistor (FET), metal-oxide-semiconductor field-effect transistor (MOSFET), or insulated gate bipolar transistor. (insulated gate bipolar transistor, IGBT), junction field-effect transistor (JFET), and their parallel diodes are not limited here.
  • FET field-effect transistor
  • MOSFET metal-oxide-semiconductor field-effect transistor
  • insulated gate bipolar transistor IGBT
  • JFET junction field-effect transistor
  • the controller can be a pulse width modulation (PWM) device, or a battery management system (BMS) based on PWM technology, a micro control unit (MCU), or a central processing unit (central processing unit). , CPU), other general-purpose processors, digital signal processors (digital signal processors, DSPs), application specific integrated circuits (ASICs), off-the-shelf programmable gate arrays (field-programmable gate arrays, FPGAs) or other available Programmed logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.
  • the controller can be one chip or multiple chips with communication connections.
  • the controller may include a control unit corresponding to each switch tube, or may include a control unit corresponding to the switch tube group, for example, a pulse width modulator corresponding to the first switch tube and the second switch tube in the switch tube group, where No restrictions.
  • the sampling voltage of the flying capacitor is the collected real-time voltage.
  • the reference voltage of the flying capacitor is the target value to be adjusted for the flying capacitor.
  • the current of the inductor also known as the inductor current, can be the instantaneous current value or the average value.
  • This application does not limit the first threshold, and it can be 0 and so on. It can be understood that if the absolute value of the difference between the sampling voltage of the flying capacitor and the reference voltage is greater than the first threshold, it means that the voltage of the flying capacitor has not been adjusted to the target value (for example, the target value of the three-level DC converter The value can be 1/2 times the voltage of the high-voltage power supply), and you can continue to adjust the duty cycle difference between the switching tubes on one side of the flying capacitor, or the phase difference between the carriers of the first switching tube on that side, thereby adjusting the Controlling the voltage of the flying capacitor can reduce the voltage stress of the multi-level DC converter.
  • the target value for example, the target value of the three-level DC converter
  • the value can be 1/2 times the voltage of the high-voltage power supply
  • the difference between the sampling voltage of the flying capacitor and the reference voltage is less than or equal to the first threshold, it means that the voltage of the flying capacitor has been adjusted to the target value, and the current working state can be maintained to continue working. In this way, the operation stability of the multi-level DC converter can be improved.
  • the controller is specifically configured to determine and adjust the phase difference between the first switching tube carriers in the two switching tube groups according to the magnitude of the inductor current, and the flying capacitor When the sampled voltage is less than the reference voltage, the phase difference between the carrier waves of the first switch tube in the two switch tube groups is increased. In this way, the voltage of the flying capacitor can be increased.
  • the controller is specifically configured to determine and adjust the phase difference between the first switching tube carriers in the two switching tube groups according to the magnitude of the inductor current, and the flying capacitor.
  • the sampling voltage is greater than the reference voltage
  • the phase difference between the carrier waves of the first switch tube in the two switch tube groups is reduced. In this way, the voltage across the flying capacitor can be reduced.
  • the controller is specifically configured to adjust the inductor current when the inductor current is less than the second threshold.
  • the controller is specifically configured to adjust the duty cycle difference between the first switching tubes in the two switching tube groups when the inductor current is greater than the third threshold.
  • the controller is specifically configured to operate when the inductor current is greater than or equal to the second threshold, and less than or equal to the third threshold, adjust the duty cycle difference between the first switching tubes in the two switching tube groups or the carrier wave between the first switching tubes in the two switching tube groups according to the adjustment method at the previous moment. phase difference.
  • This application does not limit the size of the second threshold and the third threshold, and the second threshold is smaller than the third threshold. It can be understood that if the current of the inductor is less than the second threshold, it means that the inductor current is small and it may be a light load situation.
  • the two switching tubes can be controlled by phase shift control without adjusting the duty cycle difference. The phase difference between the carriers of the first switching tube in the group is adjusted. If the current of the inductor is greater than the third threshold, it means that the inductor current is large and it may be overloaded.
  • the third of the two switch tube groups can be adjusted by adjusting the duty cycle without adjusting the phase difference. The duty cycle difference between a switch tube is adjusted.
  • the inductor current is greater than or equal to the second threshold and less than or equal to the third threshold, it may be an intermediate state between light load and heavy load, and the adjustment method at the previous moment can be used for adjustment. For example, if phase shifting was used at the previous moment As for the control method, continue to use the phase-shift control method; if the method of adjusting the duty cycle was used at the previous moment, continue to use the method of adjusting the duty cycle. In this way, the flying voltage can be controlled through the above three situations, so that the voltage of the controlled flying capacitor maintains a smooth transition.
  • embodiments of the present application disclose a voltage control method for a flying capacitor.
  • the flying capacitor is used in a multi-level DC converter.
  • the multi-level DC converter also includes two switch tube groups, an inductor and a control unit. device, each switch tube group includes a first switch tube and a second switch tube with complementary on and off states; the voltage control method includes: the absolute value of the difference between the sampling voltage of the flying capacitor and the reference voltage is greater than In the case of the first threshold, according to the size of the inductor current, the duty cycle difference between the first switch tubes in the two switch tube groups or the phase difference between the carrier waves of the first switch tubes in the two switch tube groups is adjusted. .
  • the duty cycle difference between the switching tubes on one side of the flying capacitor can be continued to be adjusted, or the phase difference between the switching tube carriers on that side, This controls the voltage of the flying capacitor and improves the operation stability of the multi-level DC converter.
  • the duty cycle difference between the first switch tube in the two switch tube groups is adjusted, or the duty cycle difference between the first switch tube in the two switch tube groups is adjusted.
  • the phase difference between the switching tube carriers includes: the phase difference between the first switching tube carrier in the two switching tube groups is determined and adjusted according to the size of the inductor current, and the sampling voltage of the flying capacitor is less than the reference voltage. , increasing the phase difference between the carrier waves of the first switch tube in the two switch tube groups.
  • the duty cycle difference between the first switch tube in the two switch tube groups is adjusted, or the duty cycle difference between the first switch tube in the two switch tube groups is adjusted.
  • the phase difference between the switching tube carriers includes: the phase difference between the first switching tube carrier in the two switching tube groups is determined and adjusted according to the size of the inductor current, and the sampling voltage of the flying capacitor is greater than the reference voltage. , reducing the phase difference between the carrier waves of the first switching tube in the two switching tube groups.
  • the duty cycle difference between the first switch tube in the two switch tube groups is adjusted, or the duty cycle difference between the first switch tube in the two switch tube groups is adjusted.
  • the phase difference between the switching tube carriers includes: when the inductor current is less than the second threshold, the controller adjusts the phase difference between the first switching tube carriers in the two switching tube groups.
  • the controller adjusts the duty cycle difference between the first switch tube in the two switch tube groups or the duty cycle difference between the first switch tube in the two switch tube groups according to the size of the current.
  • the phase difference between the carrier wave of a switch tube includes: in response to the current being greater than the third threshold, the controller adjusts a duty cycle difference between the first switching tubes in the two switching tube groups.
  • the controller adjusts the duty cycle difference between the first switch tube in the two switch tube groups or the duty cycle difference between the first switch tube in the two switch tube groups according to the size of the current.
  • the phase difference between a switching tube carrier includes: in response to the current being greater than or equal to the second threshold and less than or equal to the third threshold, the controller adjusts the first switch in the two switching tube groups according to the adjustment method at the previous moment.
  • control device includes a controller and a memory; wherein the memory is used to store instructions, and the controller is used to call the instructions stored in the memory to execute the method in the second aspect.
  • Figure 1 is a schematic structural diagram of a photovoltaic power generation system provided by an embodiment of the present application
  • Figure 2 is a circuit diagram of a three-level DC converter according to an embodiment of the present application.
  • Figure 3 is a schematic structural diagram of a multi-level DC converter provided by an embodiment of the present application.
  • FIGS. 4 to 9 are working mode diagrams of a three-level DC converter proposed in this application.
  • FIGS 10 to 13 are diagrams showing the relationship between the duty cycle difference, the phase difference and the flying voltage respectively proposed in this application;
  • Figure 14 is a schematic flow chart of a controller adjusting the voltage of a flying capacitor according to an embodiment of the present application
  • FIG. 15 is a schematic flowchart of a voltage control method for a flying capacitor provided by an embodiment of the present application.
  • Connection refers to direct or indirect connection.
  • a and B may be connected directly, or A and B may be connected indirectly through one or more other electrical components.
  • a and C can be directly connected, and C and B are directly connected, so that A and B are connected through C. Connection may also be called coupling, electrical connection, etc., which is not limited here.
  • the terms “first” and “second” are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.
  • the embodiment of the present application relates to a multi-level DC converter, or may be called a multi-level DC converter, which is used to perform direct current (DC)-DC power conversion.
  • a multi-level DC converter which is used to perform direct current (DC)-DC power conversion.
  • DC direct current
  • it can be a boost conversion or a multi-level DC converter.
  • Buck conversion is not specifically limited in the embodiments of this application.
  • the embodiments of the present application do not limit the application scenarios of the multi-level DC converter, and can be applied to different types of electrical equipment (such as power grids, household equipment, or industrial and commercial electrical equipment), and can be applied to user terminals (such as , mobile phones, smart devices, TVs, etc.) fields, automotive fields and other electrical equipment fields, it can be adapted to power supply scenarios for large electrical equipment (such as power grids, industrial equipment, etc.), small and medium-sized distributed electrical equipment ( For example, different application scenarios include power supply scenarios for vehicle-mounted electrical equipment, household electrical equipment, etc.) and power supply scenarios for mobile electrical equipment (such as mobile phones, smart devices, etc.).
  • FIG. 1 is a schematic architectural diagram of a photovoltaic power generation system provided in an embodiment of the present application.
  • the photovoltaic power generation system includes photovoltaic modules, multi-level DC converters, battery banks, inverter power circuit, DC load, AC load and power grid.
  • solar energy is converted into DC power by photovoltaic modules.
  • DC power is boosted through a multi-level DC converter.
  • the boosted DC power can be supplied to a DC load, or can be stored in a battery pack, or can be converted into AC power through an inverter, so that the AC power can be supplied to the AC load. Or integrated into the power grid.
  • the multi-level DC converter which can be a three-level DC converter, a five-level DC converter, a seven-level DC converter, etc.
  • the multi-level topology corresponding to the multi-level DC converter means that the output level has at least three states. For example, if the output level has three states: 1, 1/2 and 0, it is called a three-level topology. The output level has The five states of 1, 3/4, 1/2, 1/4 and 0 are called five-level topology.
  • multi-level topological circuits are divided into diode clamped multi-level topological circuits, flying capacitor clamped multi-level topological circuits, etc.
  • the topology circuit of the multi-level DC converter involved in this application may be a flying capacitor clamp type multi-level topology circuit, that is, it includes a flying capacitor.
  • FIG. 2 illustrates a three-level DC converter provided by an embodiment of the present application. circuit diagram of the device.
  • the three-level DC converter includes a high-voltage power supply V H , a capacitor C 1 , a switching tube Q 1 , a switching tube Q 2 , a switching tube Q 3 , a switching tube Q 4 , a flying capacitor C fly , and an inductor L 1.
  • the switching tube Q 1 , the switching tube Q 2 , the switching tube Q 3 and the switching tube Q 4 can be a field-effect transistor (FET) or a metal-oxide-semiconductor field-effect transistor (metal-oxide-semiconductor field- Effect transistor (MOSFET), insulated gate bipolar transistor (IGBT), junction field-effect transistor (JFET) and their parallel diodes, etc., are not limited here.
  • FET field-effect transistor
  • MOSFET metal-oxide-semiconductor field-effect transistor
  • IGBT insulated gate bipolar transistor
  • JFET junction field-effect transistor
  • the drain of the switch Q 1 is connected to the positive terminal of the high-voltage power supply V H (parallel capacitor C 1 ), and the source of the switch Q 1 is connected to the drain of the switch Q 2 and one end of the flying capacitor C fly .
  • the other end of the flying capacitor C fly is connected to the source of the switching tube Q 3 and the drain of the switching tube Q 4 .
  • the source of switch Q 2 and the drain of switch Q 3 are connected to one end of inductor L 1 , and the other end of inductor L 1 is connected to the negative terminal of low-voltage power supply V L (parallel capacitor C 2 ).
  • the switch tubes can be grouped according to the connection relationship between the flying capacitor C fly and the switching tubes to obtain two switch tube groups connected to the flying capacitor C fly .
  • switching tube Q1 and switching tube Q4 are a switching tube group
  • switching tube Q2 and switching tube Q3 are a switching tube group.
  • the switching tube connected to one end of the high-voltage power supply V H in the switching tube group is called the first switching tube.
  • the switch tube in the switch tube group connected to the other end of the high-voltage power supply V H is called the second switch tube.
  • the first switching tube is connected to the positive terminal of the high-voltage power supply V H , and the first switching tube can be the switching tube Q 1 and the switching tube Q 2 .
  • the second switching tube is connected to the negative terminal of the high-voltage power supply V H , and the second switching tube can be switching tube Q 4 and switching tube Q 3 .
  • the on and off states of the first switch tube and the second switch tube in a switch tube group are complementary.
  • the on and off states between the switching tube Q1 and the switching tube Q4 are complementary, so when the switching tube Q1 is in the on state, the switching tube Q4 is in the off state. Switch Q1 is in the off state, and switch Q4 is in the on state. In this way, the current signal can be transmitted through the carrier wave of the conductive switch tube in the first switch tube and the second switch tube in the switch tube group.
  • the on and off states of the first switch tube and the second switch tube in the same switch tube group are complementary, if the first switch tube in the switch tube group is turned off, it is necessary to control the third switch tube in the switch tube group.
  • the second switch tube is turned on. If the first switch tube in the switch tube group is closed, the second switch tube in the switch tube group needs to be controlled to be turned off.
  • the method of controlling the second switching tube in the switching tube group may refer to the method of controlling the first switching tube. The description should be adjusted accordingly.
  • the method of controlling the first switching tube in the switching tube group is described below.
  • the method of controlling the second switching tube in the switching tube group can be adjusted accordingly with reference to the description of the method of controlling the first switching tube.
  • This application uses one flying capacitor as an example. In fact, it can also be two or more. For example, another flying capacitor not shown in Figure 2 is connected in series with the flying capacitor C fly . Or there may be two flying capacitors in the five-level DC converter.
  • One flying capacitor is connected in parallel with the first switching tube group and the second switching tube group.
  • the second switching tube group includes the first sub-switch group and the second switching tube group.
  • the first sub-switch group and the second sub-switch group are connected in parallel with another flying capacitor.
  • the multi-level DC converter may also include capacitors, resistors, etc. connected to the inductor.
  • the three-level DC converter may also include the controller 101 in FIG. 3 for controlling the switching tube group.
  • the controller 101 can be a pulse width modulation (PWM) device, or a battery management system (BMS) based on PWM technology, a micro control unit (MCU), or a central processing unit (central processing unit).
  • processing unit CPU
  • other general-purpose processors DSP
  • application specific integrated circuits ASICs
  • off-the-shelf programmable gate arrays field-programmable gate arrays, FPGAs
  • Other programmable logic devices discrete gate or transistor logic devices, discrete hardware components, etc.
  • the controller can be understood as a chip or multiple chips with communication connections.
  • the controller may include a control unit corresponding to each switch tube, or may include a control unit corresponding to the switch tube group, for example, a pulse width modulator corresponding to switch tube Q 1 and switch tube Q 4 , switch tube Q 2 and switch tube Q 3The corresponding pulse width modulator, etc. are not limited here.
  • the carrier waves of switching tubes Q 1 , Q 2 , Q 3 and Q 4 can be modulated, and the on and off states of the switching tubes can be controlled to achieve real-time bidirectional flow of power.
  • the input terminal of the three-level DC converter is the high-voltage power supply V H and the output terminal is the low-voltage power supply V L .
  • the current of the three-level DC converter flows from the high-voltage power supply V H Power supply V H flows to low voltage power supply V L .
  • the input terminal of the three-level DC converter is the low-voltage power supply V L and the output terminal is the high-voltage power supply V H .
  • the current of the three-level DC converter flows from the low-voltage power supply V H Power supply V L flows to high voltage power supply V H .
  • the charging and discharging time of the flying capacitor can be adjusted to control the voltage of the flying capacitor. For example, when the switching tube Q 1 and the switching tube Q 3 are turned on, the high-voltage power supply V H acts on the low-voltage power supply V L through the switching tube Q 1 , the switching tube Q 3 and the inductor L 1 .
  • the flying capacitor C fly is charged and the voltage rises; if the current of the inductor L 1 flows from the low-voltage power supply V L to the high-voltage voltage V H (the direction of the current is negative) ), the flying capacitor C fly is discharged and the voltage decreases; when the switching tube Q 2 and the switching tube Q 4 are turned on, the flying capacitor C fly acts on the low-voltage power supply through the switching tube Q 2 , the switching tube Q 4 and the inductor L 1 On V L , if the current direction of the inductor L 1 is positive, the flying capacitor C fly is discharged and the voltage decreases; if the current direction of the inductor L 1 is negative, the flying capacitor C fly is charged and the voltage increases.
  • the voltage of the flying capacitor C fly may be referred to as the flying voltage, and the current of the inductor may be referred to as the inductor current.
  • the inductor current is relatively small and the inductor current is a high-frequency triangular wave that repeatedly switches between positive and negative, this situation can be called light load.
  • the inductor current is relatively large, and the inductor current is always positive or always negative. This situation can be called heavy load.
  • the difference in duty cycle can be referred to as duty cycle difference, and the difference in phase shift or phase can be referred to as phase difference.
  • the method of phase shift control is to adjust the phase under the premise of fixed duty cycle.
  • the method of adjusting the duty cycle is to adjust the duty cycle under the premise of fixing the phase. In this way, the singleness of the adjustment can be improved and the affected voltage can be guaranteed to change smoothly.
  • the duty ratios of switching tube Q 1 (switching tube Q 3 ) and switching tube Q 2 (switching tube Q 4 ) are equal, and the phase is shifted by 180°, that is, the switching tube Q 1 carrier
  • the phase difference between the carrier wave of switching tube Q2 is 180°. Therefore, the steady-state operation of the three-level DC converter can be achieved by adjusting the difference in duty cycle between switching tube Q1 and switching tube Q2 (which can be referred to as the duty cycle difference for short).
  • the duty cycle of the switching tube Q 1 can be increased and the duty cycle of the switching tube Q 2 can be reduced.
  • the duty cycle is to increase the duty cycle difference between switch tube Q 1 and switch tube Q 2 to increase the fly-over voltage, and conversely reduce the fly-over voltage; when the power changes from low-voltage power supply V L to high-voltage power supply V H
  • the duty cycle difference between tubes Q2 can increase the flying voltage, and vice versa can reduce the flying voltage.
  • the flying capacitor under light load conditions, controlling the voltage of the flying capacitor according to the instantaneous current direction places extremely high demands on the control chip and cannot be applied in actual projects. Even if the flying capacitor is connected in parallel to the first switching tube (for example, switching tube Q 1 and switching tube Q 2 ) or the second switching tube (for example, switching tube Q 3 and switching tube Q 4 ) in the switching tube group, the duty cycle of the switching tube is If the difference in ratio is adjusted very large, the voltage of the flying capacitor cannot be effectively increased or decreased, and the control goal of stabilizing the voltage of the flying capacitor at the target value cannot be achieved.
  • the first switching tube for example, switching tube Q 1 and switching tube Q 2
  • the second switching tube for example, switching tube Q 3 and switching tube Q 4
  • this application proposes a multi-level DC converter.
  • the controller in the multi-level DC converter is used when the absolute value of the difference between the sampling voltage of the flying capacitor and the reference voltage is greater than the first threshold.
  • the duty cycle difference between the first switch tubes in the two switch tube groups or the phase difference between the carrier waves of the first switch tubes in the two switch tube groups is adjusted.
  • the sampling voltage of the flying capacitor is the collected real-time voltage.
  • the reference voltage of the flying capacitor is the target value to be adjusted for the flying capacitor.
  • the target value of the three-level DC converter can be 1/2 times the voltage of the high-voltage power supply.
  • the current of the inductor also known as the inductor current, can be the instantaneous current value or the average value.
  • This application does not limit the first threshold, and it can be 0, etc. It can be understood that if the absolute value of the difference between the sampling voltage of the flying capacitor and the reference voltage is greater than the first threshold, it means that the voltage of the flying capacitor has not been adjusted to the target value, and the parallel connection on the flying capacitor side can be continued.
  • the duty cycle difference between the switching tubes or the phase difference between the carrier waves of the first switching tube on this side is used to control the voltage of the flying capacitor, which can reduce the voltage stress of the multi-level DC converter. If the difference between the sampling voltage of the flying capacitor and the reference voltage is less than or equal to the first threshold, it means that the voltage of the flying capacitor has been adjusted to the target value, and the current working state can be maintained to continue working. In this way, the operation stability of the multi-level DC converter can be improved.
  • This application does not limit the method of adjusting the phase difference and the duty cycle difference.
  • the adjustment method according to the current direction can be used. Make adjustments. For example, when current flows from a high-voltage power supply to a low-voltage power supply, if the sampling voltage of the flying capacitor C fly is less than the reference voltage, the duty cycle difference between the first switching tube in the two switching tube groups can be increased.
  • the duty cycle difference between the first switch tube in the two switch tube groups can be reduced, that is, the duty cycle of switch tube Q1 is reduced and the duty cycle of switch tube Q2 is increased. ratio to reduce the flying voltage; or when the current flows from the low-voltage power supply to the high-voltage power supply, if the sampling voltage of the flying capacitor C fly is less than the reference voltage, the first switching tube in the two switching tube groups can be reduced.
  • the duty cycle difference between them is to reduce the duty cycle of switching tube Q1 and increase the duty cycle of switching tube Q2 to increase the flyover voltage; or when the current flows from the low-voltage power supply to the high-voltage power supply, If the sampling voltage of the flying capacitor C fly is greater than the reference voltage, the gap between the first switch tube in the two switch tube groups can be increased.
  • the duty cycle difference is to increase the duty cycle of switching tube Q1 and reduce the duty cycle of switching tube Q2 to reduce the flyover voltage. In this way, when deciding to adjust the duty cycle difference, the voltage across the flying capacitor C fly is adjusted according to the direction of the inductor current.
  • the principle of adjusting the phase difference of the flying capacitor C fly is to increase the phase difference between the carrier waves of the first switch tube (or the second switch tube), so that the charging time (area) of the flying capacitor C fly is greater than the discharge time (area) , thereby increasing the voltage of the flying capacitor C fly ; reducing the phase difference between the carrier waves of the first switching tube (or the second switching tube), so that the charging time (area) of the flying capacitor C fly is less than the discharging time (area) , thereby reducing the voltage across the flying capacitor C fly . Therefore, in a possible example, the phase difference between the first switching tube carrier in the two switching tube groups is determined and adjusted according to the size of the inductor current, and the sampling voltage of the flying capacitor C fly is less than the reference voltage.
  • FIGS. 4 to 9 are respectively diagrams of the working modes of a three-level DC converter proposed in this application.
  • V 0 is the flying voltage V fly at the beginning of a cycle
  • V 1 is the flying voltage V fly at any time in a cycle
  • V 2 is the flying voltage V fly at the end of a cycle
  • IL is The inductor current is also described by i(t) in the formula below
  • N/A/B/C/M are the peak values of the inductor current IL respectively
  • T 0 ⁇ T 3 are the time points at different stages in a switching cycle , considering that the dead zone d causes different freewheeling loops in different modes, the values of T 0 ⁇ T 3 are different
  • m/k/n are the slopes of the corresponding straight lines in the figure.
  • D 1 is the duty cycle of the switching tube Q 1
  • D 2 is the duty cycle of the switching tube Q 2 .
  • the duty cycle D of the three-level DC converter can be understood as the steady-state duty cycle of the converter under ideal circumstances. Under ideal circumstances, the duty cycle D of the three-level DC converter is equal to the duty cycle of the switching tube Q 1 Ratio D 1 , and equal to the duty cycle D 2 of switching tube Q 2 . In fact, because the flying voltage deviates from the target value, it is necessary to adjust the duty cycle difference between switching tube Q1 and switching tube Q2 , or the phase difference between the carrier wave of switching tube Q1 and switching tube Q2 .
  • duty cycle D is less than 0.5, it means that the duty cycle D 1 of the switching tube Q 1 and the duty cycle D 2 of the switching tube Q 2 are both less than 0.5. If the duty cycle D is greater than 0.5, it means that the duty cycle D 1 of the switching tube Q 1 and the duty cycle D 2 of the switching tube Q 2 are both greater than 0.5.
  • Figures 4 to 9 respectively correspond to Mode 1, Mode 2, Mode 3, Mode 4, Mode 5 and Mode 6, among which:
  • the duty cycle D is less than 0.5, and the inductor current I L is always positive, which is a heavy load situation.
  • the duty cycle D is less than 0.5, and the inductor current I L (t) can be negative or positive, which is a light load situation.
  • the duty cycle D is greater than 0.5, and the inductor current IL can be negative or positive, which is a light load situation.
  • the dead zone d can be merged into the duty cycle D 1 and the duty cycle D 2 .
  • Unified analysis Combined with the freewheeling circuit of the inductor current in Figures 7 to 9, in modes four, five, and six, the dead zone d can be merged into the duty cycle D 1 and the duty cycle D 2 for unified analysis.
  • the following takes Mode 1 and Mode 4 as examples for analysis, and other modes can be deduced by analogy.
  • the values of m, n, and k can refer to the following formula.
  • L in the formula is the size of the inductor.
  • duty cycle D of fixed duty cycle D 1 and duty cycle D 2 can be any fixed value from 0 to 1.
  • adjust the The phase difference between the carrier wave of switch Q 1 (or switch Q 4 ) and switch Q 2 (or switch Q 3 ) is ⁇ .
  • the influence of different phase differences on the flying voltage can be obtained, that is, the phase shift control has Effect of flying voltage.
  • FIGS. 10 to 13 are respectively diagrams of the relationship between the duty cycle difference, the phase difference and the flying voltage proposed in this application.
  • Figure 10 and Figure 11 are used to describe the influence of different loads on the change of fly-over voltage under the condition of fixed phase difference and fixed duty cycle difference.
  • the horizontal axis is the inductor current IL and the vertical axis is The change amount of fly voltage ⁇ V fly .
  • the solid line corresponding to the fixed duty cycle difference reflects the adjustment strength of the flying capacitor voltage under different loads by adjusting the same duty cycle difference for the first switch tube.
  • the dotted line corresponding to the fixed phase difference reflects the adjustment strength of the flying capacitor voltage under different loads by adjusting the same phase difference to the first switch tube.
  • the inductor current can be a high-frequency triangular wave, switching repeatedly between positive and negative, and the value is small, it can be the part where the dotted line is larger than the solid line in the figure and is close to 0 value
  • the change value of flying voltage is small.
  • adjusting the duty cycle will cause the flying voltage to change in the opposite direction.
  • the change value of the flying voltage gradually increases, so that the duty cycle can be adjusted under heavy load to control the flying voltage.
  • the method of adjusting the duty cycle will quickly weaken the control of the flying voltage as the load gradually decreases.
  • the control strength of phase-shift control is relatively strong under light load and relatively weak under heavy load, so that phase-shift control can be performed under light load, that is, the phase difference is adjusted to achieve control of the flying voltage.
  • Figures 12 and 13 are used to describe the impact of a fixed duty cycle difference and a fixed phase difference on the change of the flying voltage under a fixed load.
  • the horizontal axis is the duty cycle D, and the vertical axis is the change of the flying voltage.
  • Figure 12 is applied under heavy load
  • Figure 13 is applied under light load. It can be seen from Figure 12 and Figure 13 that the phase-shift control method gradually weakens the control strength of the flying voltage as the duty cycle gradually increases. However, under light load, the phase-shift control method can maintain greater adjustment strength than the method of adjusting the duty cycle. In this way, under light load, the flying voltage control can be achieved using the phase-shift control method. Under heavy load, the method of adjusting the duty cycle can be used to control the flying voltage.
  • the controller is specifically configured to adjust the phase difference between the first switching tube carriers in the two switching tube groups in response to the inductor current being less than the second threshold.
  • the controller is specifically configured to adjust the duty cycle difference between the first switch tubes in the two switch tube groups in response to the inductor current being greater than the third threshold.
  • the controller is specifically configured to adjust the duty cycle between the first switching tubes in the two switching tube groups according to the adjustment method at the previous moment in response to the inductor current being greater than or equal to the second threshold and less than or equal to the third threshold. difference, or the phase difference between the carrier wave of the first switch tube in the two switch tube groups.
  • This application does not limit the size of the second threshold and the third threshold, and the second threshold is smaller than the third threshold. It's understandable, If the current of the inductor is less than the second threshold, it means that the inductor current is small and it may be a light load situation. Without adjusting the duty cycle difference, the phase shift control method can be used to control the switching of the two switch tube groups. The phase difference between the carrier waves of the first switching tube is adjusted. If the current of the inductor is greater than the third threshold, it means that the inductor current is large and it may be overloaded. The third of the two switch tube groups can be adjusted by adjusting the duty cycle without adjusting the phase difference. The duty cycle difference between a switch tube is adjusted.
  • the inductor current is greater than or equal to the second threshold and less than or equal to the third threshold, it may be an intermediate state between light load and heavy load, and the adjustment method at the previous moment can be used for adjustment. For example, if phase shifting was used at the previous moment As for the control method, continue to use the phase-shift control method; if the method of adjusting the duty cycle was used at the previous moment, continue to use the method of adjusting the duty cycle. In this way, the flying voltage can be controlled through the above three situations, so that the voltage of the controlled flying capacitor maintains a smooth transition.
  • the controller may include a hysteresis module, a first pulse width modulator and a second pulse width modulator connected to the hysteresis module.
  • the first pulse width modulator is used to adjust the phase or duty cycle of the first switch tube (or the second switch tube) in a switch tube group connected to the flying capacitor
  • the second pulse width modulator is used to adjust the phase with the flying capacitor.
  • the first pulse width modulator is used to adjust the phase or duty cycle of the switching tube Q1 or the switching tube Q4
  • the second pulse width modulator is used to adjust the phase or duty cycle of the switching tube Q2 or the switching tube Q3
  • the hysteresis module may include a duty cycle controller and a phase controller.
  • the duty cycle controller is used to control the first pulse width modulator and the second pulse width modulator to execute a duty cycle control loop to realize the switching between the two switching tubes. adjustment of the duty cycle difference between.
  • the phase controller is used to control the first pulse width modulator and the second pulse width modulator to execute a phase control loop to adjust the phase difference between the two switch tube carriers.
  • the hysteresis module is used to control the adjustment of the first pulse width modulator and the second pulse width modulator according to the size of the inductor current in response to the absolute value of the difference between the sampling voltage of the flying capacitor and the reference voltage being greater than the first threshold.
  • the hysteresis module is specifically used to determine and adjust the phase difference between the first switching tube carriers in the two switching tube groups according to the size of the inductor current. If the sampling voltage of the flying capacitor is less than the reference voltage, the two switching tubes will be increased. The phase difference between the carrier waves of the first switching tube in the switching tube group. Or if the sampling voltage of the flying capacitor is greater than the reference voltage, the phase difference between the carrier waves of the first switching tube in the two switching tube groups is reduced.
  • the hysteresis module is specifically used to determine and adjust the duty cycle difference between the first switch tubes in the two switch tube groups according to the size of the inductor current. If the current flows from the high-voltage power supply to the low-voltage power supply, and the flying capacitor If the sampling voltage is less than the reference voltage, increase the duty cycle difference between the first switch tube in the two switch tube groups; or if the current flows from the high-voltage power supply to the low-voltage power supply and the sampling voltage of the flying capacitor is greater than the reference voltage, then Reduce the duty cycle difference between the first switch tube in the two switch tube groups; or if the current flows from the low-voltage power supply to the high-voltage power supply and the sampling voltage of the flying capacitor is less than the reference voltage, then reduce the duty cycle difference between the two switch tube groups.
  • the duty cycle difference between the first switch tubes in the The duty cycle difference between them.
  • the hysteresis module is specifically configured to control the first pulse width modulator and the second pulse width modulator to adjust the phase difference between the first switching tube carriers in the two switching tube groups in response to the current being less than the second threshold; or in response to The current is greater than the third threshold, and the first pulse width modulator and the second pulse width modulator are controlled to adjust the duty cycle difference between the first switching tubes in the two switching tube groups; or in response to the current being greater than or equal to the second threshold , and less than or equal to the third threshold, the first pulse width modulator and the second pulse width modulator are controlled according to the adjustment method at the previous moment to adjust the phase between the first switching tube carriers in the two switching tube groups. The difference or the duty cycle difference between the first switching tube in the two switching tube groups.
  • Figure 14 is a schematic flow chart of a controller provided by the present application to adjust the voltage of the flying capacitor.
  • the hysteresis module may first determine whether the absolute value of the difference between the sampling voltage V fly_ad of the flying capacitor and the reference voltage V fly_ref of the flying capacitor is greater than the first threshold. If so, and the average value of the inductor current i LAVG is less than the second threshold, the corresponding phase shift of the phase controller can be controlled under the premise that the control duty cycle remains unchanged (the output limit of the duty cycle control loop changes linearly to zero).
  • the control loop operates so that the first pulse width modulator applies the output result of the current duty cycle control loop to the steady-state duty cycle according to the direction of the inductor current.
  • the second pulse width modulator then adds the output result of the phase shift control loop to the carrier wave of the switching tube corresponding to the second pulse width modulator, so that the switching tube Q1 corresponding to the first pulse width modulator and the second pulse width modulator
  • the phase difference between the switching tube Q2 carrier corresponding to the wide modulator is dynamically adjusted around 180°.
  • the duty cycle control loop corresponding to the duty cycle controller can be controlled to operate under the premise that the control phase difference remains unchanged, so that the first pulse width modulator and the second pulse width modulator, According to the direction of the inductor current, the output result of the current phase shift control loop is applied to the carrier corresponding to the second pulse width modulator, so that the duty cycle difference between the switching tube Q 1 and the switching tube Q 2 is dynamically adjusted near 0 .
  • the adjustment method at the previous moment is maintained to control the corresponding phase shift control loop of the phase controller to work, so that the first pulse width modulator and the second pulse width modulator adjust the switch.
  • phase ratio difference between the carrier wave of tube Q1 and switch tube Q2 , or the duty cycle control loop corresponding to the duty cycle controller is controlled to work, so that the first pulse width modulator and the second pulse width modulator adjust the switching tube
  • the duty cycle difference between Q 1 and switch Q 2 is controlled to work, so that the first pulse width modulator and the second pulse width modulator adjust the switching tube.
  • FIG. 15 is a flow chart of a voltage control method for a flying capacitor provided by this application.
  • the flying capacitor can be used in a multi-level DC converter as shown in Figure 3.
  • the multi-level DC converter includes at least one flying capacitor, two switch tube groups connected to the flying capacitor, and each switch.
  • An inductor connected to the positive terminal of the tube bank and the low-voltage voltage of the multilevel DC converter, and a controller for controlling the switching tube bank.
  • Each switch tube group includes a first switch tube and a second switch tube whose on and off states are complementary.
  • the voltage control method may include step S101, where:
  • the absolute value of the difference between the sampling voltage of the flying capacitor and the reference voltage is greater than the first threshold, it means that the voltage of the flying capacitor has not been adjusted to the target value, and the parallel connection on the flying capacitor side can be continued.
  • the phase difference between the switching tubes, or the duty cycle difference between the switching tubes on this side is used to control the voltage of the flying capacitor and improve the operation stability of the multi-level DC converter.
  • the duty cycle difference between the first switch tubes in the two switch tube groups is adjusted, or the duty cycle difference between the first switch tube carriers in the two switch tube groups is adjusted.
  • the phase difference method may include the following steps: determining and adjusting the phase difference between the carrier waves of the first switch tube in the two switch tube groups according to the size of the inductor current, and when the sampling voltage of the flying capacitor is less than the reference voltage, Increase the phase difference between the first switching tube carriers in the two switching tube groups; or adjust the phase difference between the first switching tube carriers in the two switching tube groups according to the size of the inductor current, and fly across When the sampling voltage of the capacitor is greater than the reference voltage, the phase difference between the carrier waves of the first switching tube in the two switching tube groups is reduced. In this way, by increasing the phase difference between the carrier wave of the first switch tube in the two switch tube groups, the The voltage across the flying capacitor. The voltage across the flying capacitor is reduced by reducing the phase difference between the carrier waves of the first switch in the
  • the duty cycle difference between the first switch tubes in the two switch tube groups is adjusted, or the duty cycle difference between the first switch tube carriers in the two switch tube groups is adjusted.
  • the phase difference method may include the following steps: when determining and adjusting the duty cycle difference between the first switching tubes in the two switching tube groups according to the size of the inductor current, if the current flows from the high-voltage power supply to the low-voltage power supply, and If the sampling voltage of the flying capacitor is less than the reference voltage, the duty cycle difference between the first switching tube in the two switching tube groups is increased; or if the current flows from the high-voltage power supply to the low-voltage power supply, and the sampling voltage of the flying capacitor is greater than Reference voltage, then reduce the duty cycle difference between the first switch tube in the two switch tube groups; or if the current flows from the low-voltage power supply to the high-voltage power supply, and the sampling voltage of the flying capacitor is less than the reference voltage, then reduce the duty cycle difference between the two
  • the duty cycle difference between the first switch tubes in the two switch tube groups or the phase between the carrier waves of the first switch tubes in the two switch tube groups is adjusted.
  • the difference method may include the following steps: when the inductor current is less than the second threshold, adjust the phase difference between the first switch carriers in the two switch groups; or when the inductor current is greater than the third threshold , adjust the duty cycle difference between the first switch tubes in the two switch tube groups; or when the inductor current is greater than or equal to the second threshold and less than or equal to the third threshold, according to the adjustment method at the previous moment Adjust the duty cycle difference between the first switching tubes in the two switching tube groups or the phase difference between the carrier waves of the first switching tubes in the two switching tube groups. In this way, the flying voltage can be controlled through the above three situations, so that the voltage of the controlled flying capacitor maintains a smooth transition.
  • the embodiment of the present application also discloses a control device.
  • the control device includes a controller and a memory; the memory is used to store instructions, and the controller is used to call the instructions stored in the memory to execute the method in any of the above aspects.
  • the aforementioned program can be stored in a computer-readable storage medium.
  • the aforementioned storage media includes: mobile storage devices, read-only memory (read-only memory, ROM), random access memory (random access memory, RAM), magnetic disks or optical disks, etc.

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Abstract

本申请实施例提供一种多电平直流变换器和飞跨电容的电压控制方法、控制装置。其中，多电平直流变换器包括控制器、飞跨电容、两个开关管组和电感。飞跨电容的控制方法包括：响应于飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值，根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差或两个开关管组中的第一开关管载波之间的相位差。采用本申请实施例，可以对飞跨电容的电压进行控制，提高了多电平直流变换器运行的稳定性。

Description

多电平直流变换器和飞跨电容的电压控制方法、控制装置
本申请要求于2022年06月23日提交中国专利局、申请号为202210715575.6、申请名称为“多电平直流变换器和飞跨电容的电压控制方法、控制装置”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，尤其涉及一种多电平直流变换器和飞跨电容的电压控制方法、控制装置。
背景技术
多电平直流变换器通过增加飞跨电容，可降低输入电压在各开关管上的电压应力。以带有飞跨电容的三电平直流变换器为例，可以通过飞跨电压储存一半输入电压，使得输出电平有0、1/2和1三种，其变化幅度为两电平拓扑的一半，进而可以使用低耐压的开关管来提升电子系统的性能。
目前，可以通过判断电感的电流方向，调整开关管组中的第一开关管(或第二开关管)之间的占空比的差值，来调整飞跨电容的充放电时间，以实现对飞跨电容的电压进行控制。但是在电感电流很小，电感电流为高频三角波在正负之间反复切换的情况下，根据瞬时的电流方向控制飞跨电容的电压，对控制芯片有极高的要求，无法适用于实际的工程中。即便将开关管组中的第一开关管(或第二开关管)之间的占空比的差值调的很大，也无法将飞跨电压有效地升高或者降低，达不到将飞跨电容的电压稳定在目标值的控制目标。
发明内容
本申请实施例公开了一种多电平直流变换器和飞跨电容的电压控制方法、控制装置，可以对飞跨电容的电压进行控制，提高了多电平直流变换器运行的稳定性。
第一方面，本申请实施例公开了一种多电平直流变换器，该多电平直流变换器包括至少一个飞跨电容、与飞跨电容连接的两个开关管组、与各个开关管组和多电平直流变换器的低压电源的正极端连接的电感，以及用于控制开关管组的控制器；其中，开关管组均包括导通和关断状态互补的第一开关管和第二开关管，第一开关管连接多电平直流变换器的高压电源的一端，第二开关管连接多电平直流变换器的高压电源的另一端；控制器用于在飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值的情况下，根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差或两个开关管组中的第一开关管载波之间的相位差。
其中，多电平直流变换器，或者可以称为多电平直流转换器，用于进行直流(direct current，DC)-直流的电能变换，例如，可以升压变换，也可以降压变换。本申请对于多电平直流变 换器的具体类型不做限定，可以为三电平直流变换器、五电平直流变换器、七电平直流变换器等。多电平直流变换器对应的多电平拓扑是指输出电平至少有三种状态，例如，输出电平有1、1/2和0三种状态则称为三电平拓扑，输出电平有1、3/4、1/2、1/4和0五种状态则称为五电平拓扑。
第一开关管和第二开关管可以为场效应管(field-effect transistor，FET)、金属氧化物半导体场效应管(metal-oxide-semiconductor field-effect transistor，MOSFET)、绝缘栅双极型晶体管(insulated gate bipolar transistor，IGBT)、结型场效应管(junction field-effect transistor，JFET)及其并联二极管等，在此不作限定。
控制器可以为脉宽调制(pulse width modulation，PWM)器、或者基于PWM技术的电池管理系统(battery management system，BMS)、微控制单元(micro control unit，MCU)、中央处理单元(central processing unit，CPU)、其他通用处理器、数字信号处理器(digital signal processor，DSP)、专用集成电路(application specific integrated circuit，ASIC)、现成可编程门阵列(field-programmable gate array，FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件等。该控制器可以是一个芯片或者多个具有通信连接的芯片。控制器可以包括各个开关管分别对应的控制单元，或者可以包括开关管组对应的控制单元，例如，开关管组中的第一开关管和第二开关管对应的脉宽调制器等，在此不做限定。
飞跨电容的采样电压是采集到的实时电压。飞跨电容的参考电压是飞跨电容待调整的目标值。电感的电流或称为电感电流，可以为瞬时的电流值或平均值。
本申请对于第一阈值不做限定，可以为0等。可以理解，若飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值，则表示飞跨电容的电压还未调整为目标值(例如，三电平直流变换器的目标值可以为1/2倍的高压电源的电压)，可以继续调整飞跨电容一侧的开关管之间的占空比差，或该侧的第一开关管载波之间的相位差，从而对飞跨电容的电压进行控制，可以减小多电平直流变换器的电压应力。若飞跨电容的采样电压和参考电压之间的差值小于或等于第一阈值，则表示飞跨电容的电压已调整为目标值，可以保持当前的工作状态继续工作。如此，可以提高多电平直流变换器运行的稳定性。
结合第一方面，在第一种可能的实现方式中，控制器具体用于在根据电感电流的大小确定调整两个开关管组中的第一开关管载波之间的相位差，且飞跨电容的采样电压小于参考电压的情况下，增大两个开关管组中的第一开关管载波之间的相位差。如此，可以升高飞跨电容的电压。
结合第一方面，在第二种可能的实现方式中，控制器具体用于在根据电感电流的大小确定调整两个开关管组中的第一开关管载波之间的相位差，且飞跨电容的采样电压大于参考电压的情况下，减小两个开关管组中的第一开关管载波之间的相位差。如此，可以减小飞跨电容的电压。
结合第一方面，或者第一种可能的实现方式，或者第二种可能的实现方式，在第三种可能的实现方式中，控制器具体用于在电感电流小于第二阈值的情况下，调整两个开关管组中的第一开关管载波之间的相位差。
结合第一方面，在第四种可能的实现方式中，控制器具体用于在电感电流大于第三阈值的情况下，调整两个开关管组中的第一开关管之间的占空比差。
结合第一方面，或者第一种可能的实现方式，或者第二种可能的实现方式，在第五种可能的实现方式中，控制器具体用于在电感电流大于或等于第二阈值，且小于或等于第三阈值的情况下，根据上一时刻的调整方法调整两个开关管组中的第一开关管之间的占空比差或两个开关管组中的第一开关管载波之间的相位差。
本申请对于第二阈值和第三阈值的大小不做限定，第二阈值小于第三阈值。可以理解，若电感的电流小于第二阈值，则表示电感电流较小，可能为轻载的情况，可以在不调整占空比差的前提下，通过移相控制的方法，对两个开关管组中的第一开关管载波之间的相位差进行调整。若电感的电流大于第三阈值，则表示电感电流较大，可能为重载的情况，可以在不调整相位差的前提下，通过调整占空比的方法，对两个开关管组中的第一开关管之间的占空比差进行调整。若电感的电流大于或等于第二阈值，且小于或等于第三阈值，可能为轻载和重载的中间状态，可以采用上一时刻的调整方式进行调整，例如，若上一时刻采用移相控制的方法，则继续采用移相控制的方法；若上一时刻采用调整占空比的方法，则继续采用调整占空比的方法。如此，可以通过以上三种情况实现飞跨电压的控制，使得控制的飞跨电容的电压保持平滑过渡。
第二方面，本申请实施例公开了一种飞跨电容的电压控制方法，飞跨电容应用于多电平直流变换器中，多电平直流变换器还包括两个开关管组、电感和控制器，各个开关管组均包括导通和关断状态互补的第一开关管和第二开关管；电压控制方法包括：在飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值的情况下，根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差或两个开关管组中的第一开关管载波之间的相位差。如此，可以在确定飞跨电容的电压未调整至目标值的情况下，继续调整飞跨电容一侧的开关管之间的占空比差，或该侧的开关管载波之间的相位差，从而对飞跨电容的电压进行控制，提高了多电平直流变换器运行的稳定性。
结合第二方面，第一种可能的实现方式中，根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差，或两个开关管组中的第一开关管载波之间的相位差，包括：在根据电感电流的大小确定调整两个开关管组中的第一开关管载波之间的相位差，且飞跨电容的采样电压小于参考电压的情况下，增大两个开关管组中的第一开关管载波之间的相位差。
结合第二方面，第二种可能的实现方式中，根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差，或两个开关管组中的第一开关管载波之间的相位差，包括：在根据电感电流的大小确定调整两个开关管组中的第一开关管载波之间的相位差，且飞跨电容的采样电压大于参考电压的情况下，减小两个开关管组中的第一开关管载波之间的相位差。
结合第二方面，第三种可能的实现方式中，根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差，或两个开关管组中的第一开关管载波之间的相位差，包括：在电感电流小于第二阈值的情况下，控制器调整两个开关管组中的第一开关管载波之间的相位差。
结合第二方面，第四种可能的实现方式中，控制器根据电流的大小，调整两个开关管组中的第一开关管之间的占空比差，或两个开关管组中的第一开关管载波之间的相位差， 包括：响应于电流大于第三阈值，控制器调整两个开关管组中的第一开关管之间的占空比差。
结合第二方面，第五种可能的实现方式中，控制器根据电流的大小，调整两个开关管组中的第一开关管之间的占空比差，或两个开关管组中的第一开关管载波之间的相位差，包括：响应于电流大于或等于第二阈值，且小于或等于第三阈值，控制器根据上一时刻的调整方法调整两个开关管组中的第一开关管之间的占空比差或两个开关管组中的第一开关管载波之间的相位差。
第三方面，本申请实施例公开了一种控制装置。该控制装置包括控制器和存储器；其中，存储器用于存储指令，控制器用于调用该存储器中存储的指令，执行第二方面中的方法。
应理解的是，本申请上述多个方面的实现和有益效果可互相参考。
附图说明
以下对本申请实施例用到的附图进行介绍。
图1为本申请实施例提供的一种光伏发电系统的架构示意图；
图2为本申请实施例提供一种三电平直流变换器的电路图；
图3为本申请实施例提供的一种多电平直流变换器的结构示意图；
图4～图9为本申请提出的一种三电平直流变换器的工作模式图；
图10～图13为分别为本申请提出的占空比差和相位差与飞跨电压之间的关系图；
图14为本申请实施例提供的一种控制器调整飞跨电容的电压的流程示意图；
图15为本申请实施例提供的一种飞跨电容的电压控制方法的流程示意图。
具体实施方式
本申请中所描述的“连接”指的是直接或间接连接。例如，A与B连接，既可以是A与B直接连接，也可以是A与B之间通过一个或多个其它电学元器件间接连接。例如，可以是A与C直接连接，C与B直接连接，从而使得A与B之间通过C实现了连接。连接还可以称为耦合，或电连接等，在此不做限定。术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性。
本申请实施例涉及一种多电平直流变换器，或者可以称为多电平直流转换器，用于进行直流(direct current，DC)-直流的电能变换，例如，可以升压变换，也可以降压变换，本申请实施例对此不做具体限定。且本申请实施例对于多电平直流变换器的应用场景不做限定，可以适用于不同类型的用电设备(如电网、家用设备或者工业和商业用电设备)，可应用于用户终端(例如，手机、智能设备、电视机等)领域、汽车领域等用电设备领域，可适配于为大型用电设备(例如，电网、工业设备等)的供电场景、中小型分布式用电设备(例如，车载用电设备、家庭用电设备等)的供电场景以及移动用电设备(例如，手机、智能设备等)供电场景等不同应用场景。
示例性地，请参阅图1，图1为本申请实施例中提供的一种光伏发电系统的架构示意图。如图1所示，该光伏发电系统包括光伏组件、多电平直流变换器、蓄电池组、逆变电 路、直流负载、交流负载以及电网。在该光伏发电系统中，太阳能被光伏组件转换成直流电能。直流电能通过多电平直流变换器进行升压，升压后的直流电能可以供给直流负载，或者可以存储至蓄电池组中，或者可以通过逆变器转换成交流电能，以使交流电能供给交流负载或并到电网中。
本申请对于多电平直流变换器的具体类型不做限定，可以为三电平直流变换器、五电平直流变换器、七电平直流变换器等。多电平直流变换器对应的多电平拓扑是指输出电平至少有三种状态，例如，输出电平有1、1/2和0三种状态则称为三电平拓扑，输出电平有1、3/4、1/2、1/4和0五种状态则称为五电平拓扑。此外，多电平拓扑电路又分为二极管钳位型多电平拓扑电路、飞跨电容钳位型多电平拓扑电路等形式。本申请中涉及的多电平直流变换器的拓扑电路可以为飞跨电容钳位型多电平拓扑电路，即包括飞跨电容。
为了使本领域技术人员更好地理解本申请实施例提供的技术方案，下面以三电平直流变换器为例，请参照图2，图2为本申请实施例提供一种三电平直流变换器的电路图。如图2所示，三电平直流变换器包括高压电源VH、电容C1、开关管Q1、开关管Q2、开关管Q3、开关管Q4、飞跨电容Cfly、电感L1、电容C2和低压电源VL。
其中，开关管Q1、开关管Q2、开关管Q3和开关管Q4可以为场效应管(field-effect transistor，FET)、金属氧化物半导体场效应管(metal-oxide-semiconductor field-effect transistor，MOSFET)、绝缘栅双极型晶体管(insulated gate bipolar transistor，IGBT)、结型场效应管(junction field-effect transistor，JFET)及其并联二极管等，在此不作限定。
开关管Q1的漏极与高压电源VH(并联的电容C1)的正极端连接，开关管Q1的源极与开关管Q2的漏极和飞跨电容Cfly的一端连接。飞跨电容Cfly的另一端连接开关管Q3的源极和开关管Q4的漏极。开关管Q2的源极和开关管Q3的漏极连接电感L1的一端，电感L1的另一端与低压电源VL(并联的电容C2)的负极端连接。
在本申请实施例中，可以根据飞跨电容Cfly与开关管之间的连接关系，将开关管进行分组，得到与飞跨电容Cfly连接的两个开关管组。例如，开关管Q1和开关管Q4为一个开关管组，开关管Q2和开关管Q3为一个开关管组。进一步的，还可以根据开关管与多电平直流变换器的高压电源VH之间的连接关系，将开关管组中与高压电源VH的一端连接的开关管称为第一开关管，将开关管组中与高压电源VH的另一端连接的开关管称为第二开关管。示例性地，第一开关管连接的是高压电源VH的正极端，则第一开关管可以为开关管Q1和开关管Q2。第二开关管连接的是高压电源VH的负极端，第二开关管可以为开关管Q4和开关管Q3。
一个开关管组中的第一开关管和第二开关管的导通和关断状态互补。示例性地，开关管Q1和开关管Q4之间的导通和关断状态互补，则开关管Q1处于导通状态时，开关管Q4处于关断状态。开关管Q1处于关断状态，开关管Q4处于导通状态。如此，可以通过开关管组中的第一开关管和第二开关管中导通的开关管的载波传递电流信号。
由于同一个开关管组内的第一开关管和第二开关管之间的导通和关断状态互补，若开关管组中的第一开关管关断，需控制该开关管组中的第二开关管导通。若开关管组中的第一开关管闭合，需控制该开关组中的第二开关管关断。下文以控制开关管组中的第一开关管的方法进行描述，控制该开关管组中的第二开关管的方法可参照控制第一开关管的方法 的描述进行对应调整。下文以控制开关管组中的第一开关管的方法进行描述，控制该开关管组中的第二开关管的方法可参照控制第一开关管的方法的描述进行对应调整。
本申请以一个飞跨电容进行举例说明，实际上，还可以为2个或多个。例如，图2中未示出的与飞跨电容Cfly串联的另一飞跨电容。或者五电平直流变换器中可存在2个飞跨电容，一个飞跨电容与第一开关管组和第二开关管组并联，其中，第二开关管组包括第一子开关组和第二子开关组，且第一子开关组和第二子开关组与另一个飞跨电容并联。本申请对于电感的大小和数量不做限定，多电平直流变换器还可以包括与电感连接的电容、电阻等。
三电平直流变换器还可以包括图3中的用于控制开关管组的控制器101。该控制器101可以为脉宽调制(pulse width modulation，PWM)器、或者基于PWM技术的电池管理系统(battery management system，BMS)、微控制单元(micro control unit，MCU)、中央处理单元(central processing unit，CPU)、其他通用处理器、数字信号处理器(digital signal processor，DSP)、专用集成电路(application specific integrated circuit，ASIC)、现成可编程门阵列(field-programmable gate array，FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件等。该控制器可以理解为一个芯片或者多个具有通信连接的芯片。控制器可以包括各个开关管分别对应的控制单元，或者可以包括开关管组对应的控制单元，例如，开关管Q1和开关管Q4对应的脉宽调制器，开关管Q2和开关管Q3对应的脉宽调制器等，在此不做限定。
通过PWM技术可以调制开关管Q1、开关管Q2、开关管Q3和开关管Q4的载波，并控制开关管的导通和关断状态，实现功率的实时双向流动。当负载与三电平直流变换器的低压电源VL连接时，三电平直流变换器的输入端为高压电源VH，输出端为低压电源VL，三电平直流变换器的电流从高压电源VH流向低压电源VL。当负载与三电平直流变换器的高压电源VH连接时，三电平直流变换器的输入端为低压电源VL，输出端为高压电源VH，三电平直流变换器的电流从低压电源VL流向高压电源VH。
且还可以通过判断电感L1的电流方向，调整飞跨电容的充放电时间，以实现对飞跨电容的电压进行控制。示例性地，在开关管Q1和开关管Q3导通时，高压电源VH通过开关管Q1、开关管Q3和电感L1作用在低压电源VL上，如果电感L1的电流从高压电源VH流向低压电源VL(电流方向为正)，则飞跨电容Cfly充电，电压升高；如果电感L1的电流从低压电源VL流向高压电压VH(电流方向为负)，则飞跨电容Cfly放电，电压降低；在开关管Q2和开关管Q4导通时，飞跨电容Cfly通过开关管Q2、开关管Q4和电感L1作用在低压电源VL上，如果电感L1的电流方向为正，则飞跨电容Cfly放电，电压降低；如果电感L1的电流方向为负，则飞跨电容Cfly充电，电压升高。
在本申请实施例中，飞跨电容Cfly的电压可简称为飞跨电压，电感的电流可简称为电感电流。若电感电流相对较小，且电感电流为高频三角波在正负之间反复切换，此种情况可称为轻载。反之，电感电流相对较大，且电感电流恒为正，或恒为负，此种情况可称为重载。占空比的差值可以简称为占空比差，移相或相位的差值可以简称为相位差。移相控制的方法是在固定占空比的前提下，对相位进行调整。调整占空比的方法是在固定相位的前提下，对占空比进行调整。如此，可以提高调整的单一性，并保证影响的电压平滑变化。
三电平直流变换器稳态工作时，开关管Q1(开关管Q3)和开关管Q2(开关管Q4)的占空比相等，且移相180°，即开关管Q1载波和开关管Q2载波之间的相位差为180°。因此，可以通过调整开关管Q1和开关管Q2之间的占空比的差值(可简称为占空比差)，来实现三电平直流变换器的稳态运行。例如，在功率由高压电源VH向低压电源VL流动(电流从高压电源VH向低压电源VL流动)时，可以通过增大开关管Q1的占空比、减小开关管Q2的占空比，即增大开关管Q1和开关管Q2之间的占空比差来升高飞跨电压，反之可降低飞跨电压；在功率由低压电源VL向高压电源VH流动(电流从低压电源VL向高压电源VH流动)时，可以通过减小开关管Q1的占空比、增大开关管Q2的占空比，即减小开关管Q1和开关管Q2之间的占空比差来升高飞跨电压，反之可降低飞跨电压。
但是在轻载的情况下，根据瞬时的电流方向控制飞跨电容的电压，对控制芯片有极高的要求，无法适用于实际的工程中。即便将飞跨电容并联的开关管组中的第一开关管(例如，开关管Q1和开关管Q2)或第二开关管(例如，开关管Q3和开关管Q4)的占空比的差值调的很大，也无法将飞跨电容的电压有效地升高或者降低，达不到将飞跨电容的电压稳定在目标值的控制目标。
基于此，本申请提出一种多电平直流变换器，该多电平直流变换器中的控制器用于在飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值的情况下，根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差或两个开关管组中的第一开关管载波之间的相位差。
其中，飞跨电容的采样电压是采集到的实时电压。飞跨电容的参考电压是飞跨电容待调整的目标值。例如，三电平直流变换器的目标值可以为1/2倍的高压电源的电压。电感的电流或称为电感电流，可以为瞬时的电流值或平均值。本申请对于第一阈值不做限定，可以为0等。可以理解，若飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值，则表示飞跨电容的电压还未调整为目标值，可以继续调整并联在飞跨电容一侧的开关管之间的占空比差，或该侧的第一开关管载波之间的相位差，从而对飞跨电容的电压进行控制，可以减小多电平直流变换器的电压应力。若飞跨电容的采样电压和参考电压之间的差值小于或等于第一阈值，则表示飞跨电容的电压已调整为目标值，可以保持当前的工作状态继续工作。如此，可以提高多电平直流变换器运行的稳定性。
本申请对于如何调整相位差和占空比差的方法不做限定，以开关管Q1和开关管Q2进行举例，在确定调整占空比差之后，可以基于前述的根据电流方向的调整方法进行调整。例如，在电流从高压电源流向低压电源的情况下，若飞跨电容Cfly的采样电压小于参考电压，则可以增大两个开关管组中的第一开关管之间的占空比差，即增大开关管Q1的占空比、减小开关管Q2的占空比，来升高飞跨电压；或者在电流从高压电源流向低压电源的情况下，若飞跨电容Cfly的采样电压大于参考电压，则可以减小两个开关管组中的第一开关管之间的占空比差，即减小开关管Q1的占空比、增大开关管Q2的占空比，来降低飞跨电压；或者在电流从低压电源流向高压电源的情况下，若飞跨电容Cfly的采样电压小于参考电压，则可以减小两个开关管组中的第一开关管之间的占空比差，即减小开关管Q1的占空比、增大开关管Q2的占空比，来升高飞跨电压；或者在电流从低压电源流向高压电源的情况下，若飞跨电容Cfly的采样电压大于参考电压，则可以增大两个开关管组中的第一开关管之间 的占空比差，即增大开关管Q1的占空比、减小开关管Q2的占空比，来降低飞跨电压。如此，在决策调整占空比差的情况下，根据电感电流的方向实现了飞跨电容Cfly的电压的调整。
相位差调整飞跨电容Cfly的原理为：增大第一开关管(或第二开关管)载波之间的相位差，使得飞跨电容Cfly的充电时间(面积)大于放电时间(面积)，从而增大飞跨电容Cfly的电压；减小第一开关管(或第二开关管)载波之间的相位差，使得飞跨电容Cfly的充电时间(面积)小于放电时间(面积)，从而减小飞跨电容Cfly的电压。因此，在一种可能的示例中，在根据电感电流的大小确定调整两个开关管组中的第一开关管载波之间的相位差，且飞跨电容Cfly的采样电压小于参考电压的情况下，增大两个开关管组中的第一开关管载波之间的相位差；或者在根据电感电流的大小确定调整两个开关管组中的第一开关管载波之间的相位差，且飞跨电容Cfly的采样电压大于参考电压的情况下，减小两个开关管组中的第一开关管载波之间的相位差。
本申请对于是采用调整相位差的方式还是调整占空比差的方式不做限定，可以先对多电平直流变换器的工况状态进行分析。请参照图4～图9，分别为本申请提出的一种三电平直流变换器的工作模式图。其中，V0为一个周期开始时的飞跨电压Vfly；V1为一个周期中的任一时间的飞跨电压Vfly；V2为一个周期结束时的飞跨电压Vfly；IL为电感电流，在下文中的公式中还以i(t)进行描述；N/A/B/C/M分别为电感电流IL的峰值；T0～T3为一个开关周期内不同阶段的时间点，考虑死区d在不同模式中引起续流回路有所不同，T0～T3的取值有所差异；m/k/n分别为图中所对应的直线的斜率。
下文中的P为开关周期，D1为开关管Q1的占空比，D2为开关管Q2的占空比。三电平直流变换器的占空比D可以理解为理想情况下变换器的稳态占空比，在理想情况下，三电平直流变换器的占空比D等于开关管Q1的占空比D1，且等于开关管Q2的占空比D2。实际由于飞跨电压偏离了目标值，则需要调整开关管Q1和开关管Q2之间的占空比差，或开关管Q1和开关管Q2载波之间的相位差。若占空比D小于0.5，则表示开关管Q1的占空比D1和开关管Q2的占空比D2均小于0.5。若占空比D大于0.5，则表示开关管Q1的占空比D1和开关管Q2的占空比D2均大于0.5。图4～图9分别对应模式一、模式二、模式三、模式四、模式五、模式六，其中：
模式一，占空比D小于0.5，电感电流IL恒为正，即为重载的情况。参照图4，T0＝D1P，T3＝P。
模式二，占空比D小于0.5，电感电流IL恒为负，即为重载的情况。参照图5，T0＝(D1+2d)P，T3＝P。
模式三，占空比D小于0.5，电感电流IL(t)可以为负，也可以为正，即为轻载的情况。参照图6，T0＝(D1+d)P，T3＝P。
模式四，占空比D大于0.5，电感电流IL恒为正，即为重载的情况。参照图7， T0＝(1-D1)P，T3＝P。
模式五，占空比D大于0.5，电感电流IL恒为负，即为轻载的情况。参照图8，T0＝[1-(D1+2d)]P，T3＝P。
模式六，占空比D大于0.5，电感电流IL可以为负，也可以为正，即为轻载的情况。参照图9，T0＝[1-(D1+d)]P，T3＝P。
通过合理建立坐标系，结合图4～图6中电感电流的续流回路，在模式一、模式二、模式三中，可以将死区d合并到占空比D1和占空比D2进行统一分析。结合图7～图9中电感电流的续流回路，在模式四、模式五、模式六中，可以将死区d合并到占空比D1和占空比D2进行统一分析。以下以模式一和模式四为例进行分析，其他模式类推即可。
在一个开关周期内，通过对流过飞跨电容的电流作积分，可得到飞跨电容的电压变化量，如式(1)。
计算式(1)中的公共部分得到式(2)，
其中，m、n、k的取值可参照下面的公式，公式中的L为电感的大小。
若固定开关管Q1(或开关管Q3)和开关管Q2(或开关管Q4)载波之间的相位差为180°，调节占空比D1和占空比D2，可以得到不同的占空比差对飞跨电压的影响。例如，在D<0.5时，将模式一中的时间T0～时间T3带入式(2)中可得式(3)，
在D>0.5时，将模式四中的时间T0～时间T3带入式(2)中可得式(4)，
若固定占空比D1和占空比D2的占空比D(可以为0～1中的任一固定的数值)，调节开 关管Q1(或开关管Q4)和开关管Q2(或开关管Q3)载波之间的相位差为Δθ，可以得到不同的相位差对飞跨电压的影响，即移相控制对飞跨电压的影响。在D<0.5时，将模式一中的时间T0～时间T3带入式(2)中可得式(5)，
在D>0.5时，将模式四中的时间T0～时间T3带入式(2)中可得式(6)，
由式(5)和式(6)可以得到移相控制下飞跨电压在轻重载、正负功率流向下调节方向具有一致性，即：相位差增大，飞跨电压升高；相位差减小，飞跨电压降低。这个关系与死区无关系。
然后，请参照图10～图13，分别为本申请提出的占空比差和相位差与飞跨电压之间的关系图。其中，图10和图11用于描述在固定的相位差和固定的占空比差的情况下，基于不同的负载对于飞跨电压的变化的影响，横轴为电感电流IL，纵轴为飞跨电压的变化量△Vfly。固定占空比差对应的实线反映了对第一开关管调节同样的占空比差，在不同负载下对飞跨电容电压的调节力度。固定相位差对应的虚线反应了对第一开关管调节同样的相位差，在不同负载下对飞跨电容电压的调节力度。图10利用式(3)和式(5)，D＝0.34对D<0.5的应用场景进行举例。图11利用式(4)和式(6)，以D＝0.8对D>0.5的应用场景进行举例。从图10和图11可以看出在轻载(电感电流可以为高频三角波，在正负之间反复切换，且数值较小，可以为图中虚线大于实线，且接近0值的部分)下，飞跨电压的变化值较小。且调整占空比，会使飞跨电压反向变化。随着负载逐渐增大，飞跨电压的变化值逐渐增大，从而可在重载下调整占空比实现飞跨电压的控制。也就是说，调整占空比的方法随着负载逐渐减小，对飞跨电压的控制力度会快速减弱。相比之下，移相控制的控制力度在轻载下相对较强，重载下相对较弱，从而可在轻载下进行移相控制，即调整相位差实现飞跨电压的控制。
图12和图13用于描述在固定的负载的情况下，固定占空比差和固定相位差对于飞跨电压的变化的影响，横轴为占空比D，纵轴为飞跨电压的变化量△Vfly。图12应用为重载下，图13应用于轻载下。从图12和图13可以看出，移相控制的方法随着占空比逐渐增大，对飞跨电压的控制力度快速减弱。但是在轻载下，移相控制的方法相比调整占空比的方法，可以保持较大的调节力度。如此，可以在轻载下，可以采用移相控制的方法实现飞跨电压的控制。重载下可以采用调整占空比的方法实现飞跨电压的控制。
基于此，在一种可能的示例中，控制器具体用于响应于电感电流小于第二阈值，调整两个开关管组中的第一开关管载波之间的相位差。或者控制器具体用于响应于电感电流大于第三阈值，调整两个开关管组中的第一开关管之间的占空比差。或者控制器具体用于响应于电感电流大于或等于第二阈值，且小于或等于第三阈值，根据上一时刻的调整方法调整两个开关管组中的第一开关管之间的占空比差，或两个开关管组中的第一开关管载波之间的相位差。
本申请对于第二阈值和第三阈值的大小不做限定，第二阈值小于第三阈值。可以理解， 若电感的电流小于第二阈值，则表示电感电流较小，可能为轻载的情况，可以在不调整占空比差的前提下，通过移相控制的方法，对两个开关管组中的第一开关管载波之间的相位差进行调整。若电感的电流大于第三阈值，则表示电感电流较大，可能为重载的情况，可以在不调整相位差的前提下，通过调整占空比的方法，对两个开关管组中的第一开关管之间的占空比差进行调整。若电感的电流大于或等于第二阈值，且小于或等于第三阈值，可能为轻载和重载的中间状态，可以采用上一时刻的调整方式进行调整，例如，若上一时刻采用移相控制的方法，则继续采用移相控制的方法；若上一时刻采用调整占空比的方法，则继续采用调整占空比的方法。如此，可以通过以上三种情况实现飞跨电压的控制，使得控制的飞跨电容的电压保持平滑过渡。
在一种可能的示例中，控制器可以包括滞环模块、与滞环模块连接的第一脉宽调制器和第二脉宽调制器。其中，第一脉宽调制器用于调整与飞跨电容连接的一个开关管组中第一开关管(或第二开关管)的相位或占空比，第二脉宽调制器用于调整与飞跨电容连接的另一个开关管组中第一开关管(或第二开关管)的相位或占空比。例如，第一脉宽调制器用于调整开关管Q1或开关管Q4的相位或占空比，第二脉宽调制器用于调整开关管Q2或开关管Q3的相位或占空比。滞环模块可以包括占空比控制器和相位控制器，占空比控制器用于控制第一脉宽调制器和第二脉宽调制器执行占空比控制环路，以实现两个开关管之间的占空比差的调整。相位控制器用于控制第一脉宽调制器和第二脉宽调制器执行相位控制环路，以实现两个开关管载波之间的相位差的调整。
滞环模块用于响应于飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值，根据电感电流的大小，控制第一脉宽调制器和第二脉宽调制器调整两个开关管组中的第一开关管载波之间的相位差或两个开关管组中的第一开关管之间的占空比差。
滞环模块具体用于在根据电感电流的大小确定调整两个开关管组中的第一开关管载波之间的相位差的情况下，若飞跨电容的采样电压小于参考电压，则增大两个开关管组中的第一开关管载波之间的相位差。或者若飞跨电容的采样电压大于参考电压，则减小两个开关管组中的第一开关管载波之间的相位差。
滞环模块具体用于在根据电感电流的大小确定调整两个开关管组中的第一开关管之间的占空比差的情况下，若电流从高压电源流向低压电源，且飞跨电容的采样电压小于参考电压，则增大两个开关管组中的第一开关管之间的占空比差；或者若电流从高压电源流向低压电源，且飞跨电容的采样电压大于参考电压，则减小两个开关管组中的第一开关管之间的占空比差；或者若电流从低压电源流向高压电源，且飞跨电容的采样电压小于参考电压，则减小两个开关管组中的第一开关管之间的占空比差；或者若电流从低压电源流向高压电源，且飞跨电容的采样电压大于参考电压，则增大两个开关管组中的第一开关管之间的占空比差。
滞环模块具体用于响应于电流小于第二阈值，控制第一脉宽调制器和第二脉宽调制器调整两个开关管组中的第一开关管载波之间的相位差；或者响应于电流大于第三阈值，控制第一脉宽调制器和第二脉宽调制器调整两个开关管组中的第一开关管之间的占空比差；或者响应于电流大于或等于第二阈值，且小于或等于第三阈值，根据上一时刻的调整方法控制第一脉宽调制器和第二脉宽调制器调整两个开关管组中的第一开关管载波之间的相位 差或两个开关管组中的第一开关管之间的占空比差。
以第一开关管为开关管Q1和开关管Q2进行举例说明，请参照图14，图14为本申请提供一种控制器调整飞跨电容的电压的流程示意图。如图14所示，滞环模块可以先确定飞跨电容的采样电压Vfly_ad和飞跨电容的参考电压Vfly_ref之间的差值的绝对值是否大于第一阈值。若是，且电感电流的平均值iLAVG小于第二阈值，可以在控制占空比不变(占空比控制环的输出限幅线性变化为零)的前提下，控制相位控制器对应的移相控制环工作，以使第一脉宽调制器根据电感电流的方向将当前的占空比控制环的输出结果作用于稳态占空比上。再由第二脉宽调制器将移相控制环的输出结果相加于第二脉宽调制器对应的开关管的载波上，使得第一脉宽调制器对应的开关管Q1和第二脉宽调制器对应的开关管Q2载波之间的相位差在180°附近动态调节。当iLAVG大于第三阈值，可以在控制相位差不变的前提下，控制占空比控制器对应的占空比控制环工作，以使第一脉宽调制器和第二脉宽调制器，根据电感电流的方向将当前的移相控制环的输出结果作用于第二脉宽调制器对应的载波上，使得开关管Q1和开关管Q2之间的占空比差在0附近动态调节。当iLAVG处于第二阈值和第三阈值之间，保持前一时刻的调整方式控制相位控制器对应的移相控制环工作，以使第一脉宽调制器和第二脉宽调制器调整开关管Q1和开关管Q2载波之间的相位比差，或控制占空比控制器对应的占空比控制环工作，以使第一脉宽调制器和第二脉宽调制器调整开关管Q1和开关管Q2之间的占空比差。
请参照图15，图15为本申请提供的一种飞跨电容的电压控制方法的流程图。该飞跨电容可应用于如图3所示的多电平直流变换器中，该多电平直流变换器包括至少一个飞跨电容、与飞跨电容连接的两个开关管组、与各个开关管组和多电平直流变换器的低压电压的正极端连接的电感，以及用于控制开关管组的控制器。其中，各个开关管组均包括导通和关断状态互补的第一开关管和第二开关管。如图15所示，该电压控制方法可以包括步骤S101，其中：
S101：在飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值，控制器根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差或两个开关管组中的第一开关管载波之间的相位差。
可以理解，若飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值，则表示飞跨电容的电压还未调整为目标值，可以继续调整并联在飞跨电容一侧的开关管之间的相位差，或该侧的开关管之间的占空比差，从而对飞跨电容的电压进行控制，提高了多电平直流变换器运行的稳定性。
在一种可能的示例中，根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差，或两个开关管组中的第一开关管载波之间的相位差的方法，可以包括以下步骤：在根据电感电流的大小确定调整两个开关管组中的第一开关管载波之间的相位差，且飞跨电容的采样电压小于参考电压的情况下，增大两个开关管组中的第一开关管载波之间的相位差；或者在根据电感电流的大小确定调整两个开关管组中的第一开关管载波之间的相位差，且飞跨电容的采样电压大于参考电压的情况下，减小两个开关管组中的第一开关管载波之间的相位差。如此，通过增大两个开关管组中第一开关管载波之间的相位差升高 飞跨电容的电压。通过减小两个开关管组中第一开关管载波之间的相位差减小飞跨电容的电压。
在一种可能的示例中，根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差，或两个开关管组中的第一开关管载波之间的相位差的方法，可以包括以下步骤：在根据电感电流的大小确定调整两个开关管组中的第一开关管之间的占空比差的情况下，若电流从高压电源流向低压电源，且飞跨电容的采样电压小于参考电压，则增大两个开关管组中的第一开关管之间的占空比差；或者若电流从高压电源流向低压电源，且飞跨电容的采样电压大于参考电压，则减小两个开关管组中的第一开关管之间的占空比差；或者若电流从低压电源流向高压电源，且飞跨电容的采样电压小于参考电压，则减小两个开关管组中的第一开关管之间的占空比差；或者若电流从低压电源流向高压电源，且飞跨电容的采样电压大于参考电压，则增大两个开关管组中的第一开关管之间的占空比差。如此，在决策调整占空比差的情况下，根据电感电流的方向实现了飞跨电容的电压的调整。
在一种可能的示例中，根据电感电流的大小，调整两个开关管组中的第一开关管之间的占空比差或两个开关管组中的第一开关管载波之间的相位差的方法，可以包括以下步骤：在电感电流小于第二阈值的情况下，调整两个开关管组中的第一开关管载波之间的相位差；或者在电感电流大于第三阈值的情况下，调整两个开关管组中的第一开关管之间的占空比差；或者在电感电流大于或等于第二阈值，且小于或等于第三阈值的情况下，根据上一时刻的调整方法调整两个开关管组中的第一开关管之间的占空比差或两个开关管组中的第一开关管载波之间的相位差。如此，可以通过以上三种情况实现飞跨电压的控制，使得控制的飞跨电容的电压保持平滑过渡。
本申请实施例还公开一种控制装置。该控制装置包括控制器和存储器；其中，存储器用于存储指令，控制器用于调用该存储器中存储的指令，执行上述任一方面中的方法。
本领域普通技术人员可以理解：实现上述方法实施例的全部或部分步骤可以通过程序指令相关的硬件来完成，前述的程序可以存储于一计算机可读取存储介质中，该程序在执行时，执行包括上述方法实施例的步骤；而前述的存储介质包括：移动存储设备、只读存储器(read-only memory，ROM)、随机存取存储器(random access memory，RAM)、磁碟或者光盘等各种可以存储程序代码的介质。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应以所述权利要求的保护范围为准。

Claims (10)

  1. 一种多电平直流变换器，其特征在于，所述多电平直流变换器包括至少一个飞跨电容、与所述飞跨电容连接的两个开关管组、与各个所述开关管组和所述多电平直流变换器的低压电源的正极端连接的电感，以及用于控制所述开关管组的控制器；其中，所述开关管组均包括导通和关断状态互补的第一开关管和第二开关管，所述第一开关管连接所述多电平直流变换器的高压电源的一端，所述第二开关管连接所述多电平直流变换器的高压电源的另一端；
    所述控制器，用于在所述飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值的情况下，根据所述电感电流的大小，调整所述两个开关管组中的第一开关管之间的占空比差或所述两个开关管组中的第一开关管载波之间的相位差。
  2. 根据权利要求1所述的多电平直流变换器，其特征在于，所述控制器具体用于在根据所述电感电流的大小确定调整所述两个开关管组中的第一开关管载波之间的相位差，且所述飞跨电容的采样电压小于所述参考电压的情况下，增大所述两个开关管组中的第一开关管载波之间的相位差。
  3. 根据权利要求1所述的多电平直流变换器，其特征在于，所述控制器具体用于在根据所述电感电流的大小确定调整所述两个开关管组中的第一开关管载波之间的相位差，且所述飞跨电容的采样电压大于所述参考电压的情况下，减小所述两个开关管组中的第一开关管载波之间的相位差。
  4. 根据权利要求1-3中任一项所述的多电平直流变换器，其特征在于，所述控制器，具体用于在所述电感电流小于第二阈值的情况下，调整所述两个开关管组中的第一开关管载波之间的相位差。
  5. 根据权利要求1所述的多电平直流变换器，其特征在于，所述控制器，具体用于在所述电感电流大于第三阈值的情况下，调整所述两个开关管组中的第一开关管之间的占空比差。
  6. 根据权利要求1-3中任一项所述的多电平直流变换器，其特征在于，所述控制器，具体用于在所述电感电流大于或等于第二阈值，且小于或等于第三阈值的情况下，根据上一时刻的调整方法调整所述两个开关管组中的第一开关管之间的占空比差，或所述两个开关管组中的第一开关管载波之间的相位差。
  7. 一种飞跨电容的电压控制方法，其特征在于，所述飞跨电容应用于多电平直流变换器中，所述多电平直流变换器还包括两个开关管组、电感和控制器，各个所述开关管组均包括导通和关断状态互补的第一开关管和第二开关管；所述电压控制方法包括：
    在所述飞跨电容的采样电压和参考电压之间的差值的绝对值大于第一阈值的情况下，所述控制器根据所述电感电流的大小，调整所述两个开关管组中的第一开关管之间的占空比差或所述两个开关管组中的第一开关管载波之间的相位差。
  8. 根据权利要求7所述的电压控制方法，其特征在于，所述控制器根据所述电感电流的大小，调整所述两个开关管组中的第一开关管之间的占空比差或所述两个开关管组中的第一开关管载波之间的相位差，包括：
    在根据所述电感电流的大小确定调整所述两个开关管组中的第一开关管载波之间的相位差，且所述飞跨电容的采样电压小于所述参考电压的情况下，所述控制器增大所述两个开关管组中的第一开关管载波之间的相位差；或者
    在根据所述电感电流的大小确定调整所述两个开关管组中的第一开关管载波之间的相位差，且所述飞跨电容的采样电压大于所述参考电压的情况下，所述控制器减小所述两个开关管组中的第一开关管载波之间的相位差。
  9. 根据权利要求7或8所述的电压控制方法，其特征在于，所述控制器根据所述电感电流的大小，调整所述两个开关管组中的第一开关管之间的占空比差或所述两个开关管组中的第一开关管载波之间的相位差，包括：
    在所述电感电流小于第二阈值的情况下，所述控制器调整所述两个开关管组中的第一开关管载波之间的相位差；或者
    在所述电感电流大于第三阈值的情况下，所述控制器调整所述两个开关管组中的第一开关管之间的占空比差；或者
    在所述电感电流大于或等于第二阈值，且小于或等于第三阈值的情况下，所述控制器根据上一时刻的调整方法调整所述两个开关管组中的第一开关管之间的占空比差或所述两个开关管组中的第一开关管载波之间的相位差。
  10. 一种控制装置，其特征在于，所述控制装置包括控制器和存储器；其中，所述存储器用于存储指令，所述控制器用于调用所述存储器中存储的指令，执行如权利要求7-9中任一项所述的电压控制方法。
PCT/CN2023/098923 2022-06-23 2023-06-07 多电平直流变换器和飞跨电容的电压控制方法、控制装置 WO2023246512A1 (zh)

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