WO2019037545A1 - 换流站接入直流电网的控制方法、控制器及存储介质 - Google Patents

换流站接入直流电网的控制方法、控制器及存储介质 Download PDF

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Publication number
WO2019037545A1
WO2019037545A1 PCT/CN2018/094236 CN2018094236W WO2019037545A1 WO 2019037545 A1 WO2019037545 A1 WO 2019037545A1 CN 2018094236 W CN2018094236 W CN 2018094236W WO 2019037545 A1 WO2019037545 A1 WO 2019037545A1
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Prior art keywords
converter
voltage
sub
module
mmc
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PCT/CN2018/094236
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English (en)
French (fr)
Inventor
吴亚楠
杨杰
李帅
朱思丞
韩乃峥
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全球能源互联网研究院有限公司
国家电网有限公司
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Publication of WO2019037545A1 publication Critical patent/WO2019037545A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Definitions

  • the present invention relates to the field of flexible direct current transmission technologies, and in particular, to a control method, a controller and a storage medium for a converter station to be connected to a DC power grid.
  • renewable energy power generation has developed rapidly, such as wind power generation and solar power generation.
  • These power generation devices have the characteristics of small installed capacity, relatively distributed distribution, and principle AC grid.
  • the traditional current source converter station can only work in the active inverter state, and the short-circuit capacity of the converter station is small, which cannot meet the grid connection requirements of these new energy sources.
  • MMC Modular-Multilevel-Converter
  • FIG. 1 it is a schematic diagram of the basic structure of the MMC, that is, the three-phase bridge arm of the MMC is obtained by SM cascade.
  • the three-phase MMC consists of three phase units of the same structure, three phase units are connected in parallel; each phase unit is divided into upper and lower arms, a total of 6 bridge arms; each bridge arm is composed of N SM and one bridge arm reactance The devices are connected in series.
  • a voltage source converter station using an MMC converter technology is referred to as an MMC converter station.
  • MMC converter station considering the flexible expansion of the DC grid, how to connect the MMC converter station to the DC grid online will become a common problem in the future. If a reasonable MMC converter station can not be used to access the DC grid control strategy of different voltage levels online, the inrush current generated when the MMC converter station is connected will be too large, which will damage the equipment and affect the safe and stable operation of the entire DC grid. .
  • the embodiments of the present invention are directed to a control method, a controller, and a storage medium for a converter station to be connected to a DC power grid, so as to solve the problem of excessive surge current generated when the converter station is connected to the DC power grid.
  • An embodiment of the present invention provides a control method for a converter station to access a DC power grid, including the following steps:
  • the first DC side of the DC/DC converter is connected to be connected Connected to the DC grid to increase the transmission power of the DC/DC converter to the rated transmission power of the DC/DC converter.
  • the AC source that utilizes the MMC converter station charges the first sub-module of the MMC converter station, and includes the following steps:
  • the first sub-module of all the MMC converter stations is unlocked and charged according to the state in which the first sub-module is locked and charged.
  • the latching charging of all the first submodules includes the following steps:
  • the first sub-module is charged by an uncontrolled charging method (such as an AC system through a diode), and the voltage on the DC side of the MMC converter station is raised to a line voltage peak of the AC source.
  • an uncontrolled charging method such as an AC system through a diode
  • the unlocking and charging the first sub-module of all the MMC converter stations according to the state in which the first sub-module is locked and charged includes the following steps:
  • the first sub-module is charged by using a constant DC voltage and a constant reactive power control method, and the voltage on the DC side of the MMC converter station is raised to a rated working voltage of the MMC converter station.
  • the charging of the DC/DC converter by the charged MMC converter station includes the following steps:
  • the third sub-module of the DC/DC converter is unlocked and charged according to an alternating voltage in the DC/DC converter.
  • the second sub-module of all the DC/DC converters is unlocked and charged, and the AC voltage in the DC/DC converter is established, including: using a constant AC voltage and/or a fixed frequency control.
  • the method and adjusting the amount of input of the second sub-module establish an AC voltage in the DC/DC converter.
  • the unlocking and charging the third sub-module of the DC/DC converter according to the AC voltage in the DC/DC converter includes the following steps:
  • the third sub-module is charged by a constant DC voltage and a constant reactive power control method to increase a voltage of the first DC side of the DC/DC converter to a rated operating voltage of the DC/DC converter.
  • the controlling the transmission power of the DC/DC converter so that the transmission power of the DC/DC converter is increased to the rated transmission power of the DC/DC converter, including: using a fixed active power and The method of reactive power controls the transmission power of the DC/DC converter.
  • the method before the step of charging the first submodule of the MMC converter station by using the AC source of the MMC converter station, the method further includes: initializing the MMC converter station and the DC/DC converter step.
  • the embodiment of the invention further provides a control device for the converter station to be connected to the DC power grid, comprising:
  • a first charging module configured to charge the first sub-module of the MMC converter station by using an AC source of the MMC converter station
  • a first determining module configured to determine whether a capacitor voltage of all the first submodules is raised to a rated working voltage of the first submodule
  • the second charging module is configured to charge the DC/DC converter by using the charged MMC converter station when the capacitance voltage of all the first sub-modules is raised to the rated working voltage of the first sub-module;
  • a second determining module configured to determine whether a capacitor voltage of a submodule of all the DC/DC converters is raised to a rated operating voltage of a submodule of the DC/DC converter
  • a networking module configured to: when the capacitance voltage of all of the sub-modules of the DC/DC converter is boosted to a rated operating voltage of a sub-module of the DC/DC converter, the first of the DC/DC converters The DC side is connected to the DC power grid to be connected, and the DC/DC converter transmits power to the rated transmission power of the DC/DC converter.
  • the first charging module includes:
  • a first charging submodule configured to latch and charge all of the first submodules
  • a first determining submodule configured to determine whether a voltage on a DC side of the MMC converter station reaches a peak value of a line voltage of the AC source
  • a first setting module configured to set a state of all the first submodules to an unlocked state if the determination result is yes;
  • a second charging sub-module configured to charge the first sub-module by using a constant DC voltage and a fixed reactive power control method to increase a voltage of a DC side of the MMC converter station to a rated operation of the MMC converter station Voltage.
  • the second charging module includes:
  • a third charging submodule configured to unlock and charge the second submodule of all the DC/DC converters to establish an AC voltage in the DC/DC converter
  • a fourth charging submodule configured to perform uncontrolled charging of the third submodule of the DC/DC converter by using the AC voltage
  • a second determining submodule configured to determine whether a voltage of the first DC side of the DC/DC converter reaches a peak value of a line voltage of the AC source
  • a second setting module configured to set a state of all the third submodules to an unlocked state if the determination result is yes;
  • a fifth charging submodule configured to charge the third submodule by using a constant DC voltage and a constant reactive power control method to boost a voltage of the first DC side of the DC/DC converter to the DC/ The rated operating voltage of the DC converter.
  • control device further includes:
  • An initialization module configured to initialize the MMC converter station and the DC/DC converter.
  • Embodiments of the present invention also provide a controller including at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the one processor, The instructions are executed by the at least one processor to cause the at least one processor to perform a control method of the converter station to access a DC grid in an embodiment of the present invention.
  • a control method for an MMC converter station to be connected to a DC power grid includes the following steps: charging an first sub-module of the MMC converter station by using an AC source of the MMC converter station; Whether the capacitance voltage of the first sub-module is raised to the rated working voltage of the first sub-module; when the capacitance voltage of all the first sub-modules is raised to the rated working voltage of the first sub-module, using the charged
  • the MMC converter station charges a DC/DC converter; determines whether a capacitor voltage of all sub-modules of the DC/DC converter is boosted to a rated operating voltage of a sub-module of the DC/DC converter; When the capacitance voltage of the submodule of the DC/DC converter is raised to the rated operating voltage of the submodule of the DC/DC converter, the first DC side of the DC/DC converter is connected to the to-be-connected
  • the DC power grid is connected to control the transmission power of the DC/DC converter such that the transmission power
  • the ordered charging control of the MMC converter station and the DC/DC converter adopted in the embodiment of the invention can effectively reduce the inrush current of the MMC converter station connected to the DC grid, thereby facilitating the smooth access of the MMC converter station to the DC grid.
  • the project is practical.
  • Charging the sub-module includes the steps of: latching charging all of the first sub-modules; and unlocking and charging the first sub-module of all the MMC converter stations according to the state of the first sub-module latching charging.
  • the inrush current generated when the AC source of the MMC converter station charges the first sub-module can be effectively reduced, and the MMC commutation is easy to be realized.
  • the AC source of the station smoothly charges the first sub-module, thereby increasing the service life of the first sub-module.
  • the method for controlling an MMC converter station to be connected to a DC power grid includes the following steps: A second sub-module of the DC/DC converter performs unlocking charging to establish an AC voltage in the DC/DC converter; and according to an AC voltage in the DC/DC converter, the DC/DC converter is The three sub-modules are unlocked and charged.
  • the inrush current when the MMC converter station is connected to the DC/DC converter can be reduced, and the MMC converter station can be easily accessed to smoothly access the DC. /DC converter.
  • a control device for an MMC converter station to be connected to a DC power grid includes: a first charging module configured to utilize an AC source of the MMC converter station as a first child of the MMC converter station The module is configured to determine whether the capacitance voltage of all the first sub-modules is raised to the rated working voltage of the first sub-module; and the second charging module is configured to be all the first sub-modules When the capacitor voltage is raised to the rated working voltage of the first sub-module, the charged MMC converter station is used to charge the DC/DC converter; and the second judging module is configured to determine all the DC/DC conversions.
  • the networking module is configured to increase the capacitance voltage of the sub-modules of all the DC/DC converters to the
  • the first DC side of the DC/DC converter is connected to the DC grid to be connected to increase the transmission power of the DC/DC converter to the rated operating voltage of the sub-module of the DC/DC converter Rated transmission work of DC/DC converter rate.
  • FIG. 1 is a schematic diagram of a basic structure of an MMC according to an embodiment of the present invention.
  • FIG. 2 is a topological schematic diagram of a DC/DC converter according to an embodiment of the present invention.
  • FIG. 3 is a schematic structural diagram of a submodule of an MMC formed by a half H bridge according to an embodiment of the present invention
  • FIG. 4 is a schematic diagram of an operating state of a submodule in an MMC according to an embodiment of the present invention.
  • FIG. 5 is a schematic topological diagram of a DC power grid according to an embodiment of the present invention.
  • FIG. 6 is a schematic flowchart 1 of a method for controlling an MMC converter station to be connected to a DC power grid according to an embodiment of the present invention
  • FIG. 7 is a second schematic flowchart of a method for controlling an MMC converter station to be connected to a DC power grid according to an embodiment of the present disclosure
  • FIG. 8 is a schematic flowchart 3 of a method for controlling an MMC converter station to be connected to a DC power grid according to an embodiment of the present invention
  • FIG. 9 is a schematic structural diagram 1 of a control device for an MMC converter station connected to a DC power grid according to an embodiment of the present invention
  • FIG. 10 is a schematic structural diagram 2 of a control device for an MMC converter station connected to a DC power grid according to an embodiment of the present invention
  • FIG. 11 is a schematic structural diagram of a controller according to an embodiment of the present invention.
  • the isolated MMC commutation of different voltage levels can be realized by the high voltage and large capacity DC/DC converter.
  • the DC/DC converter is a traditional half-bridge DC/DC converter based on MMC.
  • the structure is shown in Figure 2. It consists of two sets of MMC connected by a transformer. The AC sides of the two sets of MMC are connected by a transformer, and their corresponding The DC side is respectively a first DC side connected to the DC grid to be connected and a second DC side connected to the DC side of the MMC converter station.
  • the submodule in the MMC converter station is referred to as a first submodule; the submodule in the DC/DC converter is divided into: a submodule in a group of MMCs connected to the DC side of the MMC converter station.
  • a sub-module in a group of MMCs connecting the DC/DC converter to the DC grid is referred to as a third sub-module.
  • each bridge arm of the MMC is formed by connecting N SMs and a bridge arm reactor in series.
  • the structure of the SM mainly has a half H bridge structure and an H bridge structure as well as a double clamp type submodule structure.
  • the SM structure in the embodiment of the present invention is selected from, but not limited to, a half-H bridge structure.
  • FIG. 3 shows a schematic structural diagram of a sub-module of the MMC composed of a half-H bridge. As shown in FIG.
  • the sub-module composed of the half-H bridge is mainly
  • the two fully-controlled high-frequency switches IGBT1 and IGBT2 are respectively composed of diodes VD1 and VD2 which are anti-parallel with the high-frequency switch, and a sub-capacitor storage capacitor C.
  • Figure 4 shows the working status of the sub-modules in the MMC.
  • the working mode of the sub-modules can be divided into three states according to the switching states of the two high-frequency switching tubes of the sub-modules and the current direction of the sub-modules. , 6 modes.
  • IGBT1 and IGBT2 give a turn-off signal
  • the sub-module is in a latched state
  • the sub-module is in an unlocked state
  • IGBT2 gives a turn-on signal
  • IGBT1 gives
  • the shutdown signal is asserted, the submodule is in the resected state.
  • the three types of SM parameters of the six modes are shown in Table 1, in which the given IGBT turn-on signal is recorded as 1, the given IGBT turn-off signal is recorded as 0, and the actual on-state of the IGBT is recorded as 1, The actual off state of the IGBT is recorded as 0; the on state of VD is denoted by 1, and the off state of VD is denoted as 0; the voltage on the storage capacitor of the submodule is denoted as Uc.
  • Mode 1 in the latched state occurs only when the submodule capacitor is charged when the MMC is started, and mode 2 in the latched state is used when the submodule capacitor is bypassed at the time of the fault.
  • the SM can operate in different modes to unlock and cut off the SM.
  • the three phase units are connected in parallel, and the operation principle of each phase unit is the same.
  • the sum of the number of SMs in which the upper and lower arms are unlocked in the three phases a, b, and c is N, that is, half of the total number of SMs in each phase; since the three phase units are connected in parallel Therefore, the DC side voltage Udc is equal to the voltage of each phase bridge arm, which is NUC; for the AC side, although the total number of SMs in the unlocked state in each phase is fixed, the unlocking and excision of each SM in the upper and lower arms is performed. Different distributions can obtain different output voltages. Therefore, the AC side three-phase voltage whose amplitude and phase are both satisfactory can be obtained by reasonable control of the SM unlocking state in the upper and lower arms of each phase.
  • FIG. 5 it is a DC grid topology diagram of an embodiment of the present invention, which includes both a radial structure and a ring structure.
  • the voltage value in FIG. 5 is an example, and the protection range of the present invention is not limited thereto.
  • the MMC converter station is C1, and the DC grid to be connected online is a DC grid connected to the first DC side of the DC/DC converter.
  • the MMC converter station is an active station; the DC/DC converter is a traditional half-bridge DC/DC converter based on MMC, and the end connected to the DC grid to be connected is DC1, which is connected to the DC side of the isolated MMC station.
  • One end is DC2; there are several DC circuit breakers connected between DC2 and the isolated MMC station.
  • the embodiment of the invention provides a control method for an MMC converter station to be connected to a DC grid, which can be used in a controller. As shown in FIG. 6, the control method includes the following steps:
  • step S11 the first sub-module of the MMC converter station is charged by using the AC source of the MMC converter station.
  • the MMC converter station includes an AC voltage source G1, and the voltage source is electrically connected to the AC side of the MMC. Therefore, the first sub-module of the MMC converter station can be charged by using G1, that is, The capacitor in the first sub-module of the MMC converter station is charged by G1 such that the capacitor voltage in the first sub-module rises.
  • step S12 it is determined whether the capacitance voltage of all the first sub-modules is raised to the rated working voltage of the first sub-module; if the determination result is yes, step S13 is performed; otherwise, other operations are performed.
  • the MMC sub-module after the MMC sub-module is selected, its rated operating voltage is also determined, and the rated operating voltage is stored in the controller for subsequent comparison.
  • the controller can perform real-time measurement on the capacitance voltage of the first sub-module, and determine the measurement result and the rated working voltage of the pre-stored MMC sub-module, thereby determining whether the capacitance voltage of the first sub-module is The rated operating voltage of the first submodule has been reached.
  • the other operations in this embodiment may be that the capacitor voltage of the first submodule is cyclically measured by the controller, or the capacitor voltage of the first submodule is measured by the controller at intervals.
  • step S13 the DC/DC converter is charged by the charged MMC converter station.
  • the charged MMC converter station is used to charge the DC/DC converter to increase the voltage of the DC/DC converter.
  • Step S14 determining whether the capacitance voltage of the submodules of all the DC/DC converters is raised to the rated operating voltage of the submodule of the DC/DC converter; if the determination result is yes, executing step S15; otherwise, continuing to DC/ The DC converter is charged until the capacitance voltage of the submodules of all DC/DC converters is boosted to the rated operating voltage of the submodules of the DC/DC converter.
  • the DC/DC converter in this embodiment includes two sets of MMCs connected by a transformer, wherein each of the three bridge arms of the MMC includes several sub-modules.
  • the sub-module structure in the DC/DC converter is the same as the sub-module structure in the MMC converter station, that is, is selected from, but not limited to, a half-H bridge structure.
  • the DC/DC converter sub-module After the DC/DC converter sub-module is selected, its rated operating voltage is also determined, and the rated operating voltage is stored in the controller for subsequent comparison.
  • the controller can be used to measure the capacitance voltage of the DC/DC converter sub-module in real time, and the measurement result is judged with the pre-stored rated voltage of the DC/DC converter sub-module, thereby determining the DC. Whether the capacitance voltage of the /DC converter submodule has reached the rated operating voltage of the DC/DC converter submodule.
  • the other operations in this embodiment may be that the capacitor voltage of the DC/DC converter sub-module is cyclically measured by the controller, or the capacitor voltage of the DC/DC converter sub-module may be performed by the controller at intervals. measuring.
  • step S15 the first DC side of the DC/DC converter is connected to the DC grid to be connected, and the transmission power of the DC/DC converter is increased to the rated transmission power of the DC/DC converter.
  • the capacitance voltage of the submodules of all DC/DC converters when the capacitance voltage of the submodules of all DC/DC converters is raised to the rated operating voltage of the submodules of the DC/DC converter, it indicates that the submodules of the DC/DC converter have been charged.
  • the first DC side of the DC/DC converter is connected to the DC grid to be connected by the controller, and the transmission power of the DC/DC converter is controlled, so that the transmission power is increased to the rated transmission of the DC/DC converter. power.
  • the rated transmission power of the DC/DC converter is previously stored in the controller.
  • the ordered charging control of the MMC converter station and the DC/DC converter can effectively reduce the inrush current of the MMC converter station connected to the DC grid, thereby facilitating the smooth access of the MMC converter station to the DC grid, engineering practice Strong.
  • the embodiment of the invention also provides a control method for the MMC converter station to be connected to the DC grid, which is used in the controller. As shown in FIG. 7, the control method includes the following steps:
  • step S21 the first sub-module of the MMC converter station is charged by using the AC source of the MMC converter station.
  • step S21 includes the following steps:
  • step S211 all the first sub-modules are latched and charged.
  • the first sub-module of the MMC converter station is latched and charged by the AC source of the MMC converter station, so that the capacitor voltage of the first sub-module is increased, that is, the voltage of the first sub-module is increased, thereby improving the MMC exchange.
  • the voltage on the DC side of the station is improved.
  • Step S212 unlocking and charging the first sub-module of all the MMC converter stations according to the state in which the first sub-module is locked and charged.
  • the first sub-module can be set in the controller, and when the voltage on the DC side of the MMC converter station reaches the first preset voltage, the state of the first sub-module is changed to unlock charging.
  • the first preset voltage may be a line voltage peak of the MMC converter station, or may be a phase voltage peak of the MMC converter station.
  • Step S22 determining whether the capacitance voltage of all the first sub-modules is raised to the rated working voltage of the first sub-module. In the case where the determination result is YES, step S23 is performed; otherwise, other operations are performed. It is the same as step S12 in Embodiment 1, and will not be described again.
  • step S23 the charged MMC converter station is used to charge the DC/DC converter.
  • the charged MMC converter station is used to charge the DC/DC converter, including the following steps:
  • Step S231 unlocking and charging the second sub-module of all DC/DC converters to establish an AC voltage in the DC/DC converter.
  • the state of the second sub-module of the DC/DC converter is set to an unlocked state by the controller. While unlocking, increase the number of sub-modules put into the upper and lower arms of a group of MMCs connected to the MMC converter station to match the DC-side voltage of the MMC converter station, and then gradually reduce the MMC converter station.
  • the method of reducing the number of sub-modules input by the upper and lower arms is large, and the current impact of the MMC converter station on the second sub-module at the unlocking moment can be reduced.
  • the second DC side of the DC/DC converter is electrically connected to the MMC converter station, that is, the charged and charged MMC converter station is used to unlock and charge the second sub-module of the DC/DC converter, thereby gradually establishing DC/DC.
  • the AC voltage in the converter is not limited to the DC voltage in the converter.
  • the AC voltage in the DC/DC converter is established by using a constant AC voltage control method. That is, the controller pre-sets that the MMC converter station after charging is used to unlock and charge the second sub-module of the DC/DC converter is a constant AC voltage control.
  • Step S232 unlocking and charging the third sub-module of the DC/DC converter according to the AC voltage in the DC/DC converter.
  • the two sets of MMC of the DC/DC converter are electrically connected by a transformer, and the AC voltage at both ends of the transformer is in the process of unlocking and charging the second sub-module of the DC/DC converter after the charged MMC converter station is charged. Gradually established. During the establishment of the AC voltage, the third sub-module of the DC/DC converter is unlocked and charged to increase the voltage of the first DC side of the DC/DC converter.
  • Step S24 determining whether the capacitance voltage of the submodules of all the DC/DC converters is raised to the rated working voltage of the submodule of the DC/DC converter; if the determination result is yes, executing step S25; otherwise, performing other operations .
  • Step S25 connecting the first DC side of the DC/DC converter to the DC power grid to be connected, and increasing the transmission power of the DC/DC converter to the rated transmission power of the DC/DC converter.
  • the control method of the active power and the reactive power is adopted to improve the transmission power of the DC/DC converter. That is, the way in which the controller pre-sets the transmission power of the DC/DC converter is fixed power and reactive power control.
  • the embodiment of the invention also provides a control method for the MMC converter station to be connected to the DC grid, which is used in the controller. As shown in FIG. 8, the control method includes the following steps:
  • step S30 the MMC converter station and the DC/DC converter are initialized.
  • the state of each submodule in the MMC converter station and the DC/DC converter is set to a latched state by the controller, and in addition, a DC open circuit in the circuit connecting the MMC converter station and the DC/DC converter is connected.
  • the state of the device is set to close, thereby ensuring that the MMC converter station and the DC/DC converter are in an electrically connected state.
  • step S31 the first sub-module of the MMC converter station is charged by using the AC source of the MMC converter station.
  • step S31 comprises the following steps:
  • Step S311 charging the first sub-module by using an uncontrolled charging method, and increasing the voltage of the DC side of the MMC converter station to the line voltage peak of the AC source.
  • the first sub-module before the AC source of the MMC converter station is charged for the first sub-module of the MMC converter station, the first sub-module is in a locked state, that is, only VD1 and VD2 in the first sub-module are in working state, and VD1 And VD2 is an uncontrollable component, that is, when the AC source of the MMC converter station starts as the first submodule, it is an uncontrolled charging method.
  • the AC source of the MMC converter station is used to charge the first sub-module to increase the voltage on the DC side of the MMC converter station.
  • step S312 it is determined whether the voltage on the DC side of the MMC converter station reaches the line voltage peak value of the AC source. If the result of the determination is YES, step S313 is performed; otherwise, step S311 is performed.
  • the line voltage peak value of the AC source of the MMC converter station is stored in advance in the controller.
  • the voltage of the DC side of the MMC converter station is measured in real time by the controller, and the measurement result is compared with the peak value of the line voltage of the AC source stored in advance, so that it can be determined whether the voltage on the DC side of the MMC converter station has reached the line of the AC source. Voltage peak.
  • step S313 the states of all the first submodules are set to the unlocked state.
  • the state of all the first sub-modules is set to the unlock state by the controller, so as to facilitate the first sub-sub The module is charged.
  • Step S314 charging the first sub-module by using a constant DC voltage and a fixed reactive power control method, and increasing the voltage on the DC side of the MMC converter station to the rated working voltage of the MMC converter station.
  • the first sub-module set to the unlock state is charged by using the constant DC voltage and the constant reactive power control method, so that the voltage on the DC side of the MMC converter station is raised to the rated working voltage of the MMC converter station. That is, in the embodiment, when the first sub-module in the unlocked state is charged, the control method set by the controller is a constant DC voltage and a constant reactive power control method.
  • the second sub-module in the DC/DC converter since the MMC converter station and the DC/DC converter are already in an electrical connection state, while charging the first sub-module of the MMC converter station, the second sub-module in the DC/DC converter The voltage is also boosted at the same time, thus ensuring a gradual increase in the voltage of the second sub-module in the DC/DC converter.
  • Step S32 determining whether the capacitance voltage of all the first sub-modules is raised to the rated working voltage of the first sub-module. If the result of the determination is YES, step S33 is performed; otherwise, step S314 is performed. The same as step S22 in the second embodiment, and the details are not described again.
  • step S33 the charged MMC converter station is used to charge the DC/DC converter.
  • the voltage of the second sub-module in the DC/DC converter has been improved.
  • the charged MMC converter station is used to charge the DC/DC converter, that is, based on the existing voltage of the sub-module in the DC/DC converter, the voltage is again boosted, thereby avoiding direct utilization.
  • the MMC converter station charges the DC/DC converter, so that the voltage of the DC/DC converter is gradually increased from zero, thereby reducing the inrush current generated when the MMC converter station charges the DC/DC converter, achieving smooth charging. the goal of.
  • step S33 includes the following steps:
  • Step S331 unlocking and charging the second sub-module of all DC/DC converters to establish an AC voltage in the DC/DC converter.
  • step S231 in the second embodiment unlocking and charging the second sub-module of all DC/DC converters to establish an AC voltage in the DC/DC converter.
  • Step S332 using the AC voltage to perform uncontrolled charging on the third sub-module of the DC/DC converter.
  • the third sub-module is in a locked state, only the diode in the circuit of the third sub-module is in operation, and the diode is an uncontrollable component, that is, the third sub-module of the DC/DC converter is charged by using an alternating voltage.
  • the method is uncontrolled charging.
  • Step S333 determining whether the voltage of the first DC side of the DC/DC converter reaches the peak value of the line voltage of the AC source. If the result of the determination is YES, step S334 is performed; otherwise, step S332 is performed.
  • the voltage of the first DC side of the DC/DC converter is measured in real time by the controller, and the voltage is compared with the peak value of the line voltage of the AC source of the pre-stored MMC converter station, thereby obtaining Whether the voltage reaches the line voltage peak of the AC source of the MMC converter station.
  • step S334 the states of all the third submodules are set to the unlocked state.
  • the state of the third submodule is set to an unlocked state by the controller.
  • Step S335 charging the third sub-module by using a constant DC voltage and a constant reactive power control method to increase the voltage of the first DC side of the DC/DC converter to the rated working voltage of the DC/DC converter.
  • the method for charging the third sub-module by the controller is a constant DC voltage and a constant reactive power control, thereby boosting the voltage of the first DC side of the DC/DC converter to DC/DC conversion.
  • the rated operating voltage of the device is a constant DC voltage and a constant reactive power control, thereby boosting the voltage of the first DC side of the DC/DC converter to DC/DC conversion.
  • step S34 it is judged whether the capacitance voltage of the submodules of all the DC/DC converters is raised to the rated operating voltage of the submodules of the DC/DC converter. In the case where the determination result is YES, step S35 is performed; otherwise, step S33 is performed. It is the same as step S34 in Embodiment 2, and will not be described again.
  • Step S35 connecting the first DC side of the DC/DC converter to the DC power grid to be connected, and increasing the transmission power of the DC/DC converter to the rated transmission power of the DC/DC converter.
  • the embodiment provides a control device for the MMC converter station to be connected to the DC grid, as shown in FIG. 9, comprising:
  • the first charging module 41 is configured to charge the first sub-module of the MMC converter station by using an AC source of the MMC converter station.
  • the first determining module 42 is configured to determine whether the capacitance voltage of all the first submodules is raised to the rated working voltage of the first submodule.
  • the second charging module 43 is configured to charge the DC/DC converter by using the charged MMC converter station when the capacitance voltage of all the first sub-modules is raised to the rated operating voltage of the first sub-module.
  • the second determining module 44 is configured to determine whether the capacitance voltage of the sub-modules of all the DC/DC converters is boosted to the rated operating voltage of the sub-modules of the DC/DC converter.
  • the networking module 45 is configured to: when the capacitance voltage of the submodules of all the DC/DC converters is raised to the rated operating voltage of the submodules of the DC/DC converter, the first DC side of the DC/DC converter is to be Connected to the DC grid to increase the transmission power of the DC/DC converter to the rated transmission power of the DC/DC converter.
  • the ordered charging control of the MMC converter station and the DC/DC converter adopted in the embodiment of the invention can effectively reduce the inrush current of the MMC converter station connected to the DC grid, thereby facilitating the smooth access of the MMC converter station to the DC grid.
  • the project is practical.
  • the first charging module 41 includes:
  • the first charging submodule 411 is configured to perform latching charging on all of the first submodules.
  • the first determining sub-module 412 is configured to determine whether the voltage on the DC side of the MMC converter station reaches the line voltage peak of the AC source.
  • the first setting module 413 is configured to set the state of all the first submodules to an unlocked state when the determination result is YES.
  • the second charging sub-module 414 is configured to charge the first sub-module by using a constant DC voltage and a constant reactive power control method, and improve the voltage on the DC side of the isolated MMC converter station to the rated working voltage of the isolated MMC converter station.
  • the second charging module 43 includes:
  • the third charging sub-module 431 is configured to unlock and charge the second sub-module of all the DC/DC converters to establish an AC voltage in the DC/DC converter.
  • the fourth charging sub-module 432 is configured to perform uncontrolled charging of the third sub-module of the DC/DC converter by using an alternating voltage.
  • the second determining sub-module 433 is configured to determine whether the voltage of the first DC side of the DC/DC converter reaches a line voltage peak of the AC source.
  • the second setting module 434 is configured to set the state of all the third sub-modules to the unlocked state if the determination result is YES.
  • the fifth charging sub-module 435 is configured to charge the third sub-module by using a constant DC voltage and a constant reactive power control method to increase the voltage of the first DC side of the DC/DC converter to the DC/DC converter. Operating Voltage.
  • the MMC converter station is connected to the control device of the DC power grid, and further includes:
  • the initialization module 40 is configured to initialize the MMC converter station and the DC/DC converter.
  • the present embodiment provides a controller configured to perform a control method for an MMC converter station to access a DC power grid according to an embodiment of the present invention.
  • a schematic diagram of the hardware structure of the controller includes one or more processors 51 and a memory 52.
  • One processor 51 is taken as an example in FIG.
  • the processor 51 and the memory 52 may be connected by a bus or other means, and the connection by a bus is taken as an example in FIG.
  • the processor 51 can be a Central Processing Unit (CPU).
  • the processor 51 can also be another general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or Other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., or a combination of the above various types of chips.
  • the general purpose processor may be a microprocessor or the processor or any conventional processor or the like.
  • the memory 52 is used as a non-transitory computer readable storage medium for storing non-transitory software programs, non-transitory computer executable programs, and modules, such as the control of the MMC converter station connected to the DC grid in the embodiment of the present invention.
  • the processor 51 executes various functional applications and data processing of the server by running non-transitory software programs, instructions and modules stored in the memory 52, that is, implementing control of the MMC converter station in the above embodiment to access the DC grid. method.
  • the memory 52 may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application required for at least one function; and the storage data area may store a preset of the first sub-module of the preset MMC converter station. Operating voltage, line voltage peak of the AC source of the MMC converter station, rated operating voltage of the submodule of the DC/DC converter, and rated transmission power of the DC/DC converter.
  • memory 52 can include high speed random access memory, and can also include non-transitory memory, such as at least one magnetic disk storage device, flash memory device, or other non-transitory solid state storage device.
  • the memory 52 can optionally include a memory remotely located relative to the processor 51 that can be connected via a network to a control system to be connected to the DC grid.
  • networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.
  • the one or more modules are stored in the memory 52, and when executed by the one or more processors 51, a control method for the MMC converter station to access the DC grid in the embodiment of the present invention is performed.
  • the embodiment of the present invention further provides a non-transitory computer storage medium, where the computer storage medium stores computer executable instructions, and the computer executable instructions can execute the MMC converter station according to the embodiment of the present invention to access the DC power grid. Control method.
  • the storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), a flash memory, a hard disk (Hard). Disk Drive (HDD) or Solid State Drive (SSD), etc.; the storage medium may also include a combination of the above types of memories.
  • the storage medium may be a magnetic disk, an optical disk, a read only memory (ROM), or a random access memory (RAM).

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Abstract

一种换流站接入直流电网的控制方法、控制器及存储介质，其中方法包括：利用MMC换流站的交流源为MMC换流站的第一子模块充电（S11）；判断所有第一子模块的电容电压是否提升至其额定工作电压（S12）；当判断结果为是时，利用充电后的MMC换流站为DC/DC变换器充电（S13）；判断所有DC/DC变换器的子模块的电容电压是否提升至其额定工作电压（S14）；当判断结果为是时，将DC/DC变换器的第一直流侧与待接入直流电网相连，控制DC/DC变换器的传输功率，使得传输功率提升至DC/DC变换器的额定传输功率（S15）。该方法能够有效降低MMC换流站接入直流电网的冲击电流，从而易于实现MMC换流站平滑接入直流电网。

Description

换流站接入直流电网的控制方法、控制器及存储介质
相关申请的交叉引用
本申请基于申请号为201710717287.3、申请日为2017年08月21日的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本发明涉及柔性直流输电技术领域，尤其涉及一种换流站接入直流电网的控制方法、控制器及存储介质。
背景技术
随着化石能源的日益枯竭和环境承载能力的日益减弱，可再生能源发电得到了迅速发展，如风能发电、太阳能发电等。这些发电装置具有单个装机容量小、分布比较分散、原理交流电网等特点。与交流主网并网时，由于传统的电流源换流站只能工作在有源逆变状态、换流站短路容量小等缺点，并不能满足这些新能源的并网要求。
基于高压、大功率、全控型电力电子器件(如绝缘栅双极型晶体管(Insulated Gate Bipolar Transistor，IGBT))的电压源换流站，由于其灵活、经济、可控性、高质量输电方式等优点，成为了直流电网发展的主流趋势。其中，基于电压源换流站技术目前主要采用模块化多电平换流器(Modular-Multilevel-Converter，MMC)变流技术，其采用各相级联的子模块(Submodule，SM)电压叠加的方式输出高电压。如图1所示，为MMC的基本结构示意图，即MMC的三相桥臂是由SM级联所得。三相MMC由三个结构相同的相单元组成，三个相单元并联连接；每个相单元均分为上下桥臂，共6个桥臂；每个桥臂由N个SM和一个桥臂电抗器串联而成。
相关技术中，将采用MMC变流技术的电压源换流站称之为MMC换流站。其中，考虑到直流电网可灵活扩展的性质，因此，如何将MMC换流站在线接入直流电网将成为今后普遍存在的问题。若不能采取合理的MMC换流站在线接入不同电压等级的直流电网的控制策略，将导致MMC换流站接入时产生的冲击电流过大，损坏设备且影响整个直流电网的安全、稳定运行。
发明内容
有鉴于此，本发明实施例期望提供一种换流站接入直流电网的控制方法、控制器及存储介质，以解决换流站接入直流电网时产生的冲击电流过大的问题。
本发明实施例提供了一种换流站接入直流电网的控制方法，包括以下步骤：
利用MMC换流站的交流源为所述MMC换流站的第一子模块充电；
判断所有所述第一子模块的电容电压是否提升至所述第一子模块的额定工作电压；
当所有所述第一子模块的电容电压提升至所述第一子模块的额定工作电压时，利用充电后的所述MMC换流站为(Direct Current，DC)/DC变换器充电；
判断所有所述DC/DC变换器的子模块的电容电压是否提升至所述DC/DC变换器的子模块的额定工作电压；
当所有所述DC/DC变换器的子模块的电容电压提升至所述DC/DC变换器的子模块的额定工作电压时，将所述DC/DC变换器的第一直流侧与待接入直流电网相连，提升所述DC/DC变换器的传输功率至所述DC/DC变换器的额定传输功率。
上述方案中，所述利用MMC换流站的交流源为所述MMC换流站的第 一子模块充电，包括以下步骤：
对所有所述第一子模块进行闭锁充电；
根据所述第一子模块闭锁充电的状态，对所有所述MMC换流站的第一子模块进行解锁充电。
上述方案中，所述对所有所述第一子模块进行闭锁充电，包括以下步骤：
将所有所述第一子模块的状态设置为闭锁状态；
采用不控充电方法(如交流系统通过二极管)对所述第一子模块进行充电，提升所述MMC换流站直流侧的电压至所述交流源的线电压峰值。
上述方案中，所述根据所述第一子模块闭锁充电的状态，对所有所述MMC换流站的第一子模块进行解锁充电，包括以下步骤：
判断所述MMC换流站直流侧的电压是否达到所述交流源的线电压峰值；
在判断结果为是的情况下，将所有所述第一子模块的状态设置为解锁状态；
采用定直流电压和定无功功率控制方法对所述第一子模块进行充电，提升所述MMC换流站直流侧的电压至所述MMC换流站的额定工作电压。
上述方案中，所述利用充电后的所述MMC换流站为DC/DC变换器充电，包括以下步骤：
对所有所述DC/DC变换器的第二子模块进行解锁充电，建立所述DC/DC变换器中的交流电压；
根据所述DC/DC变换器中的交流电压，对所述DC/DC变换器的第三子模块进行解锁充电。
上述方案中，所述对所有所述DC/DC变换器的第二子模块进行解锁充电，建立所述DC/DC变换器中的交流电压，包括：采用定交流电压和/或定 频率的控制方法以及调整所述第二子模块的投入数量，建立所述DC/DC变换器中的交流电压。
上述方案中，所述根据DC/DC变换器中的交流电压，对所述DC/DC变换器的第三子模块进行解锁充电，包括以下步骤：
采用所述交流电压对所述DC/DC变换器的第三子模块进行不控充电；
判断所述DC/DC变换器的第一直流侧的电压是否达到所述交流源的线电压峰值；
在判断结果为是的情况下，将所有所述第三子模块的状态设置为解锁状态；
采用定直流电压和定无功功率控制方法对所述第三子模块进行充电，提升所述DC/DC变换器的第一直流侧的电压至所述DC/DC变换器的额定工作电压。
上述方案中，所述控制所述DC/DC变换器的传输功率，使得所述DC/DC变换器的传输功率提升至所述DC/DC变换器的额定传输功率，包括：采用定有功功率和无功功率的方法控制所述DC/DC变换器的传输功率。
上述方案中，所述利用MMC换流站的交流源为所述MMC换流站的第一子模块充电的步骤之前，还包括：初始化所述MMC换流站以及所述DC/DC变换器的步骤。
本发明实施例还提供了一种换流站接入直流电网的控制装置，包括：
第一充电模块，配置为利用MMC换流站的交流源为所述MMC换流站的第一子模块充电；
第一判断模块，配置为判断所有所述第一子模块的电容电压是否提升至所述第一子模块的额定工作电压；
第二充电模块，配置为当所有所述第一子模块的电容电压提升至所述第一子模块的额定工作电压时，利用充电后的所述MMC换流站为DC/DC 变换器充电；
第二判断模块，配置为判断所有所述DC/DC变换器的子模块的电容电压是否提升至所述DC/DC变换器的子模块的额定工作电压；
组网模块，配置为当所有所述DC/DC变换器的子模块的电容电压提升至所述DC/DC变换器的子模块的额定工作电压时，将所述DC/DC变换器的第一直流侧与所述待接入直流电网相连，提升所述DC/DC变换器传输功率至所述DC/DC变换器的额定传输功率。
上述方案中，第一充电模块，包括：
第一充电子模块，配置为对所有所述第一子模块进行闭锁充电；
第一判断子模块，配置为判断所述MMC换流站直流侧的电压是否达到所述交流源的线电压峰值；
第一设置模块，配置为在判断结果为是的情况下，将所有所述第一子模块的状态设置为解锁状态；
第二充电子模块，配置为采用定直流电压和定无功功率控制方法对所述第一子模块进行充电，提升所述MMC换流站直流侧的电压至所述MMC换流站的额定工作电压。
上述方案中，第二充电模块，包括：
第三充电子模块，配置为对所有所述DC/DC变换器的第二子模块进行解锁充电，建立所述DC/DC变换器中的交流电压；
第四充电子模块，配置为采用所述交流电压对所述DC/DC变换器的第三子模块进行不控充电；
第二判断子模块，配置为判断所述DC/DC变换器的第一直流侧的电压是否达到所述交流源的线电压峰值；
第二设置模块，配置为在判断结果为是的情况下，将所有所述第三子模块的状态设置为解锁状态；
第五充电子模块，配置为采用定直流电压和定无功功率控制方法对所述第三子模块进行充电，提升所述DC/DC变换器的第一直流侧的电压至所述DC/DC变换器的额定工作电压。
上述方案中，所述控制装置，还包括：
初始化模块，配置为初始化所述MMC换流站以及所述DC/DC变换器。
本发明实施例还提供了一种控制器，包括至少一个处理器；以及与所述至少一个处理器通信连接的存储器；其中，所述存储器存储有可被所述一个处理器执行的指令，所述指令被所述至少一个处理器执行，以使所述至少一个处理器执行本发明实施例中的所述换流站接入直流电网的控制方法。
应用本发明实施例提供的技术方案，具有如下有益技术效果：
1.本发明实施例提供的MMC换流站接入直流电网的控制方法，包括以下步骤：利用MMC换流站的交流源为所述MMC换流站的第一子模块充电；判断所有所述第一子模块的电容电压是否提升至所述第一子模块的额定工作电压；当所有所述第一子模块的电容电压提升至所述第一子模块的额定工作电压时，利用充电后的所述MMC换流站为DC/DC变换器充电；判断所有所述DC/DC变换器的子模块的电容电压是否提升至所述DC/DC变换器的子模块的额定工作电压；当所有所述DC/DC变换器的子模块的电容电压提升至所述DC/DC变换器的子模块的额定工作电压时，将所述DC/DC变换器的第一直流侧与所述待接入直流电网相连，控制所述DC/DC变换器的传输功率，使得所述传输功率提升至所述DC/DC变换器的额定传输功率。本发明实施例采用的MMC换流站和DC/DC变换器的有序充电控制，能够有效降低MMC换流站接入直流电网的冲击电流，从而易于实现MMC换流站平滑接入直流电网，工程实践性强。
2.本发明实施例提供的MMC换流站接入直流电网的控制方法，其中 所述利用MMC换流站的交流源为要接入的MMC换流站(孤立MMC换流站)的第一子模块充电，包括以下步骤：对所有所述第一子模块进行闭锁充电；根据所述第一子模块闭锁充电的状态，对所有所述MMC换流站的第一子模块进行解锁充电。本发明实施例，通过对MMC换流站中第一子模块的电压的有序控制，能够有效降低MMC换流站的交流源对第一子模块充电时产生的冲击电流，易于实现MMC换流站的交流源对第一子模块的平稳充电，进而提高第一子模块的使用寿命。
3.本发明实施例提供的MMC换流站接入直流电网的控制方法，其中，所述利用充电后的所述MMC换流站为DC/DC变换器充电，包括以下步骤：对所有所述DC/DC变换器的第二子模块进行解锁充电，建立所述DC/DC变换器中的交流电压；根据所述DC/DC变换器中的交流电压，对所述DC/DC变换器的第三子模块进行解锁充电。本发明实施例中，通过对DC/DC变换器中各子模块的有序充电，能够降低MMC换流站接入DC/DC变换器时的冲击电流，易于实现MMC换流站平滑接入DC/DC变换器。
4.本发明实施例提供的一种MMC换流站接入直流电网的控制装置，包括：第一充电模块，配置为利用MMC换流站的交流源为所述MMC换流站的第一子模块充电；第一判断模块，配置为判断所有所述第一子模块的电容电压是否提升至所述第一子模块的额定工作电压；第二充电模块，配置为当所有所述第一子模块的电容电压提升至所述第一子模块的额定工作电压时，利用充电后的所述MMC换流站为DC/DC变换器充电；第二判断模块，配置为判断所有所述DC/DC变换器的子模块的电容电压是否提升至所述DC/DC变换器的子模块的额定工作电压；组网模块，配置为当所有所述DC/DC变换器的子模块的电容电压提升至所述DC/DC变换器的子模块的额定工作电压时，将所述DC/DC变换器的第一直流侧与所述待接入直流电网相连，提升所述DC/DC变换器传输功率至所述DC/DC变换器的额定 传输功率。本发明实施例采用的MMC换流站和DC/DC变换器的有序充电控制，能够有效降低MMC换流站接入直流电网的冲击电流，从而易于实现MMC换流站平滑接入直流电网，工程实践性强。
附图说明
图1为本发明实施例提供的MMC的基本结构示意图；
图2为本发明实施例提供的DC/DC变换器的一个拓扑示意图；
图3为本发明实施例提供的半H桥构成的MMC的子模块的结构示意图；
图4为本发明实施例提供的MMC中的子模块工作状态示意图；
图5为本发明实施例提供的直流电网的拓扑示意图；
图6为本发明实施例提供的MMC换流站接入直流电网的控制方法的流程示意图一；
图7为本发明实施例提供的MMC换流站接入直流电网的控制方法的流程示意图二；
图8为本发明实施例提供的MMC换流站接入直流电网的控制方法的流程示意图三；
图9为本发明实施例提供的MMC换流站接入直流电网的控制装置的组成结构示意图一；
图10为本发明实施例提供的MMC换流站接入直流电网的控制装置的组成结构示意图二；
图11为本发明实施例提供的控制器的组成结构示意图。
具体实施方式
为使本发明实施例的目的、技术方案和优点更加清楚，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描 述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
由于MMC换流站在直流电网中的接入点的电压等级可能与MMC换流站的直流电压等级不同，因此，可通过高电压大容量DC/DC变换器实现不同电压等级的孤立MMC换流站与直流电网的互连。其中，DC/DC变换器为基于MMC的传统半桥式DC/DC变换器，结构如图2所示，包括由变压器连接的两组MMC，两组MMC的交流侧通过变压器连接，其对应的直流侧分别为与待接入直流电网相连的第一直流侧以及与MMC换流站直流侧相连的第二直流侧。其中，将MMC换流站中的子模块称之为第一子模块；将DC/DC变换器中的子模块分为：与MMC换流站直流侧相连的一组MMC中的子模块称之为第二子模块，将DC/DC变换器与直流电网相连的一组MMC中的子模块称之为第三子模块。
如图1所示，MMC的每个桥臂由N个SM和一个桥臂电抗器串联而成。其中，SM的结构主要有半H桥结构和H桥结构以及双钳位型子模块结构。本发明实施例中的SM结构选自但不限于半H桥结构，图3示出了半H桥构成的MMC的子模块的结构示意图，如图3所示，半H桥构成的子模块主要由两个全控型高频开关IGBT1、IGBT2，分别与高频开关反并联的二极管VD1、VD2，以及子模块储能电容C组成。
图4示出了MMC中的子模块工作状态，如图4所示，根据子模块两个高频开关管的开关状态以及子模块的电流方向，可将子模块的工作形式分为3种状态，6种模式。当IGBT1和IGBT2都给定关断信号时，子模块处于闭锁状态；当IGBT1给定导通信号且IGBT2给定关断信号时，子模块处于解锁状态；当IGBT2给定导通信号且IGBT1给定关断信号时，子模块处于切除状态。
SM的3种状态6种模式的参数如表1所示，其中，将给定IGBT导通信号记为1，给定IGBT关断信号记为0；将IGBT的实际导通状态记为1，将IGBT的实际关断状态记为0；将VD的导通状态记为1，将VD的关断状态记为0；子模块的储能电容上的电压记为Uc。
表1SM的3种状态和6种模式
Figure PCTCN2018094236-appb-000001
Figure PCTCN2018094236-appb-000002
由表1内容可知，当SM处于稳态时，IGBT1、IGBT2、VD1、VD2四个元件中，每个子模块中有且仅有一个元件为导通状态，其他三个均为关断状态。当SM处于解锁状态时，无论电流如何流动，SM输出电压均为Uc，当SM处于切除状态时，无论电流如何流动，SM输出电压为0；即无论SM处于何种工作状态或工作模式，其输出电压要么为Uc，要么为0。闭锁状态下的模式1仅在MMC启动时向子模块电容器充电的时候出现，而闭锁状态下的模式2是在故障时将子模块电容器旁路的情况下使用。由上可知，只要对SM中的两个IGBT进行控制，SM便可在不同的模式下工作，实现SM的解锁和切除。
对于如图1所示的三相MMC而言，其三个相单元是并联连接的，每个相单元的工作原理均相同。三相MMC在正常稳态工作时，a、b、c三相中上下桥臂处于解锁状态的SM数之和均为N，即每相中SM总数的一半；由于三个相单元为并联连接，所以直流侧电压Udc等于每相桥臂电压，均为NUc；对于交流侧而言，虽然每相中处于解锁状态的SM总数固定不变，但是对上下桥臂中各SM的解锁和切除进行不同的分配，便可得到不同的 输出电压，因此可以通过对每相上下桥臂中的SM解锁切除状态进行合理控制来得到幅值和相位均满足要求的交流侧三相电压。
如图5所示，是本发明实施例的直流电网拓扑图，其既包含辐射状结构又包含环状结构。图5中的电压值为一个示例，本发明的保护范围并不限于此。其中MMC换流站为C1，其将要在线接入的直流电网为与DC/DC变换器的第一直流侧相连的直流电网。其中，MMC换流站为有源站；DC/DC变换器为基于MMC的传统半桥式DC/DC变换器，其与待接入直流电网相连的一端为DC1，与孤立MMC站直流侧相连的一端为DC2；DC2与孤立MMC站之间连接有若干直流断路器。
本发明施例提供一种MMC换流站接入直流电网的控制方法，可用于控制器中。如图6所示，该控制方法包括以下步骤：
步骤S11，利用MMC换流站的交流源为MMC换流站的第一子模块充电。
如图5所示，本实施例中，MMC换流站包括交流电压源G1，该电压源与MMC的交流侧电连接，因此，可利用G1为MMC换流站的第一子模块充电，即利用G1为MMC换流站的第一子模块中的电容充电，使得第一子模块中的电容电压升高。
步骤S12，判断所有第一子模块的电容电压是否提升至第一子模块的额定工作电压；在判断结果为是的情况下，执行步骤S13；否则，执行其他操作。
本实施例中，MMC子模块选定之后，其额定工作电压亦确定，将该额定工作电压存储在控制器中，以便于后续比较。
本实施例中，可以利用控制器对第一子模块的电容电压进行实时测量，并将该测量结果与预先存储的MMC子模块的额定工电压进行判断，从而判断第一子模块的电容电压是否已经达到第一子模块的额定工作电压。
此外，本实施例中的其他操作可以是利用控制器对第一子模块的电容电压进行循环测量，也可以是间隔一段时间利用控制器对第一子模块的电容电压进行测量。
步骤S13，利用充电后的MMC换流站为DC/DC变换器充电。
本实施例中，在所有第一子模块的电容电压已经提升至第一子模块的额定工作电压时，表示所有第一子模块已经充电完成。此时，利用充电后的MMC换流站为DC/DC变换器充电，以提升DC/DC变换器的电压。
步骤S14，判断所有DC/DC变换器的子模块的电容电压是否提升至DC/DC变换器的子模块的额定工作电压；在判断结果为是的情况下，执行步骤S15；否则继续对DC/DC变换器充电，直至所有DC/DC变换器的子模块的电容电压提升至DC/DC变换器的子模块的额定工作电压。
如图2所示，本实施例中的DC/DC变换器，包括通过变压器连接的两组MMC，其中每组MMC的三个桥臂上包括若干子模块。本实施例中，DC/DC变换器中的子模块结构与MMC换流站中的子模块结构相同，即选自但不限于半H桥结构。
本实施例中，DC/DC变换器子模块选定之后，其额定工作电压亦确定，将该额定工作电压存储在控制器中，以便于后续比较。
本实施例中，可以利用控制器对DC/DC变换器子模块的电容电压进行实时测量，并将该测量结果与预先存储的DC/DC变换器子模块的额定工电压进行判断，从而判断DC/DC变换器子模块的电容电压是否已经达到DC/DC变换器子模块的额定工作电压。
此外，本实施例中的其他操作可以是利用控制器对DC/DC变换器子模块的电容电压进行循环测量，也可以是间隔一段时间利用控制器对DC/DC变换器子模块的电容电压进行测量。
步骤S15，将DC/DC变换器的第一直流侧与待接入直流电网相连，提 升DC/DC变换器的传输功率至DC/DC变换器的额定传输功率。
本实施例中，在所有DC/DC变换器的子模块的电容电压提升至DC/DC变换器的子模块的额定工作电压时，表示DC/DC变换器的子模块已经充电完成。此时，通过控制器将DC/DC变换器的第一直流侧与待接入直流电网相连，并控制DC/DC变换器的传输功率，使得传输功率提升至DC/DC变换器的额定传输功率。本实施例中，DC/DC变换器的额定传输功率是预先存储在控制器中的。
本实施例采用MMC换流站和DC/DC变换器的有序充电控制，能够有效降低MMC换流站接入直流电网的冲击电流，从而易于实现MMC换流站平滑接入直流电网，工程实践性强。
本发明施例还提供一种MMC换流站接入直流电网的控制方法，用于控制器中。如图7所示，该控制方法包括以下步骤：
步骤S21，利用MMC换流站的交流源为MMC换流站的第一子模块充电。
在一实施例中，步骤S21包括以下步骤：
步骤S211，对所有第一子模块进行闭锁充电。
本实施例中，通过MMC换流站的交流源对MMC换流站的第一子模块进行闭锁充电，使得第一子模块的电容电压提升，即提升第一子模块的电压，进而提升MMC换流站直流侧的电压。
步骤S212，根据第一子模块闭锁充电的状态，对所有MMC换流站的第一子模块进行解锁充电。
本实施例中，可以在控制器中设置第一子模块在闭锁充电时，MMC换流站直流侧的电压达到第一预设电压时，将第一子模块的状态变换为解锁充电。其中，第一预设电压可以是MMC换流站的线电压峰值，也可以是MMC换流站的相电压峰值。
步骤S22，判断所有第一子模块的电容电压是否提升至第一子模块的额定工作电压。在判断结果为是的情况下，执行步骤S23；否则，执行其他操作。与实施例1中的步骤S12相同，不再赘述。
步骤S23，利用充电后的MMC换流站为DC/DC变换器充电。
本实施例中，利用充电后的MMC换流站为DC/DC变换器充电，包括以下步骤：
步骤S231，对所有DC/DC变换器的第二子模块进行解锁充电，建立DC/DC变换器中的交流电压。
本实施例中，通过控制器将DC/DC变换器的第二子模块的状态设置为解锁状态。在解锁的同时，增大与MMC换流站连接的一组MMC中上、下桥臂投入的子模块的数量，以匹配MMC换流站的直流侧电压，随后逐步减小与MMC换流站连接的一组MMC中上、下桥臂投入的子模块的数量，直至该数值达到与MMC换流站连接的一组MMC中上、下桥臂投入的子模块总数的额定值，通过先增大后减小上、下桥臂投入的子模块的数量的方法，可以减小解锁瞬间的MMC换流站对第二子模块的电流冲击。
此外，DC/DC变换器的第二直流侧与MMC换流站电连接，即利用充电后的MMC换流站为DC/DC变换器的第二子模块进行解锁充电，从而逐步建立DC/DC变换器中的交流电压。
作为本实施例的一种可选实施方式，采用定交流电压的控制方法，建立DC/DC变换器中的交流电压。即在控制器预先设定利用充电后的MMC换流站为DC/DC变换器的第二子模块进行解锁充电的方式为定交流电压控制。
步骤S232，根据DC/DC变换器中的交流电压，对DC/DC变换器的第三子模块进行解锁充电。
本实施例中，DC/DC变换器的两组MMC通过变压器电连接，在充电 后的MMC换流站为DC/DC变换器的第二子模块进行解锁充电的过程中，变压器两端的交流电压逐步建立。在该交流电压建立的过程中，对DC/DC变换器的第三子模块进行解锁充电，以提升DC/DC变换器的第一直流侧的电压。
步骤S24，判断所有DC/DC变换器的子模块的电容电压是否提升至DC/DC变换器的子模块的额定工作电压；在判断结果为是的情况下，执行步骤S25；否则，执行其他操作。
步骤S25，将DC/DC变换器的第一直流侧与待接入直流电网相连，提升DC/DC变换器的传输功率至DC/DC变换器的额定传输功率。
作为本实施例的一种可选实施方式，采用定有功功率和无功功率的控制方法，提升DC/DC变换器的传输功率。即在控制器预先设定提升DC/DC变换器的传输功率的方式为定有功功率和无功功率控制。
本发明施例还提供一种MMC换流站接入直流电网的控制方法，用于控制器中。如图8所示，该控制方法包括以下步骤：
步骤S30，初始化MMC换流站以及DC/DC变换器。
本实施例中，通过控制器将MMC换流站以及DC/DC变换器中各子模块的状态设置为闭锁状态，此外，将连接MMC换流站以及DC/DC变换器的电路中的直流断路器的状态设置为闭合，从而保证MMC换流站以及DC/DC变换器处于电连接状态。
步骤S31，利用MMC换流站的交流源为MMC换流站的第一子模块充电。
在一实施例中，步骤S31包括以下步骤：
步骤S311，采用不控充电方法对第一子模块进行充电，提升MMC换流站直流侧的电压至交流源的线电压峰值。
本实施例中，在MMC换流站的交流源为MMC换流站的第一子模块充 电之前，第一子模块为闭锁状态，即第一子模块中只有VD1和VD2处于工作状态，而VD1和VD2为不可控元件，即在MMC换流站的交流源刚开始为第一子模块时为不控充电方法。采用MMC换流站的交流源为第一子模块进行充电，以提升MMC换流站直流侧的电压。
步骤S312，判断MMC换流站直流侧的电压是否达到交流源的线电压峰值。在判断结果为是的情况下，执行步骤S313；否则，执行步骤S311。
本实施例中，MMC换流站的交流源的线电压峰值预先存储在控制器中。通过控制器实时测量MMC换流站直流侧的电压，并将测量结果与预先存储的交流源的线电压峰值进行比较，从而可以判断出MMC换流站直流侧的电压是否已达到交流源的线电压峰值。
步骤S313，将所有第一子模块的状态设置为解锁状态。
本实施例中，在MMC换流站直流侧的电压达到MMC换流站交流源的线电压峰值时，通过控制器将所有第一子模块的状态设置为解锁状态，以便于接着对第一子模块进行充电。
步骤S314，采用定直流电压和定无功功率控制方法对第一子模块进行充电，提升MMC换流站直流侧的电压至MMC换流站的额定工作电压。
本实施例中，采用定直流电压和定无功功率控制方法对设置为解锁状态的第一子模块进行充电，从而使得MMC换流站直流侧的电压提升至MMC换流站的额定工作电压。即本实施例中，为解锁状态的第一子模块进行充电时，通过控制器设置此时的控制方法为定直流电压和定无功功率控制方法。
本实施例中，由于MMC换流站以及DC/DC变换器已处于电连接状态，因此在对MMC换流站的第一子模块充电的同时，DC/DC变换器中的第二子模块的电压也在同时提升，从而保证了DC/DC变换器中的第二子模块的电压的逐步提升。
步骤S32，判断所有第一子模块的电容电压是否提升至第一子模块的额定工作电压。在判断结果为是的情况下，执行步骤S33；否则，执行步骤S314。与实施例2中的步骤S22相同，不再赘述。
步骤S33，利用充电后的MMC换流站为DC/DC变换器充电。
本实施例中，在对MMC换流站的第一子模块充电的同时，DC/DC变换器中的第二子模块的电压已经有一定的提升。此时，利用充电后的MMC换流站为DC/DC变换器充电，即在DC/DC变换器中的子模块的现有电压的基础上，对该电压再次进行提升，从而避免了直接利用MMC换流站为DC/DC变换器充电，使得DC/DC变换器的电压从零开始逐步提升，进而降低了MMC换流站为DC/DC变换器充电时所产生的冲击电流，达到平滑充电的目的。
在一实施例中，步骤S33包括以下步骤：
步骤S331，对所有DC/DC变换器的第二子模块进行解锁充电，建立DC/DC变换器中的交流电压。与实施例2中的步骤S231相同，不再赘述。
步骤S332，采用交流电压对DC/DC变换器的第三子模块进行不控充电。
由于，此时第三子模块处于闭锁状态，第三子模块的电路中只有二极管处于工作状态，而二极管为不可控元件，即采用交流电压对DC/DC变换器的第三子模块进行充电的方法为不控充电。
步骤S333，判断DC/DC变换器的第一直流侧的电压是否达到交流源的线电压峰值。在判断结果为是的情况下，执行步骤S334；否则，执行步骤S332。
本实施例中，通过控制器实时测量DC/DC变换器的第一直流侧的电压，并判断该电压与预先存储的MMC换流站的交流源的线电压峰值进行比较，从而可以得出该电压是否达到MMC换流站的交流源的线电压峰值。
步骤S334，将所有第三子模块的状态设置为解锁状态。
本实施例中，通过控制器将第三子模块的状态设置为解锁状态。
步骤S335，采用定直流电压和定无功功率控制方法对第三子模块进行充电，提升DC/DC变换器的第一直流侧的电压至DC/DC变换器的额定工作电压。
本实施例中，通过控制器设置对第三子模块进行充电的方法为定直流电压和定无功功率控制，从而将DC/DC变换器的第一直流侧的电压提升至DC/DC变换器的额定工作电压。
步骤S34，判断所有DC/DC变换器的子模块的电容电压是否提升至DC/DC变换器的子模块的额定工作电压。在判断结果为是的情况下，执行步骤S35；否则，执行步骤S33。与实施例2中的步骤S34相同，不再赘述。
步骤S35，将DC/DC变换器的第一直流侧与待接入直流电网相连，提升DC/DC变换器的传输功率至DC/DC变换器的额定传输功率。
本施例提供一种MMC换流站接入直流电网的控制装置，如图9所示，包括：
第一充电模块41，配置为利用MMC换流站的交流源为MMC换流站的第一子模块充电。
第一判断模块42，配置为判断所有第一子模块的电容电压是否提升至第一子模块的额定工作电压。
第二充电模块43，配置为当所有所述第一子模块的电容电压提升至第一子模块的额定工作电压时，利用充电后的MMC换流站为DC/DC变换器充电。
第二判断模块44，配置为判断所有DC/DC变换器的子模块的电容电压是否提升至DC/DC变换器的子模块的额定工作电压。
组网模块45，配置为当所有DC/DC变换器的子模块的电容电压提升至 DC/DC变换器的子模块的额定工作电压时，将DC/DC变换器的第一直流侧与待接入直流电网相连，提升DC/DC变换器传输功率至DC/DC变换器的额定传输功率。
本发明实施例采用的MMC换流站和DC/DC变换器的有序充电控制，能够有效降低MMC换流站接入直流电网的冲击电流，从而易于实现MMC换流站平滑接入直流电网，工程实践性强。
作为本实施例的一种可选方式，如图10所示，第一充电模块41，包括：
第一充电子模块411，配置为对所有第一子模块进行闭锁充电。
第一判断子模块412，配置为判断MMC换流站直流侧的电压是否达到交流源的线电压峰值。
第一设置模块413，配置为在判断结果为是的情况下，将所有第一子模块的状态设置为解锁状态。
第二充电子模块414，配置为采用定直流电压和定无功功率控制方法对第一子模块进行充电，提升孤立MMC换流站直流侧的电压至孤立MMC换流站的额定工作电压。
作为本实施例的一种可选方式，如图10所示，第二充电模块43，包括：
第三充电子模块431，配置为对所有DC/DC变换器的第二子模块进行解锁充电，建立DC/DC变换器中的交流电压。
第四充电子模块432，配置为采用交流电压对DC/DC变换器的第三子模块进行不控充电。
第二判断子模块433，配置为判断DC/DC变换器的第一直流侧的电压是否达到交流源的线电压峰值。
第二设置模块434，配置为在判断结果为是的情况下，将所有第三子模块的状态设置为解锁状态。
第五充电子模块435，配置为采用定直流电压和定无功功率控制方法对 第三子模块进行充电，提升DC/DC变换器的第一直流侧的电压至DC/DC变换器的额定工作电压。
作为本实施例的一种可选方式，如图10所示，MMC换流站接入直流电网的控制装置，还包括：
初始化模块40，配置为初始化MMC换流站以及DC/DC变换器。
本施例提供一种控制器，配置为执行本发明实施例的MMC换流站接入直流电网的控制方法。该控制器的硬件结构示意图，如图11所示，该控制器包括一个或多个处理器51以及存储器52，图11中以一个处理器51为例。其中，处理器51和存储器52可以通过总线或者其他方式连接，图11中以通过总线连接为例。
处理器51可以为中央处理器(Central Processing Unit，CPU)。处理器51还可以为其他通用处理器、数字信号处理器(Digital Signal Processor，DSP)、专用集成电路(Application Specific Integrated Circuit，ASIC)、现场可编程门阵列(Field-Programmable Gate Array，FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件等芯片，或者上述各类芯片的组合。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。
存储器52作为一种非暂态计算机可读存储介质，可用于存储非暂态软件程序、非暂态计算机可执行程序以及模块，如本发明实施例中的MMC换流站接入直流电网的控制方法对应的程序指令/模块。处理器51通过运行存储在存储器52中的非暂态软件程序、指令以及模块，从而执行服务器的各种功能应用以及数据处理，即实现上述实施例中的MMC换流站接入直流电网的控制方法。
存储器52可以包括存储程序区和存储数据区，其中，存储程序区可存储操作系统、至少一个功能所需要的应用程序；存储数据区可存储预先设 置的MMC换流站的第一子模块的额定工作电压、MMC换流站交流源的线电压峰值、DC/DC变换器的子模块的额定工作电压以及DC/DC变换器的的额定传输功率等。此外，存储器52可以包括高速随机存取存储器，还可以包括非暂态存储器，例如至少一个磁盘存储器件、闪存器件、或其他非暂态固态存储器件。在一些实施例中，存储器52可选包括相对于处理器51远程设置的存储器，这些远程存储器可以通过网络连接至待接入直流电网的控制系统。上述网络的实例包括但不限于互联网、企业内部网、局域网、移动通信网及其组合。
所述一个或者多个模块存储在所述存储器52中，当被所述一个或者多个处理器51执行时，执行本发明实施例中的MMC换流站接入直流电网的控制方法。
本发明实施例还提供了一种非暂态计算机存储介质，所述计算机存储介质存储有计算机可执行指令，该计算机可执行指令可执行本发明实施例所述的MMC换流站接入直流电网的控制方法。其中，所述存储介质可为磁碟、光盘、只读存储记忆体(Read-Only Memory，ROM)、随机存储记忆体(Random Access Memory，RAM)、快闪存储器(Flash Memory)、硬盘(Hard Disk Drive，HDD)或固态硬盘(Solid-State Drive，SSD)等；所述存储介质还可以包括上述种类的存储器的组合。
本领域技术人员可以理解，实现上述实施例方法中的全部或部分流程，是可以通过计算机程序来指令相关的硬件来完成，所述的程序可存储于一计算机可读取存储介质中，该程序在执行时，可包括如上述各方法的实施例的流程。其中，所述的存储介质可为磁碟、光盘、只读存储记忆体(ROM)或随机存储记忆体(RAM)等。
虽然结合附图描述了本发明的实施例，但是本领域技术人员可以在不脱离本发明的精神和范围的情况下作出各种修改和变型，这样的修改和变 型均落入由所附权利要求所限定的范围之内。

Claims (11)

  1. 一种换流站接入直流电网的控制方法，包括：
    利用模块化多电平换流器MMC换流站的交流源为所述MMC换流站的第一子模块充电；
    判断所有所述第一子模块的电容电压是否提升至所述第一子模块的额定工作电压；
    当所有所述第一子模块的电容电压提升至所述第一子模块的额定工作电压时，利用充电后的所述MMC换流站为DC/DC变换器充电；
    判断所有所述DC/DC变换器的子模块的电容电压是否提升至所述DC/DC变换器的子模块的额定工作电压；
    当所有所述DC/DC变换器的子模块的电容电压提升至所述DC/DC变换器的子模块的额定工作电压时，将所述DC/DC变换器的第一直流侧与所述待接入直流电网相连，提升所述DC/DC变换器传输功率至所述DC/DC变换器的额定传输功率。
  2. 根据权利要求1所述的控制方法，其中，所述利用MMC换流站的交流源为所述孤立MMC换流站的第一子模块充电，包括：
    对所有所述第一子模块进行闭锁充电；
    根据所述第一子模块闭锁充电的状态，对所有所述MMC换流站的第一子模块进行解锁充电。
  3. 根据权利要求2所述的控制方法，其中，所述对所有所述第一子模块进行闭锁充电，包括：
    采用不控充电方法对所述第一子模块进行充电，提升所述MMC换流站直流侧的电压至所述交流源的线电压峰值。
  4. 根据权利要求2所述的控制方法，其中，所述根据所述第一子模块闭锁充电的状态，对所有所述孤立MMC换流站的第一子模块进行解锁充 电，包括：
    判断所述MMC换流站直流侧的电压是否达到所述交流源的线电压峰值；
    在判断结果为是的情况下，将所有所述第一子模块的状态设置为解锁状态；
    采用定直流电压和定无功功率控制方法对所述第一子模块进行充电，提升所述孤立MMC换流站直流侧的电压至所述孤立MMC换流站的额定工作电压。
  5. 根据权利要求1所述的控制方法，其中，所述利用充电后的所述MMC换流站为DC/DC变换器充电，包括：
    对所有所述DC/DC变换器的第二子模块进行解锁充电，建立所述DC/DC变换器中的交流电压；
    根据所述DC/DC变换器中的交流电压，对所述DC/DC变换器的第三子模块进行解锁充电。
  6. 根据权利要求5所述的控制方法，其中，所述对所有所述DC/DC变换器的第二子模块进行解锁充电，建立所述DC/DC变换器中的交流电压，包括：采用定交流电压的控制方法以及调整所述第二子模块的投入数量，建立所述DC/DC变换器中的交流电压。
  7. 根据权利要求5所述的控制方法，其中，所述根据DC/DC变换器中的交流电压，对所述DC/DC变换器的第三子模块进行解锁充电，包括：
    采用所述交流电压对所述DC/DC变换器的第三子模块进行不控充电；
    判断所述DC/DC变换器的第一直流侧的电压是否达到所述交流源的线电压峰值；
    在判断结果为是的情况下，将所有所述第三子模块的状态设置为解锁状态；
    采用定直流电压和定无功功率控制方法对所述第三子模块进行充电，提升所述DC/DC变换器的第一直流侧的电压至所述DC/DC变换器的额定工作电压。
  8. 根据权利要求1所述的控制方法，其中，所述控制所述DC/DC变换器的传输功率，使得所述DC/DC变换器的传输功率提升至所述DC/DC变换器的额定传输功率，包括：采用定有功功率和无功功率的方法控制所述DC/DC变换器的传输功率。
  9. 根据权利要求1所述的控制方法，其中，所述利用MMC换流站的交流源为所述孤立MMC换流站的第一子模块充电的步骤之前，还包括：
    初始化所述MMC换流站以及所述DC/DC变换器。
  10. 一种控制器，包括至少一个处理器；以及与所述至少一个处理器通信连接的存储器；其中，所述存储器存储有可被所述一个处理器执行的指令，所述指令被所述至少一个处理器执行，以使所述至少一个处理器执行权利要求1-9中任一项所述的换流站接入直流电网的控制方法。
  11. 一种存储介质，所述存储介质包括存储的程序，其中，所述程序运行时执行权利要求1至9中任一项所述的换流站接入直流电网的控制方法。
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CN107634513A (zh) * 2017-08-21 2018-01-26 全球能源互联网研究院有限公司 Mmc换流站接入直流电网的控制方法及控制器

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CN105827106A (zh) * 2016-03-11 2016-08-03 广东明阳龙源电力电子有限公司 一种柔性直流输电系统中mmc零冲击启动并网方法
CN107634513A (zh) * 2017-08-21 2018-01-26 全球能源互联网研究院有限公司 Mmc换流站接入直流电网的控制方法及控制器

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