WO2022051892A1 - 一种三电平逆变器、控制方法及*** - Google Patents

一种三电平逆变器、控制方法及*** Download PDF

Info

Publication number
WO2022051892A1
WO2022051892A1 PCT/CN2020/113953 CN2020113953W WO2022051892A1 WO 2022051892 A1 WO2022051892 A1 WO 2022051892A1 CN 2020113953 W CN2020113953 W CN 2020113953W WO 2022051892 A1 WO2022051892 A1 WO 2022051892A1
Authority
WO
WIPO (PCT)
Prior art keywords
current
command
grid
level inverter
equalization
Prior art date
Application number
PCT/CN2020/113953
Other languages
English (en)
French (fr)
Inventor
徐飞
于心宇
辛凯
徐志武
李琳
郭海滨
Original Assignee
华为数字能源技术有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 华为数字能源技术有限公司 filed Critical 华为数字能源技术有限公司
Priority to PCT/CN2020/113953 priority Critical patent/WO2022051892A1/zh
Priority to CN202311192543.3A priority patent/CN117220532A/zh
Priority to EP20952681.3A priority patent/EP4195489A4/en
Priority to CN202080024643.3A priority patent/CN114982121B/zh
Publication of WO2022051892A1 publication Critical patent/WO2022051892A1/zh
Priority to US18/179,098 priority patent/US20230238896A1/en

Links

Images

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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/4833—Capacitor voltage balancing
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/487—Neutral point clamped inverters
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal 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
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • 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
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0025—Arrangements for modifying reference values, feedback values or error values in the control loop of a converter

Definitions

  • the present application relates to the technical field of power electronics, and in particular, to a three-level inverter, a control method and a system.
  • Photovoltaic power generation is a technology that uses the photovoltaic effect of the semiconductor interface to convert light energy into electrical energy, and has been developing rapidly.
  • the photovoltaic inverter is the core component in the photovoltaic power generation system, which is used to convert the direct current generated by photovoltaic modules into alternating current.
  • three-level inverter As a kind of photovoltaic inverter, three-level inverter has three-level bridge arm voltage, which is more than two-level inverter. It is widely used because it can effectively reduce the volume of passive devices such as filter inductors. application.
  • the three-level inverter has a bus midpoint, and the balance of the bus midpoint potential involves many indicators such as the withstand voltage of the inverter power device, the harmonics of the grid-connected current, and so on. The balanced control of the midpoint potential is crucial.
  • the photovoltaic power generation system When the photovoltaic power generation system is applied to the grid-connected scenario, the photovoltaic power generation system is connected to the power grid, and there will be a large disturbance of voltage background harmonics in the power grid.
  • the harmonics of the voltage background will cause the grid-connected current to contain current harmonics of the same frequency.
  • the voltages of the positive and negative DC busbars are unbalanced, causing the offset of the midpoint of the DC busbars, threatening the normal operation of the inverter.
  • the present application provides a three-level inverter, a control method and a system, wherein the voltages of the positive and negative DC buses of the three-level inverter can be balanced.
  • the present application provides a three-level inverter, the three-level inverter includes a first bus capacitor, a second bus capacitor, a power conversion circuit and a controller.
  • the first end of the first bus capacitor is connected to the positive DC bus and the first input end of the power conversion circuit, and the second end of the first bus capacitor is connected to the negative DC bus and the second input end of the power conversion circuit through the second bus capacitor , the second end of the first bus capacitor is also connected to the third input end of the power conversion circuit;
  • the power conversion circuit is used to convert the direct current into three-phase alternating current and output;
  • the controller is used to utilize the difference between the absolute values of the positive and negative DC bus voltages value, and the even-order harmonic current in the grid-connected current to determine the equalization command, which is used to make the three-level inverter generate a current signal that equalizes the positive and negative DC bus voltages.
  • the technical solution provided by the present application fully considers the influence of the even-order harmonic current in the grid-connected current on the midpoint potential of the bus bar of the three-level inverter.
  • the controller of the three-level inverter uses the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter to characterize the deviation of the current bus mid-point potential, and combines the even current in the grid-connected current.
  • the sub-harmonic current determines the balance command, and the grid-connected current is adjusted by using the current balance command.
  • the current signal generated according to the current balancing command and the even-order harmonic current in the grid-connected current can be superimposed to weaken the even-order harmonic current, so the positive and negative bus voltages of the three-level inverter can be balanced.
  • the harmonics of the grid-connected current are suppressed, and the adaptability of the three-level inverter to the power grid is improved, so that the three-level inverter takes into account the balance control of the busbar and the harmonics of the grid-connected current in the harsh grid environment. wave suppression.
  • the controller uses the difference to determine the harmonic amplitude coefficient, and then determines the type of the even-order harmonic current in the grid-connected current, and the even-order of each type.
  • the weight coefficient corresponding to the harmonic current the weight coefficient is positively related to the influence degree of the even-order harmonics on the grid-connected current, and then use the harmonic amplitude coefficient, the type and weight coefficient corresponding to each even-order harmonic current to determine the equalization command .
  • the equalization command combines the type and weight coefficient corresponding to each even-order harmonic current, and can suppress the even-order harmonic current.
  • the controller is specifically configured to obtain the equalization command component corresponding to each even-order harmonic current, and the equalization command component is the amplitude coefficient and the weight of the even-order harmonic current.
  • the product of the coefficient and the type; the equalization command components corresponding to each even harmonic current are superimposed to obtain the equalization command.
  • the controller is specifically configured to superimpose the equalization command and the grid-connected current to obtain the grid-connected current command; use the grid-connected current command to obtain the first equalization voltage command; use the first equalization command to obtain the first equalization voltage command;
  • the voltage command adjusts the drive command of the three-level inverter, and the obtained first equalized voltage command is superimposed with the original control signal of the three-level inverter to generate a drive signal for driving the three-level inverter, So that the output current of the three-level inverter generates a current signal for reducing the even-order harmonic current.
  • the controller superimposes the balancing command and the grid-connected current to obtain the grid-connected current command; uses the grid-connected current command to obtain the first balancing voltage command; uses the difference to obtain the second balancing command voltage command; using the first balanced voltage command and the second balanced voltage command to adjust the driving command of the three-level inverter, so that the output current of the three-level inverter generates a voltage for reducing the even-order harmonic current. current signal.
  • the second equalizing voltage command is the common mode voltage of the three-level inverter.
  • the first balanced voltage command and the second balanced voltage command are superimposed to generate the balanced voltage composite control command, and the obtained control signal and the original control signal of the three-level inverter are superimposed to generate a control signal for driving the three-level inverter. driver signal.
  • the ratio of the weight coefficients corresponding to each even-order harmonic current is the ratio of the amplitudes of each even-order harmonic current. That is, the weight coefficient is positively correlated with the amplitude. The higher the amplitude, the greater the corresponding even harmonic current and the greater the influence on the grid-connected current.
  • the controller uses the difference value when the even-order harmonic current in the grid-connected current is less than the preset current threshold value, and/or when the difference value is less than the preset voltage threshold value. Obtain the equalization instruction.
  • the even-order harmonic current in the grid-connected current is less than the preset current threshold, it indicates that the even-order harmonic current has little influence on the potential of the midpoint of the busbar and can be ignored; when the absolute value of the positive and negative DC busbar voltages When the difference between the values is smaller than the preset voltage threshold, it indicates that the potential at the midpoint of the bus is less affected by the even-order harmonic current at this time. Therefore, when at least one of the above two conditions is satisfied, the condition of the power grid at this time is better, and the influence of the even-order harmonic current in the grid-connected current is small. Therefore, the difference value can be used to obtain the equalization command. At this time, the equalization command is the equalization control quantity of the three-phase common mode voltage bus.
  • the controller is specifically configured to use the equalization command to adjust the drive command of the three-level inverter.
  • the phase of the current signal and the even-order harmonic current is opposite, so that the even-order harmonic current in the grid-connected current is minimized while equalizing the bus potential.
  • the present application also provides a control method for an inverter, the method comprising: using the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter, and the difference in the grid-connected current
  • the sub-harmonic current determines the equalization command, which is used to make the three-level inverter generate a current signal that equalizes the positive and negative DC bus voltages; the equalization command is used to adjust the grid-connected current.
  • the method uses the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter to characterize the deviation of the current bus midpoint potential, and determines the equalization command in combination with the even-order harmonic current in the grid-connected current.
  • the grid-connected current is adjusted by using the current balance command, so that a current signal for reducing the even-order harmonic current is generated in the grid-connected current. That is, the current signal generated according to the current balance command and the even-order harmonic current in the grid-connected current can weaken the even-order harmonic current after superposition, thus ensuring the balance of the positive and negative bus voltages of the three-level inverter.
  • this method suppresses the harmonics of the grid-connected current, it also improves the adaptability of the three-level inverter to the power grid, and reduces the three-level inverter caused by the unbalanced bus potential when the power grid environment is harsh. The probability of protection shutdown,
  • the determination is determined by using the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter and the even-order harmonic current in the grid-connected current.
  • the equalization command includes: using the difference to determine the harmonic amplitude coefficient; determining the type of the even-order harmonic current in the grid-connected current, and the weighting coefficient corresponding to the even-order harmonic current of each type, and the weighting coefficient is the same as that of all harmonic currents.
  • the influence degree of the even harmonics on the grid-connected current is positively correlated; the harmonic amplitude coefficient, the type and weight coefficient corresponding to each even harmonic current are used to determine the equalization command.
  • the harmonic amplitude coefficient, the type and weight coefficient corresponding to each even-order harmonic current are used to determine the equalization command, which specifically includes: obtaining each even-order harmonic current
  • the corresponding equalization command component is the product of the amplitude coefficient, the weight coefficient of the even harmonic current and the type; the equalization command components corresponding to each even harmonic current are superimposed to obtain the equalization command.
  • using the balancing command to adjust the grid-connected current specifically includes: superimposing the balancing command and the grid-connected current to obtain the grid-connected current command; using the grid-connected current command to obtain the first balancing voltage The command; the first balanced voltage command is used to adjust the driving command of the three-level inverter, so that a current signal for reducing the even-order harmonic current is generated in the output current of the three-level inverter.
  • using the balancing command to adjust the grid-connected current specifically includes: superimposing the balancing command and the grid-connected current to obtain the grid-connected current command; using the grid-connected current command to obtain the first balancing voltage instruction; use the difference to obtain the second equalization voltage instruction, the second equalization voltage instruction is the common mode voltage of the three-level inverter; use the first equalization voltage instruction and the second equalization voltage instruction to adjust the three-level inverter
  • the driving command is used to generate a current signal for reducing the even-order harmonic current in the output current of the three-level inverter.
  • the ratio of the weight coefficients corresponding to each even-order harmonic current is the ratio of the amplitude of each of the even-order harmonic currents.
  • the balance command is determined by using the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter and the even-order harmonic current in the grid-connected current. , which specifically includes: when the even-order harmonic current in the grid-connected current is less than a preset current threshold, and/or when the difference is less than a preset voltage threshold, using the difference to obtain an equalization command.
  • using the equalization command to adjust the grid-connected current specifically includes: using the equalization command to adjust the drive command of the three-level inverter.
  • the phase of the current signal is opposite to that of the even harmonic current.
  • the present application also provides an inverter control device, the device includes: a determination unit and an adjustment unit.
  • the determining unit is used for determining an equalization command by using the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter and the even-order harmonic current in the grid-connected current, and the equalization command is used to make the three-level inverter
  • the inverter produces a current signal that balances the positive and negative DC bus voltages.
  • the adjustment unit is used to adjust the grid-connected current using the equalization command.
  • the determination unit specifically includes: a first coefficient determination subunit, a second coefficient determination subunit, and a first instruction determination subunit.
  • the first coefficient determination sub-unit is used for determining the harmonic amplitude coefficient using the difference value.
  • the second coefficient determination subunit is used to determine the type of the even-order harmonic current in the grid-connected current, and the weighting coefficient corresponding to the even-order harmonic current of each type. The degree of influence is positively correlated.
  • the first instruction determination subunit is configured to determine the equalization instruction by using the harmonic amplitude coefficient, the type and weight coefficient corresponding to each even-order harmonic current.
  • the first command determination subunit is specifically used to: obtain the equalization command component corresponding to each even-order harmonic current, and the equalization command component is the amplitude coefficient, the even-order harmonic current The product of the weight coefficient of the harmonic current and the type order; the equalization command components corresponding to each even-order harmonic current are superimposed to obtain the equalization command.
  • the adjustment unit is specifically configured to: superimpose the equalization command and the grid-connected current to obtain the grid-connected current command; use the grid-connected current command to obtain the first equalization voltage command; use the first The equalizing voltage command adjusts the driving command of the three-level inverter, so that a current signal for reducing the even-order harmonic current is generated in the output current of the three-level inverter.
  • the adjustment unit is specifically configured to: superimpose the equalization command and the grid-connected current to obtain the grid-connected current command; use the grid-connected current command to obtain the first equalization voltage command; use the difference value Acquiring the second balanced voltage command; using the first balanced voltage command and the second balanced voltage command to adjust the driving command of the three-level inverter, so that the output current of the three-level inverter is used to reduce even-order harmonics. Current signal of current.
  • the ratio of the weighting coefficients corresponding to each even-order harmonic current is the ratio of the amplitudes of each even-order harmonic current.
  • the determining unit is specifically configured to, when the even-order harmonic current in the grid-connected current is less than the preset current threshold, and/or when the difference value is less than the preset voltage threshold, Use the difference to obtain equalization commands.
  • the adjusting unit is specifically the same as: adjusting the driving instruction of the three-level inverter by using an equalization instruction.
  • the phase of the current signal is opposite to that of the even-order harmonic current.
  • the present application further provides a photovoltaic power generation system
  • the photovoltaic power generation system includes the three-level inverter provided in any of the above implementation manners, and further includes a photovoltaic unit.
  • the photovoltaic unit includes a plurality of photovoltaic components, and the output end of the photovoltaic unit is connected to the input end of the three-level inverter. Photovoltaic units are used to convert light energy into direct current and then transmit it to a three-level inverter.
  • the present application further provides a computer-readable storage medium, where a computing program is stored on the storage medium, and when the computer program is executed, the control method provided by any of the above implementation manners is implemented.
  • Figure 1 is a schematic diagram of a photovoltaic system
  • FIG. 2 is a flowchart of a control method of a three-level inverter provided by an embodiment of the present application
  • FIG. 3 is a flowchart of another method for controlling a three-level inverter provided by an embodiment of the present application.
  • FIG. 4 is a control block diagram provided by an embodiment of the present application.
  • FIG. 5 is a flowchart of a method for determining an equalization command provided by an embodiment of the present application
  • FIG. 6 is a waveform diagram provided by an embodiment of the present application when the control method of the present application is not adopted;
  • FIG. 7 is a waveform diagram when the control method of the present application is adopted provided by an embodiment of the present application.
  • FIG. 8 is a waveform diagram of the grid-connected current corresponding to FIG. 6 provided by an embodiment of the application.
  • FIG. 9 is a waveform diagram of the grid-connected current corresponding to FIG. 7 provided by an embodiment of the present application.
  • FIG. 10 is a flowchart of another method for controlling a three-level inverter provided by an embodiment of the application.
  • FIG. 11 is another control block diagram provided by this embodiment of the application.
  • FIG. 12 is a flowchart of still another method for controlling a three-level inverter provided by an embodiment of the application.
  • FIG. 13 is a schematic diagram of a control device of a three-level inverter provided by an embodiment of the application.
  • FIG. 14 is a schematic diagram of another control device of a three-level inverter provided by an embodiment of the application.
  • FIG. 15 is a schematic diagram of a three-level inverter provided by an embodiment of the application.
  • 16 is a schematic diagram of a power conversion circuit provided by an embodiment of the application.
  • FIG. 17 is a schematic diagram of a photovoltaic power generation system provided by an embodiment of the present application.
  • FIG. 1 is a schematic diagram of a photovoltaic system.
  • the illustrated photovoltaic system includes photovoltaic units 10 and a three-level inverter 20 , and the photovoltaic system is connected to a grid 30 .
  • the photovoltaic unit 10 includes a plurality of photovoltaic (PV) components, which are connected in series or in parallel. For example, a plurality of photovoltaic components can be connected in series to form a photovoltaic string, and then a plurality of photovoltaic strings can be connected in series to form the photovoltaic unit 10 .
  • PV photovoltaic
  • the three-level inverter 20 is used to convert the direct current generated by the photovoltaic module 10 into alternating current and then transmit it to the grid.
  • the output current of the photovoltaic system is represented by ig, and the voltage of the grid is represented by Ug.
  • the three-level inverter 20 includes: bus capacitors C1 and C2 and a power conversion circuit 201 .
  • the midpoint of the positive and negative DC busbars is represented by N.
  • the balance of the potential at the midpoint N involves many indicators such as the withstand voltage of the power device of the three-level inverter, the harmonics of the grid-connected current, etc. Therefore, the three-level inverter
  • the balanced control of the midpoint potential of the device is very important.
  • the present application provides a three-level inverter, a control method and a system, which fully consider the effect of the even harmonic current in the grid-connected current on the potential of the bus midpoint of the three-level inverter. influence.
  • the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter and the even-order harmonic current in the grid-connected current is used to determine the balance command, and the current balance command is used to adjust the grid-connected current, so that the parallel A current signal for reducing the even harmonic current is generated in the grid current, which reduces the influence of the grid-connected current on the three-level inverter, thus ensuring the balance of the positive and negative bus voltages of the three-level inverter.
  • the harmonics of the grid-connected current are suppressed, so the adaptability of the three-level inverter to the power grid is also improved, and the protection shutdown of the three-level inverter caused by the unbalanced bus potential when the power grid environment is harsh is reduced. The probability.
  • connection should be understood in a broad sense.
  • connection may be a fixed connection, a detachable connection, or an integral body; it may be a direct connection, or a Indirect connections can be made through an intermediary.
  • the inventor found that for a power grid with poor conditions, since the voltage U g of the power grid contains a large even-order harmonic current, the grid-connected current ig of the three-level inverter 20 also contains a certain amount of the same harmonic current. Frequency harmonic current, and even harmonic current will cause the energy transfer between the positive and negative DC busbars of the photovoltaic system, which will lead to the voltage imbalance of the positive and negative DC busbars.
  • Table 1 The specific energy transfer situation can be seen in Table 1.
  • Table 1 Correspondence table of DC bus energy transfer due to harmonic currents
  • the frequency of the even harmonic current is an even multiple of the frequency of the grid-connected current, such as 2, 4, and 8 times.
  • the current mid-point potential balance control strategy has an upper limit of control ability.
  • the energy transfer of the positive and negative DC buses caused by the even harmonic current is serious, the current strategy is not enough to suppress the problem, which may eventually lead to the neutral point of the DC bus.
  • the potential offset threatens the normal and reliable operation of the three-level inverter. In severe cases, the three-level inverter will be shut down in batches for protection, and the phenomenon of disconnection will occur.
  • the embodiments of the present application provide a control method for a three-level inverter, which will be described in detail below with reference to the accompanying drawings.
  • FIG. 2 is a flowchart of a control method for a three-level inverter provided by an embodiment of the present application.
  • the method provided by the embodiment of the present application can be implemented by a controller of a three-level inverter, and the method includes the following steps:
  • S101 Determine the balance command by using the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter and the even-order harmonic current in the grid-connected current, and the balance command is used to make the three-level inverter generate A current signal that equalizes the positive and negative DC bus voltages.
  • the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter characterizes the offset degree of the midpoint potential of the DC bus at this time, and also characterizes the effect of the even harmonic current in the current grid-connected current on the bus.
  • the effect of the potential at the midpoint of the DC line is illustrated by the following example:
  • the grid-connected current can also be sampled in real time, and the harmonic information of the grid-connected current can be analyzed to obtain even-order harmonic current information in the grid-connected current.
  • the amplitude information, type information and so on of the even harmonic current are obtained.
  • the type of the even harmonic current represents the multiple relationship between the frequency of the even harmonic current and the frequency of the grid-connected current. The larger the type, the larger the frequency of the harmonic current.
  • the equalization command is determined based on the difference and even harmonic currents in the grid-connected current.
  • the function of the equalization command is to make the three-level inverter generate a current signal for reducing the even-order harmonic current in the grid-connected current, that is, the generated current signal weakens the even-order harmonic current.
  • the three-level inverter The effect of the positive and negative DC bus midpoint voltage.
  • the working state of the three-level inverter is controlled by the equalization command obtained in S101, so that the positive and negative DC busbars of the three-level inverter can achieve voltage equalization.
  • the output current of the three-level inverter that is, the grid-connected current is adjusted.
  • the control method provided by the present application fully considers the influence of the even-order harmonic current in the grid-connected current on the midpoint potential of the bus bar of the three-level inverter.
  • the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter is used to characterize the deviation of the current DC bus mid-point potential.
  • the current balance command adjusts the grid-connected current, so that a current signal for reducing the even-order harmonic current is generated in the grid-connected current. That is, the current signal generated according to the current balance command and the even-order harmonic current in the grid-connected current can weaken the even-order harmonic current after superposition, thus ensuring the balance of the positive and negative bus voltages of the three-level inverter.
  • this method suppresses the harmonics of the grid-connected current, it also improves the adaptability of the three-level inverter to the power grid, and reduces the three-level inverter caused by the unbalanced bus potential when the power grid environment is harsh.
  • the probability of shutdown enhances the friendliness of grid connection, from adapting to the grid to supporting the grid.
  • Embodiment 2 is a diagrammatic representation of Embodiment 1:
  • FIG. 3 is a flowchart of another method for controlling a three-level inverter provided by an embodiment of the present application.
  • control block diagram shown in FIG. 4 may also be referred to.
  • S201 Determine the harmonic amplitude coefficient by using the difference between the absolute values of the positive and negative DC bus voltages.
  • the voltages of the positive and negative DC buses are collected in real time, and the difference ⁇ U between the absolute values of the two is obtained.
  • the deviation ⁇ U can be generated by the proportional integral controller (PI controller) 401 to generate harmonic Amplitude coefficient Im.
  • the harmonic amplitude coefficient represents the amplitude of the even-order harmonic current in the grid-connected current at this time.
  • S202 Determine the type of the even-order harmonic current in the grid-connected current, and the weighting coefficient corresponding to the even-order harmonic current of each type, and the weighting coefficient is positively related to the influence degree of the even-order harmonic current on the grid-connected current .
  • the detection unit 402 implements the sampling of the grid-connected current ig, and the processing unit 403 analyzes the sampling information of the grid-connected current, and then obtains the type of the even-order harmonic current in the grid-connected current and the weight coefficient corresponding to the even-order harmonic current of each type. .
  • the harmonic type selection unit determines the current type of each even harmonic according to the distribution of each harmonic in the grid-connected current:
  • w is the angular frequency of the fundamental wave
  • ⁇ n is the starting phase angle of the harmonic type
  • n 2 ⁇ i, i ⁇ [-N,N], where N is a positive integer.
  • the harmonic weight distribution unit determines the weight coefficient k n corresponding to the even-order harmonic current of each type, and the weight coefficient is positively related to the influence degree of the even-order harmonic on the grid-connected current. Specific restrictions.
  • the ratio of the weighting coefficient corresponding to each even-order harmonic current is the ratio of the amplitude of each even-order harmonic current, that is, the weighting coefficient is positively correlated with the amplitude, and the higher the amplitude, the higher the corresponding even-order harmonic current.
  • the greater the harmonic current the greater the influence on the grid-connected current. Therefore, the weight coefficient of the second harmonic current is the largest.
  • the type of the even harmonic current to be considered can be determined according to the specific requirements for the potential of the positive and negative DC busbars when the three-level inverter is working normally. , and for the even-order harmonic currents of particularly high order, the influence on the grid-connected current can be neglected due to its extremely low weight coefficient.
  • S203 Determine the equalization command by using the harmonic amplitude coefficient, the type and weight coefficient corresponding to each even-order harmonic current.
  • the equalization command combines the type and weight coefficient corresponding to each even-order harmonic current, and is used to generate a current signal for reducing the even-order harmonic current in the output current of the three-level inverter, that is, the equalization command is used to suppress Even harmonic currents.
  • FIG. 5 is a flowchart of a method for determining an equalization command provided by an embodiment of the present application.
  • S203a Obtain the equalization command component corresponding to each even harmonic current, where the equalization command component is the product of the amplitude coefficient, the weight coefficient of the even harmonic current and the type.
  • the equalization command component is ij points (t), which is shown in the following formula:
  • S203b Superimpose the equalization command components corresponding to each even-order harmonic current to obtain an equalization command.
  • the equalization command is i j (t), which is as follows:
  • even-order harmonic currents whose weight coefficient is smaller than the preset weight threshold value may be ignored, and the present application does not specifically limit the determination method and specific value of the preset weight threshold value.
  • the grid-connected current command i ref is as follows:
  • i ref i g + i j (t) (4)
  • the grid-connected current command i ref generates the first equalization voltage command U ref_h after passing through the grid-connected current loop 404 .
  • the loop, the detection and control principle of the loop is a relatively mature prior art, and details are not described here in this embodiment of the present application.
  • S206 Adjust the driving command of the three-level inverter by using the first balanced voltage command, so that a current signal for reducing the even-order harmonic current is generated in the output current of the three-level inverter.
  • the obtained U ref_h is superimposed with the original control signal of the three-level inverter to generate a driving signal for driving the three-level inverter.
  • the three-level inverter includes a controllable switch tube, and the embodiment of the present application does not specifically limit the type of the controllable switch tube, for example, it may be an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT), a metal oxide semiconductor Field effect transistor (Metal Oxide Semiconductor Filed Effect Transistor, MOSFET, hereinafter referred to as MOS tube), SiC MOSFET (Silicon Carbide Metal Oxide Semiconductor, silicon carbide field effect transistor) and the like.
  • IGBT Insulated Gate Bipolar Transistor
  • MOSFET Metal Oxide Semiconductor Filed Effect Transistor
  • SiC MOSFET Silicon Carbide Metal Oxide Semiconductor, silicon carbide field effect transistor
  • the controller adjusts the working state of the controllable switch tube by adjusting the PWM (Pulse Width Modulation) signal acting on the controllable switch tube, so that the three-level inverter A current signal for reducing even harmonic currents is generated in the output current of . Therefore, after the current signal is superimposed with the even-order harmonic current in the grid-connected current, the even-order harmonic current can be weakened.
  • PWM Pulse Width Modulation
  • the phase of the current signal generated at the output end of the three-level inverter is opposite to that of the even-order harmonic current, so as to balance the bus potential and minimize the Even harmonic currents in grid-connected currents.
  • FIG. 6 is a waveform diagram provided by an embodiment of the present application when the control method of the present application is not adopted
  • FIG. 7 is a waveform diagram provided by an embodiment of the present application when the control method of the present application is adopted.
  • the waveform of the voltage of the positive DC bus is 602, and the waveform of the voltage of the negative DC bus after taking the absolute value is 601. Due to the influence of the even-order harmonic components in the grid-connected current, the energy between the positive and negative DC buses is transferred to each other. , so a clear voltage difference ⁇ U appears between the two waveforms.
  • FIG. 8 is a waveform diagram of the grid-connected current corresponding to FIG. 6 provided by the application
  • FIG. 9 is a waveform diagram of the grid-connected current corresponding to FIG. 7 provided by the application.
  • the grid-connected current is in the form of three-phase alternating current
  • the area 801 in FIG. 8 is the peak of one-phase alternating current in the three-phase alternating current
  • the area 802 is the trough of this phase. Due to the obvious even-order harmonic components in the grid-connected current, the energy between the positive and negative DC buses is transferred to each other, and the waveforms of the peaks and troughs are obviously distorted.
  • the method of the embodiment of the present application can balance the midpoint potential of the three-level inverter busbar and also suppress the even-order harmonic current in the grid-connected current, so that the output The grid-connected current is more standard.
  • FIG. 10 is a flowchart of another method for controlling a three-level inverter provided by an embodiment of the present application.
  • FIG. 11 is another control block diagram provided by this embodiment of the present application.
  • S301-S305 of the method provided by this embodiment of the present application correspond to S201-S205 of the method described in the second embodiment, and the difference is only that the first proportional-integral controller in FIG. 11 in this embodiment is equivalent to the proportional-integral control in FIG. 4 .
  • the device 401 is not described again in this embodiment of the present application.
  • S306 Obtain a second equalization voltage command by using the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter.
  • the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter is obtained, and the second proportional-integral controller 502 is used to generate a second equalizing voltage command U ref_m .
  • the second equalizing voltage command is the common mode voltage of the three-level inverter.
  • S307 Adjust the driving command of the three-level inverter by using the first balanced voltage command and the second balanced voltage command, so that a current signal for reducing the even-order harmonic current is generated in the output current of the three-level inverter.
  • the first balanced voltage command U ref_h and the second balanced voltage command U ref_m are superimposed to generate a balanced voltage composite control command U ref , and the obtained U ref is superimposed with the original control signal of the three-level inverter to generate The drive signal used to drive the three-level inverter.
  • the three-level inverter is driven by the driving signal, so that a current signal for reducing the even-order harmonic current is generated in the output current of the three-level inverter.
  • the drive signal can cause the output current of the three-level inverter to generate a current signal that is in the opposite phase of the even-order harmonic current, thereby balancing the bus potential and reducing the grid-connected current as much as possible. Even harmonic currents.
  • FIG. 12 is a flowchart of still another method for controlling a three-level inverter provided by an embodiment of the present application.
  • the even-order harmonic current in the grid-connected current is less than the preset current threshold, it indicates that the even-order harmonic current has little influence on the potential of the midpoint of the bus, and can be ignored;
  • the equalization command is the three-phase common-mode voltage bus equalization control quantity.
  • the specific description is similar to the second equalization voltage command U ref_m in the above embodiment, which can be generated by the proportional integral controller. .
  • S1202 Adjust the driving command of the three-level inverter by using the equalization command.
  • the equalization command and the original control signal of the three-level inverter are superimposed to generate a driving signal for driving the three-level inverter.
  • the even-order harmonic current in the grid-connected current affects the potential balance of the bus midpoint of the three-level inverter, the positive and The difference between the absolute values of the negative DC bus voltage, combined with the even-order harmonic current in the grid-connected current, determines the balance command, and uses the current balance command to adjust the grid-connected current to ensure the positive and negative bus voltages of the three-level inverter. balance.
  • this method suppresses the harmonics of the grid-connected current, it also improves the adaptability of the three-level inverter to the power grid, and reduces the three-level inverter caused by the unbalanced bus potential when the power grid environment is harsh. Probability of protection shutdown.
  • Embodiment 4 is a diagrammatic representation of Embodiment 4:
  • the embodiment of the present application further provides a control device of the three-level inverter, which will be described in detail below with reference to the accompanying drawings.
  • this figure is a schematic diagram of a control device of a three-level inverter provided by an embodiment of the present application.
  • the apparatus includes a determination unit 1301 and an adjustment unit 1302 .
  • the determining unit 1301 uses the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter and the even-order harmonic current in the grid-connected current to determine an equalization command, and the equalization command is used to make the three-level inverse
  • the output current of the inverter generates a current signal for reducing the even harmonic current.
  • the current signal is in opposite phase to the even harmonic current.
  • the adjusting unit 1302 is used to adjust the grid-connected current by using the equalization command. That is, the grid-connected current loop 404 in FIG. 11 is included.
  • this figure is a schematic diagram of another control device of a three-level inverter provided by an embodiment of the present application.
  • the determining unit 1301 specifically includes: a first coefficient determining subunit 1301a, a second coefficient determining subunit 1301b, and a first instruction determining subunit 1301c.
  • the first coefficient determination subunit 1301a is used for determining the harmonic amplitude coefficient by using the difference value. That is, the first proportional-integral controller 501 shown in FIG. 11 is included.
  • the second coefficient determination subunit 1301b determines the type of the even harmonic current in the grid-connected current, the weighting coefficient corresponding to the even harmonic current of each type, and the influence of the weighting coefficient and the even harmonic on the grid-connected current degree is positively correlated. That is, it includes the detection unit 402 shown in FIG. 11 , and the harmonic weight distribution unit and the harmonic type order selection unit in 403 .
  • the ratio of the weighting coefficients corresponding to each even-order harmonic current is a ratio of the amplitudes of each even-order harmonic current.
  • the first command determination subunit 1301c is configured to determine the equalization command by using the harmonic amplitude coefficient, the type and weight coefficient corresponding to each even-order harmonic current.
  • the first command determination subunit 1301c obtains the equalization command component corresponding to each even-order harmonic current.
  • the equalization command components corresponding to the harmonic currents are superimposed to obtain the equalization command.
  • the adjustment unit 1302 superimposes the equalization command and the grid-connected current to obtain a grid-connected current command, uses the grid-connected current command to obtain a first equalized voltage command, and uses the first equalized voltage command to adjust the three-level
  • the drive command of the inverter generates a current signal for reducing the even-order harmonic current in the output current of the three-level inverter.
  • the implementation corresponds to the control block diagram shown in FIG. 4 .
  • the adjustment unit 1302 superimposes the equalization command and the grid-connected current to obtain the grid-connected current command, uses the grid-connected current command to obtain the first equalized voltage command, and uses the difference to obtain the second equalized voltage command.
  • the second balance voltage command is the balance control quantity of the three-phase common mode voltage bus. And use the first balanced voltage command and the second balanced voltage command to adjust the driving command of the three-level inverter, so that the output current of the three-level inverter generates a current signal for reducing the even harmonic current.
  • the adjustment unit 1302 further includes the second proportional-integral controller 502 shown in FIG. 11 , and this implementation corresponds to the control block diagram shown in FIG. 11 .
  • the determining unit 1301 utilizes the difference when the even-order harmonic current in the grid-connected current is less than the preset current threshold, and/or when the difference is less than the preset voltage threshold The value gets the equalization command.
  • the equalization command is a three-phase common-mode voltage bus equalization control quantity, which is similar to the second equalization voltage command U ref_m in FIG. 11 and can be generated by the second proportional-integral controller 502 .
  • the adjusting unit 1302 adjusts the driving command of the three-level inverter using the equalization command. Specifically, the adjustment unit 1302 superimposes the equalization command and the original control signal of the three-level inverter to generate a driving signal for driving the three-level inverter.
  • the determination unit of the control device uses the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter to represent the deviation of the current bus midpoint potential, and combines the grid-connected current with the difference between the absolute values of the positive and negative DC bus voltage.
  • the even-order harmonic current determines a balance command
  • the adjustment unit uses the current balance command to adjust the grid-connected current, so that a current signal for reducing the even-order harmonic current is generated in the grid-connected current. That is, the current signal generated according to the current balance command and the even-order harmonic current in the grid-connected current can weaken the even-order harmonic current after superposition, thus ensuring the balance of the positive and negative bus voltages of the three-level inverter.
  • the harmonics of the grid-connected current are suppressed, so the adaptability of the three-level inverter to the power grid is also improved, and the probability of shutdown of the three-level inverter due to the unbalanced bus potential when the power grid environment is harsh is reduced.
  • Embodiment 5 is a diagrammatic representation of Embodiment 5:
  • the embodiment of the present application further provides a three-level inverter, which will be described in detail below with reference to the accompanying drawings.
  • this figure is a schematic diagram of a three-level inverter provided by an embodiment of the present application.
  • the illustrated three-level inverter 20 includes: a first bus capacitor C1 , a second bus capacitor C2 , a power conversion circuit 201 and a controller 202 .
  • the first end of the first bus capacitor C1 is connected to the positive DC bus and the first input end of the power conversion circuit 201 , and the second end of the first bus capacitor C1 is connected to the negative DC bus and the power conversion circuit 201 through the second bus capacitor C2
  • the second input terminal of the first bus capacitor C1 is also connected to the third input terminal of the power conversion circuit 201 .
  • the power conversion circuit 201 is used for converting direct current into three-phase alternating current and outputting it.
  • FIG. 16 is a schematic diagram of a power conversion circuit provided by an embodiment of the present application.
  • the figure shows a possible implementation manner of the power conversion circuit, and the working principle of the power conversion circuit is a relatively mature prior art, which will not be repeated in the embodiments of the present application.
  • the controller 202 is configured to use the difference between the absolute values of the positive and negative DC bus voltages and the even-order harmonic current in the grid-connected current to determine an equalization command, and the equalization command is used to generate an output current of the three-level inverter. Current signal for reducing even harmonic currents and regulating grid-connected currents with equalization commands.
  • the current signal is in opposite phase to the even harmonic current.
  • the controller 202 is specifically configured to use the difference to determine the harmonic amplitude coefficient, determine the type of the even-order harmonic current in the grid-connected current, and the weighting coefficient corresponding to the even-order harmonic current of each type.
  • the influence degree of sub-harmonics on the grid-connected current is positively correlated, and the equalization command is determined by using the harmonic amplitude coefficient, the type and weight coefficient corresponding to each even-order harmonic current.
  • the ratio of the weighting coefficients corresponding to each even-order harmonic current is the ratio of the amplitudes of each even-order harmonic current.
  • the controller 202 obtains the equalization command component corresponding to each even harmonic current, and the equalization command component is the product of the amplitude coefficient, the weight coefficient of the even harmonic current and the type; The equalization command components are superimposed to obtain an equalization command.
  • the controller superimposes the balancing command and the grid-connected current to obtain the grid-connected current command, uses the grid-connected current command to obtain the first balancing voltage command, and uses the first balancing voltage command to adjust the driving command of the three-level inverter , so that a current signal for reducing the even harmonic current is generated in the output current of the three-level inverter.
  • the controller superimposes the balancing command and the grid-connected current to obtain the grid-connected current command, uses the grid-connected current command to obtain the first balancing voltage command, and uses the difference to obtain the second balancing voltage command, the second balancing voltage
  • the command is the balance control amount of the three-phase common-mode voltage bus, and the driving command of the three-level inverter is adjusted by using the first balanced voltage command and the second balanced voltage command, so that the output current of the three-level inverter produces A current signal that reduces even harmonic currents.
  • the controller or the like in the embodiments of the present application may be an application specific integrated circuit (Application Specific Integrated Circuit, ASIC), a programmable logic device (Programmable Logic Device, PLD), a digital signal processor (Digital Signal Processor, DSP) or a combination thereof.
  • ASIC Application Specific Integrated Circuit
  • PLD programmable logic device
  • DSP Digital Signal Processor
  • the above-mentioned PLD can be a complex programmable logic device (Complex Programmable Logic Device, CPLD), a field-programmable gate array (Field-programmable Gate Array, FPGA), a general array logic (Generic Array Logic, GAL) or any combination thereof. This is not specifically limited in the application examples.
  • the controller of the three-level inverter uses the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter to represent the deviation of the current bus midpoint potential, and combines and The even-order harmonic current in the grid current determines a balance command, and the grid-connected current is adjusted by using the current balance command, so that a current signal for reducing the even-order harmonic current is generated in the grid-connected current. That is, the current signal generated according to the current balance command and the even-order harmonic current in the grid-connected current can weaken the even-order harmonic current after superposition, thus ensuring the balance of the positive and negative bus voltages of the three-level inverter.
  • the adaptability of the three-level inverter to the power grid is also improved, and the protection of the three-level inverter caused by the unbalanced bus potential when the power grid environment is bad is reduced. probability of shutdown.
  • Embodiment 6 is a diagrammatic representation of Embodiment 6
  • the embodiment of the present application further provides a photovoltaic power generation system, which will be described in detail below with reference to the accompanying drawings.
  • FIG. 17 is a schematic diagram of a photovoltaic power generation system provided by an embodiment of the present application.
  • the photovoltaic power generation system 1700 includes a photovoltaic unit 10 and a three-level inverter 20 .
  • the photovoltaic unit 10 includes a plurality of photovoltaic components, and the output end of the photovoltaic unit 10 is connected to the input end of the three-level inverter 20 .
  • the photovoltaic unit 10 is used to convert light energy into direct current and then transmit it to the three-level inverter 20 .
  • the three-level inverter 20 is used for converting direct current into three-phase alternating current and then outputting it.
  • the controller 202 of the three-level inverter 20 is configured to use the difference between the absolute values of the positive and negative DC bus voltages of the three-level inverter and the even-order harmonic current in the grid-connected current to determine the equalization command,
  • the equalization command is used to generate a current signal for reducing the even-order harmonic current in the output current of the three-level inverter, and the grid-connected current is adjusted by the equalization command.
  • controller 202 For the specific working principle of the controller 202, reference may be made to the relevant descriptions in the above embodiments, and details are not described herein again in this embodiment of the present application.
  • the photovoltaic power generation system includes a three-level inverter, and the controller of the three-level inverter uses the absolute value of the positive and negative DC bus voltages of the three-level inverter
  • the difference value of , and the even-order harmonic current in the grid-connected current determine a balance command, and the grid-connected current is adjusted by using the current balance command, so that a current signal for reducing the even-order harmonic current is generated in the grid-connected current. That is, the current signal generated according to the current balance command and the even-order harmonic current in the grid-connected current can weaken the even-order harmonic current after superposition, thus ensuring the balance of the positive and negative bus voltages of the three-level inverter.
  • the harmonics of the grid-connected current are suppressed, so the adaptability of the three-level inverter to the power grid is also improved, and the protection shutdown caused by the unbalanced bus potential of the three-level inverter when the power grid environment is bad is reduced. probability, and improve the stability of the photovoltaic power generation system.
  • the electronic device for implementing the computer program product includes a processor and a memory, and the processor may refer to one processor, or may include multiple processors.
  • the memory may include volatile memory (English: volatile memory), such as random-access memory (English: random-access memory, abbreviation: RAM); the memory may also include non-volatile memory (English: non-volatile memory), For example, read-only memory (English: read-only memory, abbreviation: ROM), flash memory (English: flash memory), hard disk (English: hard disk drive, abbreviation: HDD) or solid-state hard disk (English: solid-state drive, Abbreviation: SSD); the memory may also comprise a combination of the above-mentioned kinds of memory.
  • the memory may refer to one memory, or may include multiple memories.
  • computer-readable instructions are stored in the memory, and the computer-readable instructions include a plurality of software units, such as the determination unit and the adjustment module in the above embodiments.
  • the processor can perform corresponding operations according to the instructions of each software unit.
  • the operation performed by a software unit actually refers to the operation performed by the processor according to the instruction of the software unit.
  • the processor executes the computer-readable instructions in the memory, it can perform all operations that can be performed by the network device according to the instructions of the computer-readable instructions.
  • At least one (item) refers to one or more, and "a plurality” refers to two or more.
  • “And/or” is used to describe the relationship between related objects, indicating that there can be three kinds of relationships, for example, “A and/or B” can mean: only A, only B, and both A and B exist , where A and B can be singular or plural.
  • the character “/” generally indicates that the associated objects are an “or” relationship.
  • At least one item(s) below” or similar expressions thereof refer to any combination of these items, including any combination of single item(s) or plural items(s).
  • At least one (a) of a, b or c can mean: a, b, c, "a and b", “a and c", “b and c", or "a and b and c" ", where a, b, c can be single or multiple.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

本申请公开了一种三电平逆变器、控制方法及***，涉及电子电力技术领域。其中，该三电平逆变器包括：第一母线电容、第二母线电容、功率变换电路和控制器。第一母线电容的第一端连接正直流母线和功率变换电路的第一输入端，第一母线电容的第二端通过第二母线电容连接负直流母线和功率变换电路的第二输入端，第一母线电容的第二端还连接功率变换电路的第三输入端；功率变换电路用于将直流电转换为三相交流电后输出；控制器用于利用正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，均衡指令用于使三电平逆变器产生均衡正、负直流母线电压的电流信号。该三电平逆变器正、负直流母线的电压能够实现均衡。

Description

一种三电平逆变器、控制方法及*** 技术领域
本申请涉及电力电子技术领域，尤其涉及一种三电平逆变器、控制方法及***。
背景技术
光伏发电是利用半导体界面的光生伏特效应而将光能转变为电能的一种技术，一直以来得到快速发展。光伏逆变器作为光伏发电***中的核心部件，用于将光伏组件产生的直流电转换为交流电。
三电平逆变器作为光伏逆变器的一种，其桥臂电压为三电平，较两电平逆变器多，因其可有效降低如滤波电感等无源器件的体积而被广泛应用。但是，三电平逆变器由于存在母线中点，而母线中点电位的平衡涉及到逆变器功率器件的耐压、并网电流的谐波等诸多指标，因此三电平逆变器的中点电位的均衡控制至关重要。
光伏发电***应用于并网场景时，光伏发电***与电网连接，而电网中会存在较大的电压背景谐波的扰动，电压背景的谐波会造成并网电流含有同频次的电流谐波，进而导致正、负直流母线的电压不均衡，使得直流母线中点的点位产生偏移，威胁逆变器的正常运行。
发明内容
为了解决以上技术问题，本申请提供了一种三电平逆变器、控制方法及***，该三电平逆变器正、负直流母线的电压能够实现均衡。
第一方面，本申请提供了一种三电平逆变器，该三电平逆变器包括第一母线电容、第二母线电容、功率变换电路和控制器。其中，第一母线电容的第一端连接正直流母线和功率变换电路的第一输入端，第一母线电容的第二端通过第二母线电容连接负直流母线和功率变换电路的第二输入端，第一母线电容的第二端还连接功率变换电路的第三输入端；功率变换电路用于将直流电转换为三相交流电后输出；控制器用于利用正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，均衡指令用于使三电平逆变器产生均衡正、负直流母线电压的电流信号。
本申请提供的技术方案充分考虑到了并网电流中的偶次谐波电流对于三电平逆变器的母线中点电位的影响。该三电平逆变器的控制器利用三电平逆变器的正、负直流母线电压的绝对值的差值，表征当前的母线中点电位的偏离情况，并且结合并网电流中的偶次谐波电流确定均衡指令，利用该电流均衡指令调节并网电流。即根据该电流均衡指令产生的电流信号与并网电流中的偶次谐波电流叠加后能够削弱该偶次谐波电流，因此该三电平逆变器的正、负母线电压能够实现均衡，此外同时还抑制了并网电流的谐波，提升了三电平逆变器对电网的适应能力，使得该三电平逆变器兼顾了在恶劣电网环境下的母线均衡控制与并网电流谐波抑制。
结合第一方面，在第一种可能的实现方式中，控制器利用差值确定谐波幅值系数，再确定并网电流中的偶次谐波电流的型次，以及各型次的偶次谐波电流对应的权重系数，权重系数与偶次谐波对并网电流的影响程度正相关，然后利用谐波幅值系数、各偶次谐波电流对应的型次与权重系数，确定均衡指令。
该均衡指令结合了各偶次谐波电流对应的型次与权重系数，能够抑制偶次谐波电流。
结合第一方面，在第二种可能的实现方式中，控制器具体用于获取各偶次谐波电流对应的均衡指令分量，均衡指令分量为所述幅值系数、偶次谐波电流的权重系数与型次的乘积；将各偶次谐波电流对应的均衡指令分量进行叠加以获得均衡指令。
结合第一方面，在第三种可能的实现方式中，控制器具体用于将均衡指令与并网电流叠加获取并网电流指令；利用并网电流指令获取第一均衡电压指令；利用第一均衡电压指令调节三电平逆变器的驱动指令，即将获取的第一均衡电压指令与三电平逆变器原有的控制信号进行叠加以产生用于驱动三电平逆变器的驱动信号，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。
结合第一方面，在第四种可能的实现方式中，控制器将均衡指令与并网电流叠加获取并网电流指令；利用并网电流指令获取第一均衡电压指令；利用差值获取第二均衡电压指令；利用第一均衡电压指令和第二均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低所述偶次谐波电流的电流信号。
其中，第二均衡电压指令为三电平逆变器的共模电压量。将第一均衡电压指令以及第二均衡电压指令进行叠加，生成均衡电压复合控制指令，并将获取的与三电平逆变器原有的控制信号进行叠加以产生用于驱动三电平逆变器的驱动信号。
结合第一方面，在第五种可能的实现方式中，各偶次谐波电流对应的权重系数的比值为各偶次谐波电流的幅值的比值。即权重系数与幅值成正相关，幅值越高，表明对应的偶次谐波电流越大，对于并网电流的影响程度也越大。
结合第一方面，在第六种可能的实现方式中，控制器当并网电流中的偶次谐波电流小于预设电流阈值，和/或当差值小于预设电压阈值时，利用差值获取所述均衡指令。
当并网电流中的偶次谐波电流小于预设电流阈值时，表征此时偶次谐波电流对母线中点的电位影响程度较小，可以忽略不计；当正、负直流母线电压的绝对值的差值小于预设电压阈值时，表征此时母线中点的电位受偶次谐波电流的影响程度较小。因此当满足以上两个条件中的至少一项时，表征此时电网的条件较优，并网电流中的偶次谐波电流的影响较小。因此可以利用该差值获取均衡指令，此时该均衡指令为三相共模电压母线均衡控制量
结合第一方面，在第七种可能的实现方式中，控制器具体用于利用均衡指令调节三电平逆变器的驱动指令。
结合第一方面，在第八种可能的实现方式中，电流信号与偶次谐波电流的相位相反，进而在均衡母线电位的同时，尽量减小并网电流中的偶次谐波电流。
第二方面，本申请还提供了一种逆变器的控制方法，该方法包括：利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，均衡指令用于使三电平逆变器产生均衡正、负直流母线电压的电流信号；利用均衡指令调节并网电流。
该方法利用三电平逆变器的正、负直流母线电压的绝对值的差值，表征当前的母线中点电位的偏离情况，并且结合并网电流中的偶次谐波电流确定均衡指令，利用该电流均衡 指令调节并网电流，进而使得并网电流中产生用于降低该偶次谐波电流的电流信号。即根据该电流均衡指令产生的电流信号与并网电流中的偶次谐波电流叠加后能够削弱该偶次谐波电流，因此保障了三电平逆变器的正、负母线电压的均衡。此外，由于该方法抑制了并网电流的谐波，因此还提升了三电平逆变器对电网的适应能力，降低了三电平逆变器在电网环境恶劣时因为母线电位不均衡而引发保护关机的概率，
结合第二方面，在第一种可能的实现方式中，所述利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，具体包括：利用差值确定谐波幅值系数；确定并网电流中的偶次谐波电流的型次，以及各型次的偶次谐波电流对应的权重系数，权重系数与所述偶次谐波对并网电流的影响程度正相关；利用谐波幅值系数、各偶次谐波电流对应的型次与权重系数确定均衡指令。
结合第二方面，在第二种可能的实现方式中，利用谐波幅值系数、各偶次谐波电流对应的型次与权重系数，确定均衡指令，具体包括：获取各偶次谐波电流对应的均衡指令分量，均衡指令分量为幅值系数、偶次谐波电流的权重系数与型次的乘积；将各偶次谐波电流对应的均衡指令分量进行叠加以获得所述均衡指令。
结合第二方面，在第三种可能的实现方式中，利用均衡指令调节并网电流，具体包括：将均衡指令与并网电流叠加获取并网电流指令；利用并网电流指令获取第一均衡电压指令；利用第一均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。
结合第二方面，在第四种可能的实现方式中，利用均衡指令调节并网电流，具体包括：将均衡指令与并网电流叠加获取并网电流指令；利用并网电流指令获取第一均衡电压指令；利用差值获取第二均衡电压指令，第二均衡电压指令为三电平逆变器的共模电压量；利用第一均衡电压指令和第二均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。
结合第二方面，在第五种可能的实现方式中，各偶次谐波电流对应的权重系数的比值为各所述偶次谐波电流的幅值的比值。
结合第二方面，在第六种可能的实现方式中，利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，具体包括：当并网电流中的偶次谐波电流小于预设电流阈值，和/或当差值小于预设电压阈值时，利用差值获取均衡指令。
结合第二方面，在第七种可能的实现方式中，利用均衡指令调节并网电流，具体包括：利用均衡指令调节三电平逆变器的驱动指令。
结合第二方面，在第八种可能的实现方式中，电流信号与偶次谐波电流的相位相反。
第三方面，本申请还提供了一种逆变器的控制装置，该装置包括：确定单元和调节单元。确定单元用于利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，均衡指令用于使所述三电平逆变器产生均衡正、负直流母线电压的电流信号。调节单元用于利用均衡指令调节并网电流。
结合第三方面，在第一种可能的实现方式中，确定单元具体包括：第一系数确定子单 元、第二系数确定子单元和第一指令确定子单元。第一系数确定子单元用于利用差值确定谐波幅值系数。第二系数确定子单元用于确定并网电流中的偶次谐波电流的型次，以及各型次的偶次谐波电流对应的权重系数，权重系数与偶次谐波对并网电流的影响程度正相关。第一指令确定子单元用于利用所述谐波幅值系数、各偶次谐波电流对应的型次与权重系数，确定均衡指令。
结合第三方面，在第二种可能的实现方式中，第一指令确定子单元具体用于：获取各偶次谐波电流对应的均衡指令分量，均衡指令分量为所述幅值系数、偶次谐波电流的权重系数与型次的乘积；将各偶次谐波电流对应的均衡指令分量进行叠加以获得均衡指令。
结合第三方面，在第三种可能的实现方式中，调节单元具体用于：将均衡指令与并网电流叠加获取并网电流指令；利用并网电流指令获取第一均衡电压指令；利用第一均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。
结合第三方面，在第四种可能的实现方式中，调节单元具体用于：将均衡指令与并网电流叠加获取并网电流指令；利用并网电流指令获取第一均衡电压指令；利用差值获取第二均衡电压指令；利用第一均衡电压指令和第二均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。
结合第三方面，在第五种可能的实现方式中，各偶次谐波电流对应的权重系数的比值为各偶次谐波电流的幅值的比值。
结合第三方面，在第六种可能的实现方式中，确定单元具体用于当并网电流中的偶次谐波电流小于预设电流阈值，和/或当差值小于预设电压阈值时，利用差值获取均衡指令。
结合第三方面，在第七种可能的实现方式中，调节单元具体同于：利用均衡指令调节所述三电平逆变器的驱动指令。
结合第三方面，在第八种可能的实现方式中，电流信号与偶次谐波电流的相位相反。
第四方面，本申请还提供了一种光伏发电***，该光伏发电***包括以上任意实现方式中提供的三电平逆变器，还包括光伏单元。光伏单元包括多个光伏组件，光伏单元的输出端连接三电平逆变器的输入端。光伏单元用于将光能转换为直流电后传输至三电平逆变器。
第五方面，本申请还提供了一种计算机可读存储介质，存储介质上存储有计算程序，所述计算机程序执行时实现以上任意实现方式提供的控制方法。
附图说明
图1为光伏***的示意图；
图2为本申请实施例提供的一种三电平逆变器的控制方法的流程图；
图3为本申请实施例提供的另一种三电平逆变器的控制方法的流程图；
图4为本申请实施例提供的一种控制框图；
图5为本申请实施例提供的一种均衡指令的确定方法的流程图；
图6为本申请实施例提供的未采用本申请的控制方法时的波形图；
图7为本申请实施例提供的采用本申请的控制方法时的波形图；
图8为本申请实施例提供的图6对应的并网电流的波形图；
图9为本申请实施例提供的图7对应的并网电流的波形图；
图10为本申请实施例提供的又一种三电平逆变器的控制方法的流程图；
图11为本申请实施例提供的另一种控制框图；
图12为本申请实施例提供的再一种三电平逆变器的控制方法的流程图；
图13为本申请实施例提供的一种三电平逆变器的控制装置的示意图；
图14为本申请实施例提供的另一种三电平逆变器的控制装置的示意图；
图15为本申请实施例提供的一种三电平逆变器的示意图；
图16为本申请实施例提供的一种功率变换电路的示意图；
图17为本申请实施例提供的一种光伏发电***的示意图。
具体实施方式
为了使本领域技术人员更清楚地理解本申请实施例提供的技术方案，下面先介绍本申请提供的技术方案的应用场景。
参见图1，该图为光伏***的示意图。
图示光伏***包括光伏单元10以及三电平逆变器20，光伏***与电网30连接。
光伏单元10包括多个光伏(PV)组件，多个光伏组件通过串联或者并联的方式连接，例如多个光伏组件可以先串联形成光伏组串，多个光伏组串再串联形成光伏单元10。
三电平逆变器20用于将光伏组件10产生的直流电转换为交流电后传输至电网。光伏***的输出电流以ig表示，电网的电压以Ug表示。
其中，三电平逆变器20包括：母线电容C1和C2，以及功率变换电路201。
正、负直流母线的中点用N表示，中点N的电位的平衡涉及到三电平逆变器的功率器件的耐压、并网电流的谐波等诸多指标，因此三电平逆变器的中点电位的均衡控制至关重要。
为了实现中点电位的均衡，目前可以通过在三电平逆变器20的母线电容C1和C2外接阻性负载的方式强制实现母线均压；或者在正、负直流母线外接开关变换器，当正、负直流母线的电压不均衡时，控制外接开关变换器工作来转移正、负直流母线的能量，以实现中点电位的平衡。
但是尽管采取了以上的措施，当电网的环境较为恶劣时，实际应用中仍然会存三电平逆变器因为母线中点电位不平衡而脱离电网的问题，严重威胁了三电平逆变器的正常可靠运行。
为了解决以上技术问题，本申请提供了一种三电平逆变器、控制方法及***，充分考虑到了并网电流中的偶次谐波电流对于三电平逆变器的母线中点电位的影响。利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，利用该电流均衡指令调节并网电流，进而使得该并网电流中产生用于降低该偶次谐波电流的电流信号，降低了并网电流对于三电平逆变器的影响，因此保障了三电平逆变器的正、负母线电压的均衡。此外，还抑制了并网电流的谐波，因此还提升了三电平逆变器对电网的适应能力，降低了三电平逆变器在电网环境恶劣时因为母线电位不均衡而引发保 护关机的概率。
为了使本领域技术领域的人员更清楚地理解本申请方案，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行描述。
本申请说明中的“第一”、“第二”等用词仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量
在本申请中，除非另有明确的规定和限定，术语“连接”应做广义理解，例如，“连接”可以是固定连接，也可以是可拆卸连接，或成一体；可以是直接连接，也可以通过中间媒介间接连接。
实施例一：
发明人经研究与反复实验发现，对于条件较为恶劣的电网，由于电网的电压U g含有较大的偶次谐波电流，导致三电平逆变器20的并网电流ig亦含有一定量同频次谐波电流，而偶次谐波电流会导致光伏***的正、负直流母线间能量相互转移，进而导致正、负直流母线的电压不均衡，具体的能量转移情况可以参见表1。
表1：谐波电流导致直流母线能量转移对应表
Figure PCTCN2020113953-appb-000001
其中，偶次谐波电流的频率为并网电流的频率的偶数倍，例如2、4、8倍等。
当前的中点电位平衡控制策略存在控制能力上限，当偶次谐波电流因此引起的正、负直流母线的能量转移严重时，目前的策略不足以抑制该问题，最终可能导致直流母线的中点电位偏移，威胁三电平逆变器的正常可靠运行，严重时会导致三电平逆变器批量保护关机，出现脱网现象。
为此，本申请实施例提供了一种三电平逆变器的控制方法，下面结合附图具体说明。
参见图2，该图为本申请实施例提供的一种三电平逆变器的控制方法的流程图。
本申请实施例提供的方法可由三电平逆变器的控制器实现，该方法包括以下步骤：
S101：利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的 偶次谐波电流确定均衡指令，均衡指令用于使三电平逆变器产生均衡正、负直流母线电压的电流信号。
三电平逆变器的正、负直流母线电压的绝对值的差值，表征了此时直流母线中点电位的偏移程度，也表征了当前并网电流中的偶次谐波电流对于母直流线中点的电位的影响，下面举例说明：
假设某一时刻，光伏发电***的直流母线总电压为749.6V，在并网电流的影响下，此时的正直流母线的电压为+353.6V，负直流母线的电压为-396V，则此时所述差值为-42.4V。该差值越大，表征当前的正、负直流母线电压偏移越大，即并网电流中的偶次谐波电流对于正、负直流母线的中点电压影响越严重。
与此同时，还可以实时采样并网电流，并且分析并网电流的谐波信息以获取并网电流中的偶次谐波电流的信息。例如获取偶次谐波电流的幅值信息、型次信息等等。其中，偶次谐波电流的型次表征了偶次谐波电流的频率与并网电流的频率的倍数关系。型次越大，谐波电流的频率相应越大。
根据该差值以及并网电流中的偶次谐波电流确定均衡指令。该均衡指令的作用是使三电平逆变器在并网电流中产生用于降低偶次谐波电流的电流信号，即产生的电流信号削弱了偶次谐波电流对于三电平逆变器的正、负直流母线中点电压的影响。
S102：利用均衡指令调节并网电流。
利用S101中获取的均衡指令控制三电平逆变器的工作状态，以使三电平逆变器的正、负直流母线实现电压的均衡，通过对三电平逆变器的控制，调节了三电平逆变器的输出电流，即调节了并网电流。
综上所述，本申请提供的控制方法，充分考虑到了并网电流中的偶次谐波电流对于三电平逆变器的母线中点电位的影响。利用三电平逆变器的正、负直流母线电压的绝对值的差值，表征当前的直流母线中点电位的偏离情况，并且结合并网电流中的偶次谐波电流确定均衡指令，利用该电流均衡指令调节并网电流，进而使得并网电流中产生用于降低该偶次谐波电流的电流信号。即根据该电流均衡指令产生的电流信号与并网电流中的偶次谐波电流叠加后能够削弱该偶次谐波电流，因此保障了三电平逆变器的正、负母线电压的均衡。此外，由于该方法抑制了并网电流的谐波，因此还提升了三电平逆变器对电网的适应能力，降低了三电平逆变器在电网环境恶劣时因为母线电位不均衡而引发关机的概率，增强了并网友好性，从适应电网走向支撑电网。
实施例二：
下面结合具体的实现方式，说明控制三电平逆变器实现母线电压均衡的原理。
参见图3，该图为本申请实施例提供的另一种三电平逆变器的控制方法的流程图。
为了方便理解，还可以一并参见图4所示的控制框图。
S201：利用正、负直流母线电压的绝对值的差值确定谐波幅值系数。
当三电平逆变器并网后，实时采集正、负直流母线的电压，并获取两者的绝对值的差值ΔU，该偏差量ΔU可以经过比例积分控制器(PI controller)401生成谐波幅值系数Im。该谐波幅值系数表征此时并网电流中的偶次谐波电流的幅值。
S202：确定并网电流中的偶次谐波电流的型次，以及各型次的偶次谐波电流对应的权重系数，权重系数与所述偶次谐波对并网电流的影响程度正相关。
检测单元402实施采样并网电流ig，处理单元403分析并网电流的采样信息，进而获取并网电流中的偶次谐波电流的型次以及各型次的偶次谐波电流对应的权重系数。具体而言，谐波型次选择单元根据并网电流中各次谐波的分布情况，确定各偶次谐波电流型次：
cos(nwt+Δθ n)      (1)
其中，w为基波角频率，Δθ n为谐波型次起始相角，n＝2·i，i∈[-N,N]，其中N为正整数。
谐波权重分配单元确定各型次的偶次谐波电流对应的权重系数k n，权重系数与偶次谐波对并网电流的影响程度正相关，本申请对权重系数的具体分配方式不做具体限定。
在一些实施例中，各偶次谐波电流对应的权重系数的比值为各偶次谐波电流的幅值的比值，即权重系数与幅值成正相关，幅值越高，表明对应的偶次谐波电流越大，对于并网电流的影响程度也越大。因此二次谐波电流的权重系数最大，实际应用中，可以结合三电平逆变器正常工作时对正、负直流母线的电位的具体需求，确定需要考虑的偶次谐波电流的型次，而对于特别高的型次的偶次谐波电流，由于其权重系数极低，对于并网电流的影响可以忽略不计。
S203：利用谐波幅值系数、各偶次谐波电流对应的型次与权重系数，确定均衡指令。
均衡指令结合了各偶次谐波电流对应的型次与权重系数，用于使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号，即均衡指令用于抑制偶次谐波电流。
下面说明一种确定均衡指令的方法。
参见图5，该图为本申请实施例提供的一种均衡指令的确定方法的流程图。
S203a：获取各偶次谐波电流对应的均衡指令分量，均衡指令分量为幅值系数、偶次谐波电流的权重系数与型次的乘积。
均衡指令分量为i j分(t)，即如下式所示：
i j分(t)＝I m·k n·cos(nwt+Δθ n)     (2)
其中，k n∈[-1，1]。
S203b：将各偶次谐波电流对应的均衡指令分量进行叠加以获得均衡指令。
均衡指令为i j(t)，即如下式所示：
Figure PCTCN2020113953-appb-000002
其中，j＝a,b,c。a、b和c分别对应三相交流电中的一相。
在另一些实施例中，还可以将权重系数小于预设权重阈值偶次谐波电流忽略不计，本申请对于预设权重阈值的确定方法与具体数值不做具体限定。
S204：将均衡指令与并网电流叠加获取并网电流指令。
并网电流指令i ref，即如下式所示：
i ref＝i g+i j(t)       (4)
S205：利用并网电流指令获取第一均衡电压指令。
即并网电流指令i ref通过并网电流环路404后生成第一均衡电压指令U ref_h，并网电流环路包括了根据并网电流的采样信息反馈调节三电平逆变器的工作状态的环路，该环路的检测以及控制原理为较为成熟的现有技术，本申请实施例在此不再具体赘述。
S206：利用第一均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。
将获取的U ref_h与三电平逆变器原有的控制信号进行叠加以产生用于驱动三电平逆变器的驱动信号。三电平逆变器中包括有可控开关管，本申请实施例不具体限定可控开关管的类型，例如可以为绝缘栅双极型晶体管(Insulated Gate Bipolar Transistor，IGBT)、金属氧化物半导体场效应晶体管(Metal Oxide Semiconductor Filed Effect Transistor，MOSFET，以下简称MOS管)、SiC MOSFET(Silicon Carbide Metal Oxide Semiconductor，碳化硅场效应管)等。
本申请实施例方法应用于控制器时，控制器通过调节作用于可控开关管的PWM(Pulse Width Modulation，脉冲宽度调制)信号以调节可控开关管的工作状态，使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。因此该电流信号与并网电流中的偶次谐波电流叠加后能够削弱偶次谐波电流。
在一些实施例中，为了更好地削弱偶次谐波电流，三电平逆变器输出端产生的电流信号与偶次谐波电流的相位相反，进而在均衡母线电位的同时，尽量减小并网电流中的偶次谐波电流。
本申请实施例以上步骤的划分及顺序仅是为了方便，并不构成对于本申请的限定，本领域的技术人员在具体实施时可以进行适当的调整，例如其中的S201和S202的顺序可以调换。
综上所述，利用本申请实施例的方法，保障了三电平逆变器的正、负母线电压的均衡。此外，由于该方法抑制了并网电流的谐波，因此还提升了三电平逆变器对电网的适应能力，降低了三电平逆变器在电网环境恶劣时因为母线电位不均衡而引发保护关机的概率。为了使本领域技术人员搞清楚的了解本申请方案的优点，下面结合附图具体说明。
一并参见图6和图7。其中，图6为本申请实施例提供的未采用本申请的控制方法时的波形图，图7为本申请实施例提供的采用本申请的控制方法时的波形图。
图6中正直流母线的电压的波形为602，负直流母线的电压取绝对值后的波形为601，由于并网电流中的偶次谐波分量的影响，导致正、负直流母线间能量相互转移，因此两个波形之间出现了明显的电压差ΔU。
而图7采用了本申请的控制方法之后，有效均衡了母线中点电位，使逆变器正、负直流母线电压均衡。
一并参见图8和图9,。其中，图8为本申请提供的图6对应的并网电流的波形图，图9为本申请提供的图7对应的并网电流的波形图。
并网电流的形式为三相交流电，图8中的区域801为三相交流电中的一相交流电的波峰，区域802为该相电的波谷。由于并网电流中存在明显的偶次谐波分量，导致正、负直流母线间能量相互转移，进而导致波峰与波谷的波形出现了较为明显的畸变。
而参见图9中的区域901以及区域902可知，利用本申请实施例的方法在均衡三电平逆变器母线中点电位的同时还抑制了并网电流中的偶次谐波电流，使得输出的并网电流更加标准。
实施例三：
下面结合另一种具体的实现方式，说明控制三电平逆变器实现母线电压均衡的原理。
参见图10，该图为本申请实施例提供的又一种三电平逆变器的控制方法的流程图。
为了方便理解，还可以参见图11，该图为本申请实施例提供的另一种控制框图。
本申请实施例提供的方法的S301-S305对应于实施例二中所述方法的S201-S205，区别仅在于本实施例图11中的第一比例积分控制器相当于图4中的比例积分控制器401，本申请实施例在此不再赘述。
通过以上的S301-S305，获取第一均衡电压指令U ref_h。
S306：利用三电平逆变器的正、负直流母线电压的绝对值的差值获取第二均衡电压指令。
获取三电平逆变器的正、负直流母线电压的绝对值的差值，经过第二比例积分控制器502生成第二均衡电压指令U ref_m。该第二均衡电压指令为所述三电平逆变器的共模电压量。
S307：利用第一均衡电压指令和第二均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。
将第一均衡电压指令U ref_h以及第二均衡电压指令U ref_m进行叠加，生成均衡电压复合控制指令U ref，并将获取的U ref与三电平逆变器原有的控制信号进行叠加以产生用于驱动三电平逆变器的驱动信号。
利用该驱动信号驱动三电平逆变器，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。在一些实施例中，该驱动信号可以使三电平逆变器的输出电流中产生与偶次谐波电流反相的电流信号，进而在均衡母线电位的同时，尽量减小并网电流中的偶次谐波电流。
参见图12，该图为本申请实施例提供的再一种三电平逆变器的控制方法的流程图。
本申请实施例提供的方法包括以下步骤：
S1201：当并网电流中的偶次谐波电流小于预设电流阈值，和/或当差值小于预设电压阈值时，利用差值获取均衡指令。
当并网电流中的偶次谐波电流小于预设电流阈值时，表征此时偶次谐波电流对母线中点的电位影响程度较小，可以忽略不计；
当正、负直流母线电压的绝对值的差值小于预设电压阈值时，表征此时母线中点的电位受偶次谐波电流的影响程度较小。
因此当满足以上两个条件中的至少一项时，表征此时电网的条件较优，并网电流中的偶次谐波电流的影响较小。因此可以利用该差值获取均衡指令，此时该均衡指令为三相共模电压母线均衡控制量，具体说明类似于以上实施例中的第二均衡电压指令U ref_m，可以通过比例积分控制器生成。
S1202：利用均衡指令调节三电平逆变器的驱动指令。
将均衡指令与三电平逆变器原有的控制信号进行叠加以产生用于驱动三电平逆变器的驱动信号。
综上所述，利用本申请实施例提供的方法，当并网电流中的偶次谐波电流影响三电平逆变器的母线中点电位均衡时，利用三电平逆变器的正、负直流母线电压的绝对值的差值，结合并网电流中的偶次谐波电流确定均衡指令，利用该电流均衡指令调节并网电流，保障了三电平逆变器的正、负母线电压的均衡。此外，由于该方法抑制了并网电流的谐波，因此还提升了三电平逆变器对电网的适应能力，降低了三电平逆变器在电网环境恶劣时因为母线电位不均衡而引发保护关机的概率。
实施例四：
基于以上实施例提供的三电平逆变器的控制方法，本申请实施例还提供了一种三电平逆变器的控制装置，下面结合附图具体说明。
参见图13，该图为本申请实施例提供的一种三电平逆变器的控制装置的示意图。
该装置包括确定单元1301和调节单元1302。
其中，确定单元1301利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，均衡指令用于使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。
在一种较优的实现方式中，电流信号与偶次谐波电流的相位相反。
调节单元1302用于利用均衡指令调节并网电流。即包括图11中的并网电流环路404。
参见图14，该图为本申请实施例提供的另一种三电平逆变器的控制装置的示意图。
其中，确定单元1301具体包括：第一系数确定子单元1301a、第二系数确定子单元1301b和第一指令确定子单元1301c。
其中，第一系数确定子单元1301a，用于利用差值确定谐波幅值系数。即包括图11中所示的第一比例积分控制器501。
第二系数确定子单元1301b确定并网电流中的偶次谐波电流的型次，以及各型次的偶次谐波电流对应的权重系数，权重系数与偶次谐波对并网电流的影响程度正相关。即包括图11中所示的检测单元402，以及403中的谐波权重分配单元和谐波型次选择单元。
在一些实施例中，各偶次谐波电流对应的权重系数的比值为各偶次谐波电流的幅值的比值。
第一指令确定子单元1301c用于利用谐波幅值系数、各偶次谐波电流对应的型次与权重系数，确定均衡指令。
具体的，第一指令确定子单元1301c获取各偶次谐波电流对应的均衡指令分量，均衡指令分量为幅值系数、偶次谐波电流的权重系数与型次的乘积，并将各偶次谐波电流对应的均衡指令分量进行叠加以获得均衡指令。
在一些可能的实现方式中，调节单元1302将均衡指令与并网电流叠加获取并网电流指令，利用所述并网电流指令获取第一均衡电压指令，并利用第一均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。此时该实现方式对应于图4所示的控制框图。
在另一些可能的实现方式中，调节单元1302将均衡指令与并网电流叠加获取并网电流指令，利用并网电流指令获取第一均衡电压指令，利用差值获取第二均衡电压指令，该第二均衡电压指令为三相共模电压母线均衡控制量。并利用第一均衡电压指令和第二均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低所述偶次谐波电流的电流信号。即调节单元1302还包括图11中所示的第二比例积分控制器502，该实现方式对应于图11所示的控制框图。
继续参见图13，在另一种可能的实现方式中，确定单元1301当并网电流中的偶次谐波电流小于预设电流阈值，和/或当差值小于预设电压阈值时，利用差值获取均衡指令。
此时电网的条件较优，并网电流中的偶次谐波电流的影响较小。该均衡指令为三相共模电压母线均衡控制量，类似于图11中的第二均衡电压指令U ref_m，可以通过第二比例积分控制器502生成。
调节单元1302利用均衡指令调节三电平逆变器的驱动指令。具体的，调节单元1302将均衡指令与三电平逆变器原有的控制信号进行叠加以产生用于驱动三电平逆变器的驱动信号。
综上所述，该控制装置的确定单元利用三电平逆变器的正、负直流母线电压的绝对值的差值，表征当前的母线中点电位的偏离情况，并且结合并网电流中的偶次谐波电流确定均衡指令，调节单元利用该电流均衡指令调节并网电流，进而使得并网电流中产生用于降低该偶次谐波电流的电流信号。即根据该电流均衡指令产生的电流信号与并网电流中的偶次谐波电流叠加后能够削弱该偶次谐波电流，因此保障了三电平逆变器的正、负母线电压的均衡。此外还抑制了并网电流的谐波，因此还提升了三电平逆变器对电网的适应能力，降低了三电平逆变器在电网环境恶劣时因母线电位不均衡而关机的概率。
实施例五：
基于以上实施例提供的三电平逆变器的控制方法，本申请实施例还提供了一种三电平逆变器，下面结合附图具体说明。
参见图15，该图为本申请实施例提供的一种三电平逆变器的示意图。
图示三电平逆变器20包括：第一母线电容C1、第二母线电容C2、功率变换电路201和控制器202。
其中，第一母线电容C1的第一端连接正直流母线和功率变换电路201的第一输入端，第一母线电容C1的第二端通过第二母线电容C2连接负直流母线和功率变换电路201的第二输入端，第一母线电容C1的第二端还连接功率变换电路201的第三输入端。
功率变换电路201用于将直流电转换为三相交流电后输出。
参见图16，该图为本申请实施例提供的一种功率变换电路的示意图。
图示为功率变换电路的一种可能的实现方式，关于功率变换电路的工作原理为较为成熟的现有技术，本申请实施例在此不再赘述。
控制器202用于利用正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，均衡指令用于使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号，并利用均衡指令调节并网电流。
在一种较优的实施例中，电流信号与偶次谐波电流的相位相反。
控制器202具体用于利用差值确定谐波幅值系数，确定并网电流中的偶次谐波电流的型次，以及各型次的偶次谐波电流对应的权重系数，权重系数与偶次谐波对并网电流的影响程度正相关，并利用谐波幅值系数、各偶次谐波电流对应的型次与权重系数，确定均衡指令。
在一种可能的实现方式中，各偶次谐波电流对应的权重系数的比值为各偶次谐波电流的幅值的比值。
进一步的，控制器202获取各偶次谐波电流对应的均衡指令分量，均衡指令分量为幅值系数、偶次谐波电流的权重系数与型次的乘积；将各偶次谐波电流对应的均衡指令分量进行叠加以获得均衡指令。
在一些实施例中，控制器将均衡指令与并网电流叠加获取并网电流指令，利用并网电流指令获取第一均衡电压指令，利用第一均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。
在另一些实施例中，控制器将均衡指令与并网电流叠加获取并网电流指令，利用并网电流指令获取第一均衡电压指令，利用差值获取第二均衡电压指令，该第二均衡电压指令为三相共模电压母线均衡控制量，利用第一均衡电压指令和第二均衡电压指令调节三电平逆变器的驱动指令，以使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号。
本申请实施例中的控制器等可以为专用集成电路(Application Specific Integrated Circuit，ASIC)、可编程逻辑器件(Programmable Logic Device，PLD)、数字信号处理器(Digital Signal Processor，DSP)或其组合。上述PLD可以是复杂可编程逻辑器件(Complex Programmable Logic Device，CPLD)、现场可编程逻辑门阵列(Field-programmable Gate Array，FPGA)、通用阵列逻辑(Generic Array Logic,GAL)或其任意组合，本申请实施例对此不作具体限定。
综上所述，该三电平逆变器的控制器利用三电平逆变器的正、负直流母线电压的绝对值的差值，表征当前的母线中点电位的偏离情况，并且结合并网电流中的偶次谐波电流确定均衡指令，利用该电流均衡指令调节并网电流，进而使得并网电流中产生用于降低该偶次谐波电流的电流信号。即根据该电流均衡指令产生的电流信号与并网电流中的偶次谐波电流叠加后能够削弱该偶次谐波电流，因此保障了三电平逆变器的正、负母线电压的均衡。此外，由于还抑制了并网电流的谐波，因此还提升了三电平逆变器对电网的适应能力，降低了三电平逆变器在电网环境恶劣时因为母线电位不均衡而引发保护关机的概率。
实施例六：
基于以上实施例提供的三电平逆变器，本申请实施例还提供了一种光伏发电***，下面结合附图具体说明。
参见图17，该图为本申请实施例提供的一种光伏发电***的示意图。
该光伏发电***1700包括光伏单元10和三电平逆变器20。
光伏单元10包括多个光伏组件，光伏单元10的输出端连接三电平逆变器20的输入端。
光伏单元10用于将光能转换为直流电后传输至三电平逆变器20。
三电平逆变器20用于将直流电转换为三相交流电后输出。
该三电平逆变器20的控制器202用于利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，均衡指令用于使三电平逆变器的输出电流中产生用于降低偶次谐波电流的电流信号，并利用均衡指令调节并网电流。
关于控制器202的具体工作原理可以参见以上实施例中的相关说明，本申请实施例在此不再赘述。
综上所述，本申请实施例提供的光伏发电***包括了三电平逆变器，该三电平逆变器的控制器利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，利用该电流均衡指令调节并网电流，进而使得并网电流中产生用于降低该偶次谐波电流的电流信号。即根据该电流均衡指令产生的电流信号与并网电流中的偶次谐波电流叠加后能够削弱该偶次谐波电流，因此保障了三电平逆变器的正、负母线电压的均衡。此外还抑制了并网电流的谐波，因此还提升了三电平逆变器对电网的适应能力，降低了三电平逆变器在电网环境恶劣时因为母线电位不均衡而引发保护关机的概率，提升了光伏发电***的稳定性。
通过以上的实施方式的描述可知，本领域的技术人员可以清楚地了解到上述实施例方法中的全部或部分步骤可借助软件加通用硬件平台的方式来实现。基于这样的理解，本申请的技术方案可以以软件产品的形式体现出来，该计算机软件产品可以存储在存储介质中，如只读存储器(英文：read-only memory，ROM)/RAM、磁碟、光盘等，包括若干程序代码或指令用以使得电子设备(可以是个人计算机，服务器，或者诸如路由器等网络通信设备等)执行本申请各个实施例或者实施例的某些部分所述的方法。
用于实现该计算机程序产品的电子设备包括处理器和存储器，处理器可以是指一个处理器，也可以包括多个处理器。存储器可以包括易失性存储器(英文：volatile memory)，例如随机存取存储器(英文：random-access memory，缩写：RAM)；存储器也可以包括非易失性存储器(英文：non-volatile memory)，例如只读存储器(英文：read-only memory，缩写：ROM)，快闪存储器(英文：flash memory)，硬盘(英文：hard disk drive，缩写：HDD)或固态硬盘(英文：solid-state drive，缩写：SSD)；存储器还可以包括上述种类的存储器的组合。存储器可以是指一个存储器，也可以包括多个存储器。在一个具体实施方式中，存储器中存储有计算机可读指令，所述计算机可读指令包括多个软件单元，例如以上实施例中的确定单元和调节模块。处理器执行各个软件单元后可以按照各个软件单元的指示进行相应的操作。在本实施例中，一个软件单元所执行的操作实际上是指处理器根据所述软件单元的指示而执行的操作。处理器执行存储器中的计算机可读指令后，可以按照所述计算机可读指令的指示，执行网络设备可以执行的全部操作。
本说明书中的各个实施例均采用递进的方式描述，各个实施例之间相同相似的部分互相参见即可，每个实施例重点说明的都是与其他实施例的不同之处。尤其，对于装置实施例和设备实施例而言，由于其基本相似于方法实施例，所以描述得比较简单，相关之处参见方法实施例的部分说明即可。以上所描述的设备及装置实施例仅仅是示意性的，其中作 为分离部件说明的模块可以是或者也可以不是物理上分开的，作为模块显示的部件可以是或者也可以不是物理模块，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部模块来实现本实施例方案的目的。本领域普通技术人员在不付出创造性劳动的情况下，即可以理解并实施。
应当理解，在本申请中，“至少一个(项)”是指一个或者多个，“多个”是指两个或两个以上。“和/或”，用于描述关联对象的关联关系，表示可以存在三种关系，例如，“A和/或B”可以表示：只存在A，只存在B以及同时存在A和B三种情况，其中A，B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。“以下至少一项(个)”或其类似表达，是指这些项中的任意组合，包括单项(个)或复数项(个)的任意组合。例如，a，b或c中的至少一项(个)，可以表示：a，b，c，“a和b”，“a和c”，“b和c”，或“a和b和c”，其中a，b，c可以是单个，也可以是多个。
以上所述，以上实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围。

Claims (19)

  1. 一种三电平逆变器，其特征在于，包括：第一母线电容、第二母线电容、功率变换电路和控制器；
    所述第一母线电容的第一端连接正直流母线和所述功率变换电路的第一输入端，所述第一母线电容的第二端通过所述第二母线电容连接负直流母线和所述功率变换电路的第二输入端，所述第一母线电容的第二端还连接所述功率变换电路的第三输入端；
    所述功率变换电路用于将直流电转换为三相交流电后输出；
    所述控制器，用于利用所述正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，所述均衡指令用于使所述三电平逆变器产生均衡所述正、负直流母线电压的电流信号。
  2. 根据权利要求1述的三电平逆变器，其特征在于，所述控制器具体用于：
    利用所述差值确定谐波幅值系数；
    确定并网电流中的偶次谐波电流的型次，以及各型次的偶次谐波电流对应的权重系数，所述权重系数与所述偶次谐波对所述并网电流的影响程度正相关；
    利用所述谐波幅值系数、各偶次谐波电流对应的型次与权重系数，确定所述均衡指令。
  3. 根据权利要求2述的三电平逆变器，其特征在于，所述控制器具体用于：
    获取各所述偶次谐波电流对应的均衡指令分量，所述均衡指令分量为所述幅值系数、偶次谐波电流的权重系数与型次的乘积；
    将各所述偶次谐波电流对应的均衡指令分量进行叠加以获得所述均衡指令。
  4. 根据权利要求3述的三电平逆变器，其特征在于，所述控制器具体用于：
    将所述均衡指令与所述并网电流叠加获取并网电流指令；
    利用所述并网电流指令获取第一均衡电压指令；
    利用所述第一均衡电压指令调节所述三电平逆变器的驱动指令，以使所述三电平逆变器的输出电流中产生用于降低所述偶次谐波电流的电流信号。
  5. 根据权利要求3述的三电平逆变器，其特征在于，所述控制器具体用于：
    将所述均衡指令与所述并网电流叠加获取并网电流指令；
    利用所述并网电流指令获取第一均衡电压指令；
    利用所述差值获取第二均衡电压指令；
    利用所述第一均衡电压指令和第二均衡电压指令调节所述三电平逆变器的驱动指令，以使所述三电平逆变器的输出电流中产生用于降低所述偶次谐波电流的电流信号。
  6. 根据权利要求2-5中任意一项所述的三电平逆变器，其特征在于，各所述偶次谐波电流对应的权重系数的比值为各所述偶次谐波电流的幅值的比值。
  7. 根据权利要求1述的三电平逆变器，其特征在于，所述控制器，具体用于：
    当所述并网电流中的偶次谐波电流小于预设电流阈值，和/或当所述差值小于预设电压阈值时，利用所述差值获取所述均衡指令。
  8. 根据权利要求7述的三电平逆变器，其特征在于，所述控制器，具体用于：
    利用所述均衡指令调节所述三电平逆变器的驱动指令。
  9. 根据权利要求8述的三电平逆变器，其特征在于，所述电流信号与所述偶次谐波电流的相位相反。
  10. 一种三电平逆变器的控制方法，其特征在于，所述方法包括：
    利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，所述均衡指令用于使所述三电平逆变器产生均衡所述正、负直流母线电压的电流信号；
    利用所述均衡指令调节所述并网电流。
  11. 根据权利要求10所述的控制方法，其特征在于，所述利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，具体包括：
    利用所述差值确定谐波幅值系数；
    确定并网电流中的偶次谐波电流的型次，以及各型次的偶次谐波电流对应的权重系数，所述权重系数与所述偶次谐波对所述并网电流的影响程度正相关；
    利用所述谐波幅值系数、各偶次谐波电流对应的型次与权重系数，确定所述均衡指令。
  12. 根据权利要求11所述的控制方法，其特征在于，所述利用所述谐波幅值系数、各偶次谐波电流对应的型次与权重系数，确定所述均衡指令，具体包括：
    获取各所述偶次谐波电流对应的均衡指令分量，所述均衡指令分量为所述幅值系数、偶次谐波电流的权重系数与型次的乘积；
    将各所述偶次谐波电流对应的均衡指令分量进行叠加以获得所述均衡指令。
  13. 根据权利要求12所述的控制方法，其特征在于，所述利用所述均衡指令调节所述并网电流，具体包括：
    将所述均衡指令与所述并网电流叠加获取并网电流指令；
    利用所述并网电流指令获取第一均衡电压指令；
    利用所述第一均衡电压指令调节所述三电平逆变器的驱动指令，以使所述三电平逆变器的输出电流中产生用于降低所述偶次谐波电流的电流信号。
  14. 根据权利要求12所述的控制方法，其特征在于，所述利用所述均衡指令调节所述并网电流，具体包括：
    将所述均衡指令与所述并网电流叠加获取并网电流指令；
    利用所述并网电流指令获取第一均衡电压指令；
    利用所述差值获取第二均衡电压指令，所述第二均衡电压指令为所述三电平逆变器的共模电压量；
    利用所述第一均衡电压指令和第二均衡电压指令调节所述三电平逆变器的驱动指令，以使所述三电平逆变器的输出电流中产生用于降低所述偶次谐波电流的电流信号。
  15. 根据权利要求11-14中任意一项所述的控制方法，其特征在于，各所述偶次谐波电流对应的权重系数的比值为各所述偶次谐波电流的幅值的比值。
  16. 根据权利要求10所述的控制方法，其特征在于，所述利用三电平逆变器的正、负直流母线电压的绝对值的差值，以及并网电流中的偶次谐波电流确定均衡指令，具体包括：
    当所述并网电流中的偶次谐波电流小于预设电流阈值，和/或当所述差值小于预设电压 阈值时，利用所述差值获取所述均衡指令。
  17. 根据权利要求16所述的控制方法，其特征在于，所述利用所述均衡指令调节所述并网电流，具体包括：
    利用所述均衡指令调节所述三电平逆变器的驱动指令。
  18. 根据权利要求10所述的控制方法，其特征在于，所述电流信号与所述偶次谐波电流的相位相反。
  19. 一种光伏发电***，其特征在于，所述光伏发电***包括权利要求1-9中任意一项所述的三电平逆变器，还包括光伏单元；
    所述光伏单元包括多个光伏组件，所述光伏单元的输出端连接所述三电平逆变器的输入端；
    所述光伏单元，用于将光能转换为直流电后传输至所述三电平逆变器。
PCT/CN2020/113953 2020-09-08 2020-09-08 一种三电平逆变器、控制方法及*** WO2022051892A1 (zh)

Priority Applications (5)

Application Number Priority Date Filing Date Title
PCT/CN2020/113953 WO2022051892A1 (zh) 2020-09-08 2020-09-08 一种三电平逆变器、控制方法及***
CN202311192543.3A CN117220532A (zh) 2020-09-08 2020-09-08 一种三电平逆变器、控制方法及***
EP20952681.3A EP4195489A4 (en) 2020-09-08 2020-09-08 THREE STAGE INVERTER AND CONTROL METHOD AND SYSTEM
CN202080024643.3A CN114982121B (zh) 2020-09-08 2020-09-08 一种三电平逆变器、控制方法及***
US18/179,098 US20230238896A1 (en) 2020-09-08 2023-03-06 Three-level inverter, control method, and system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2020/113953 WO2022051892A1 (zh) 2020-09-08 2020-09-08 一种三电平逆变器、控制方法及***

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US18/179,098 Continuation US20230238896A1 (en) 2020-09-08 2023-03-06 Three-level inverter, control method, and system

Publications (1)

Publication Number Publication Date
WO2022051892A1 true WO2022051892A1 (zh) 2022-03-17

Family

ID=80630188

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2020/113953 WO2022051892A1 (zh) 2020-09-08 2020-09-08 一种三电平逆变器、控制方法及***

Country Status (4)

Country Link
US (1) US20230238896A1 (zh)
EP (1) EP4195489A4 (zh)
CN (2) CN114982121B (zh)
WO (1) WO2022051892A1 (zh)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115241926A (zh) * 2022-09-16 2022-10-25 深圳市首航新能源股份有限公司 母线电压控制方法、母线平衡控制方法及其***

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117595262A (zh) * 2023-10-31 2024-02-23 天津科林电气有限公司 一种光伏并网逆变器无功谐波抑制方法
CN117439395A (zh) * 2023-12-14 2024-01-23 江苏纳通能源技术有限公司 母线均压方法、装置、设备及存储介质

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102291030A (zh) * 2011-08-16 2011-12-21 南京国睿新能电子有限公司 三电平光伏并网逆变器直流电压平衡控制方法
CN107317494A (zh) * 2017-08-09 2017-11-03 厦门科华恒盛股份有限公司 一种三电平变换器及其母线中点的平衡控制方法及装置
CN108832827A (zh) * 2018-06-06 2018-11-16 合肥工业大学 一种具有最小开关损耗的三电平逆变器的非连续脉宽调制方法
CN110943638A (zh) * 2019-12-12 2020-03-31 华中科技大学 一种中点电压平衡变开关频率控制方法及***
CN111009924A (zh) * 2019-12-26 2020-04-14 中国工程物理研究院材料研究所 一种单相三电平逆变器滤波电感值宽范围变化补偿方法

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3248321B2 (ja) * 1993-11-10 2002-01-21 富士電機株式会社 ３レベルインバータの制御回路
JP6544170B2 (ja) * 2015-09-16 2019-07-17 株式会社明電舎 ３レベルインバータの制御装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102291030A (zh) * 2011-08-16 2011-12-21 南京国睿新能电子有限公司 三电平光伏并网逆变器直流电压平衡控制方法
CN107317494A (zh) * 2017-08-09 2017-11-03 厦门科华恒盛股份有限公司 一种三电平变换器及其母线中点的平衡控制方法及装置
CN108832827A (zh) * 2018-06-06 2018-11-16 合肥工业大学 一种具有最小开关损耗的三电平逆变器的非连续脉宽调制方法
CN110943638A (zh) * 2019-12-12 2020-03-31 华中科技大学 一种中点电压平衡变开关频率控制方法及***
CN111009924A (zh) * 2019-12-26 2020-04-14 中国工程物理研究院材料研究所 一种单相三电平逆变器滤波电感值宽范围变化补偿方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP4195489A4 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115241926A (zh) * 2022-09-16 2022-10-25 深圳市首航新能源股份有限公司 母线电压控制方法、母线平衡控制方法及其***
CN115241926B (zh) * 2022-09-16 2023-02-28 深圳市首航新能源股份有限公司 母线电压控制方法、母线平衡控制方法及其***

Also Published As

Publication number Publication date
CN114982121B (zh) 2023-10-13
US20230238896A1 (en) 2023-07-27
CN117220532A (zh) 2023-12-12
EP4195489A1 (en) 2023-06-14
EP4195489A4 (en) 2023-09-27
CN114982121A (zh) 2022-08-30

Similar Documents

Publication Publication Date Title
WO2022051892A1 (zh) 一种三电平逆变器、控制方法及***
JP5474772B2 (ja) ３レベル中性点固定変換装置及びその制御方法
CN109495001B (zh) 模块化并联三电平Vienna整流器、控制***及方法
US8471514B2 (en) Adaptive harmonic reduction apparatus and methods
WO2015165191A1 (zh) 一种三相双模式逆变器的稳态控制方法
JP5452330B2 (ja) 電力変換装置
US9312788B2 (en) Control device of power conversion unit and method of controlling power conversion unit
CN105226982B (zh) 一种基于中点电流的三电平npc逆变器中点电位均衡控制方法
CN110572057B (zh) 一种极低开关频率下的电流源变流器特定谐波抑制方法
US11146181B2 (en) Control method and apparatus for common-mode modulated wave of single-phase five-level inverter
CN106105007B (zh) 多电平功率转换器和用于控制多电平功率转换器的方法
CN112332426A (zh) 基于mmc技术的统一电能质量调节器***及控制方法
CN112994067B (zh) 模块化多电平换流器的能量控制方法
US10320306B1 (en) Matrix converter system with current control mode operation
WO2024031184A1 (en) Constant-frequency single-carrier sensor-less modulation for the three level flying capacitor multicell converter
CN105119314B (zh) 一种用于功率单元直流电压平衡控制的动态切换方法
CN107994796B (zh) 单相变流器的控制方法以及装置
CN107769602B (zh) 三电平逆变器中性点电位自平衡开关信号获取方法及装置
CN112583289B (zh) 用于电流源型整流器并联运行上下母线电流协同控制方法
CN111969875A (zh) 一种减小三相并联电压源型逆变器循环电流的方法
WO2017034028A1 (ja) インバータの制御方法及び制御装置、並びにインバータ装置
WO2024150437A1 (ja) モジュラー・マルチレベル電力変換器
CN212463086U (zh) 一种基于功率交互的逆变器并联装置
US11843327B2 (en) Power conversion device with current hysteresis band control
JP7049294B2 (ja) 自励式電力変換器の電流制御系の設計方法、自励式電力変換器の制御装置、並びに自励式電力変換器

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20952681

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2020952681

Country of ref document: EP

Effective date: 20230309

NENP Non-entry into the national phase

Ref country code: DE