WO2021093746A1 - 混合直流换流器在线退出电路、退出方法及退出装置 - Google Patents

混合直流换流器在线退出电路、退出方法及退出装置 Download PDF

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Publication number
WO2021093746A1
WO2021093746A1 PCT/CN2020/127904 CN2020127904W WO2021093746A1 WO 2021093746 A1 WO2021093746 A1 WO 2021093746A1 CN 2020127904 W CN2020127904 W CN 2020127904W WO 2021093746 A1 WO2021093746 A1 WO 2021093746A1
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Prior art keywords
converter
switch
voltage source
valve group
bus
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PCT/CN2020/127904
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English (en)
French (fr)
Inventor
卢东斌
李海英
陈松林
陈乐�
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南京南瑞继保电气有限公司
南京南瑞继保工程技术有限公司
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Priority claimed from CN201911096356.9A external-priority patent/CN112787349B/zh
Priority claimed from CN201911095357.1A external-priority patent/CN112787347B/zh
Application filed by 南京南瑞继保电气有限公司, 南京南瑞继保工程技术有限公司 filed Critical 南京南瑞继保电气有限公司
Publication of WO2021093746A1 publication Critical patent/WO2021093746A1/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
    • 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

  • This application relates to the technical field of direct current transmission, in particular to an online exit circuit, exit method and exit device of a hybrid DC converter.
  • the advantage of current source HVDC transmission based on thyristor is that the converter loss is small, and the DC system can be restarted by phase shifting when a DC line failure occurs.
  • the disadvantage is that the inverter-side converter works in an active inverter and cannot be connected to a passive system. Commutation failures are likely to occur after disturbances occur when the inverter side is connected to the weak AC system. High reactive power consumption, high voltage and current harmonic content, it is necessary to install a filter device to provide reactive power and filtering.
  • the advantages of DC transmission based on voltage source converters are high controllability, can be connected to passive systems, and do not require reactive power compensation devices.
  • the disadvantage is that the converter has a large switching loss.
  • the modular multilevel converter with a half-bridge structure cannot control the fault current when the DC side fails. After the fault occurs, the fault can only be removed by opening the AC side circuit breaker.
  • ABB uses DC circuit breakers with additional DC lines to solve DC side failures.
  • Siemens uses a modular multilevel converter with a full-bridge circuit structure to solve the DC-side fault, but the converter with a full-bridge circuit structure has a large loss.
  • Alstom has adopted a full-bridge circuit and series-connected power electronic switching devices to solve the DC side failure, but the reliability has yet to be verified.
  • Zhejiang University uses a diode in series in the main circuit to solve the DC side failure, but the diode does not participate in the power conversion and will generate losses by itself.
  • NARI Relay Co., Ltd. proposes a hybrid DC converter with a bypass branch and a series connection of a voltage source converter.
  • the voltage source converter only needs to adopt a half-bridge circuit.
  • the modular multi-level converter is structured.
  • the grid-commutated converter can naturally block the DC side fault current, the bypass branch can reliably protect the voltage source converter, and the operation mode is more flexible.
  • the voltage source converter in the hybrid DC converter is a modular multilevel converter with a half-bridge circuit structure. The voltage adjustment range is limited. Unlike the grid commutated converter, the voltage cannot be adjusted to zero to achieve online exit.
  • the hybrid DC converter needs to be shut down or the DC current of the hybrid DC converter is temporarily controlled to be zero to separate the connection switch or switch of the voltage source converter To exit the operation.
  • the voltage source converter can be withdrawn online, the DC power will be interrupted during the withdrawal process. If the connection switch or switch fails during the withdrawal process, it is very likely to cause DC blocking and affect the smooth operation of the DC transmission system power.
  • the embodiment of the present application provides an online exit circuit for a hybrid DC converter.
  • the hybrid DC converter includes a current source type valve group unit and a voltage source type valve group unit connected in series, and the current source type valve group unit includes Power grid phase converter, the voltage source valve group unit includes a voltage source converter, wherein the online exit circuit includes a first valve group switch, a first bus switch, a first bypass switch, and a second valve Group switch or/and a second bus switch and a second bypass switch, the first valve group switch is used to connect the grid-commutation converter and the voltage source valve group unit; the first bus switch Used to connect the grid commutation converter and DC bus or neutral bus across the voltage source valve group unit, or used to connect the voltage source converter to the DC bus across the current source valve group unit A bus or a neutral bus; the first bypass switch is connected in parallel with the series circuit of the first valve group switch and the grid commutating converter; the second valve group switch is used to connect the voltage source The converter and the current source valve unit; the second bus switch is used
  • the voltage source valve group unit includes at least one of the voltage source converters connected in parallel.
  • the first busbar switch is used to connect the grid commutation converter and the DC bus, and the second busbar switch is used for To connect the voltage source converter and the DC bus; or the first bus switch is used to connect the voltage source converter to the neutral bus, and the second bus switch is used to connect the A voltage source converter and the DC bus.
  • the first busbar switch is used to connect the grid commutating converter and the neutral bus, and the second busbar switch is used for To connect the voltage source converter and the neutral bus; or the first bus switch is used to connect the voltage source converter to the DC bus, and the second bus switch is used to connect the A voltage source converter and the neutral bus.
  • the cathode of the current source valve unit is connected to the cathode of the voltage source valve unit.
  • the anode of the current source valve unit is connected to the anode of the voltage source valve unit.
  • the cathode of the current source valve unit is connected to the anode of the voltage source valve unit.
  • the anode of the current source type valve group unit is connected to the negative electrode of the voltage source type valve group unit.
  • the voltage source valve group unit further includes a current-limiting reactor, and the current-limiting reactor is connected in series with the voltage source converter.
  • the voltage source valve group unit further includes a fourth bypass switch connected in parallel with the series circuit of the current limiting reactor and the voltage source converter.
  • the current source valve group unit further includes a third bus switch.
  • the third bus switch is used to connect to the power grid for commutation.
  • the current source valve group unit is a high-end valve group, it is used to connect the power grid commutation converter and the DC bus.
  • the current source valve group unit further includes a third bypass switch for connecting the anode and the cathode of the grid-commutated converter.
  • the online exit circuit further includes a diode valve group connected in series with the parallel circuit of the first busbar switch or/and the first bypass switch or/and the third bypass switch;
  • the diode valve group is composed of multiple diodes connected in series.
  • the switch includes at least one of a mechanical switch, a switch, a DC circuit breaker, and a thyristor valve group.
  • the power grid commutation converter includes at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit, and the pulse bridge circuit includes a non-switchable semi-controlled power semiconductor device.
  • the voltage source converter includes a two-level converter, a diode clamped multilevel converter, a modular multilevel converter MMC, a hybrid multilevel converter HMC, At least one of a two-level cascaded converter CSL and a stacked two-level converter CTL, the converter including a fully controllable power semiconductor device that can be turned off.
  • the embodiment of the present application also provides an online exit method of a hybrid DC converter, which is applied to the online exit circuit of the hybrid DC converter described above, when the grid commutated converter and the voltage source converter are simultaneously When it is running and needs to exit the voltage source converter, the online exit method includes: closing the first bypass switch, blocking the grid commutating converter or controlling the phase shifting of the grid commutating converter; Switching, connecting the grid commutating converter and the voltage source converter in parallel; unlocking the grid commutating converter or removing the phase shift of the grid commutating converter, and transferring the DC power from the power grid.
  • the voltage source converter is transferred to the grid commutated converter; the voltage source converter is controlled to lock or the DC current of the voltage source converter is equal to or less than the minimum current; the voltage source converter is isolated Streamer.
  • the first bypass switch is closed to block the grid commutation converter or control the grid commutation Phase shifting of the power grid includes: closing the third bypass switch, blocking the power grid commutation converter or controlling the power grid commutation converter to shift phase, and the first busbar switch is used to cross the voltage When the source valve group unit is connected to the power grid commutating converter and the DC bus or the neutral bus, the first bypass switch is closed.
  • the DC voltage of the grid commutation converter is controlled to be zero or a smaller value.
  • the controlling the DC voltage of the power grid commutation converter to be zero or a smaller value includes: controlling the trigger angle of the power grid commutation converter to be between 85 degrees and 95 degrees to Control the DC voltage of the grid commutation converter to zero or a smaller value, typically 90 degrees; or/and control the grid commutation converter to control the input bypass pair to control the grid commutation
  • the DC voltage of the converter is a small value; the small value is greater than zero and less than 0.1 times the rated value of the DC voltage.
  • the controlling the phase shift of the power grid commutation converter includes: controlling the trigger angle of the power grid commutation converter to be between 120 degrees and 180 degrees to control the power grid commutation The inverter phase shifts.
  • the switching conversion when the first busbar switch is used to connect the grid commutation converter and a DC bus or a neutral bus across the voltage source valve group unit, the switching conversion includes: separating the The first valve group switch closes the first bus switch; when the first bus switch is used to connect the voltage source converter and the DC bus or the neutral bus across the current source valve group unit, The switch conversion includes: closing the first bus switch, separating the first bypass switch, separating the second valve group switch, and closing the second bypass switch.
  • the first bus bar switch is used to connect the grid-commutated converter to the direct current across the voltage source type valve group unit.
  • the method further includes: separating the third bypass switch; when the first bus switch is used to connect the current source valve group unit to the When the voltage source converter is connected to the DC bus or the neutral bus, before separating the first bypass switch, the method further includes: separating the third bypass switch.
  • the method when the first bus switch is used to connect the power grid commutation converter to a DC bus or a neutral bus across the voltage source valve group unit, both ends of the first bus switch are connected in parallel
  • the method further includes: turning on the auxiliary resistance; when the current flowing through the auxiliary resistance is zero or a very small value, then closing the first busbar switch; confirm After the first bus switch is closed, the auxiliary resistor is cut off; when the first bus switch is used to connect the voltage source converter and the DC bus or the neutral bus across the current source valve group unit,
  • the method further includes: turning on the auxiliary resistor; when the current flowing through the auxiliary resistor is zero or a very small value , Then close the second bypass switch; after determining that the second bypass switch is closed, cut off the auxiliary resistor.
  • the isolated voltage source converter when the first busbar switch is used to connect the grid commutation converter to a DC bus or a neutral bus across the voltage source valve group unit, includes : Separate the second valve group switch or/and the second bus switch; when the first bus switch is used to connect the voltage source converter and the DC bus or the middle across the current source valve group unit In the case of a sex bus, the isolated voltage source converter includes at least separating the first bus switch.
  • the embodiment of the present application also provides an online exit device for a hybrid DC converter, which is applied to the online exit circuit of the hybrid DC converter as described above.
  • the online exit device includes a detection unit and a control unit, and the detection unit detects the first DC voltage, the first DC current, and the first unlocking of the current source valve group unit.
  • the control unit Close the first bypass switch, block the power grid phase converter or control the phase shift of the power grid phase converter, and convert the grid phase converter to the voltage source through switch conversion
  • the converters are connected in parallel, unlock the grid commutated converter or cancel the phase shift of the grid commutated converter, transfer the DC power from the voltage source converter to the grid commutated converter, and control
  • the voltage source converter locks or controls the DC current of the voltage source converter to be equal to or less than the minimum current, and isolate the voltage source converter.
  • the technical solution provided by the embodiments of this application firstly locks the grid-commutated converter of the hybrid DC converter, connects the voltage source converter and the grid-commutated converter in parallel, unlocks the grid-commutated converter, and changes
  • the power of the voltage source converter is transferred to the grid commutator converter, the voltage source converter is controlled to lock, and the voltage source converter is isolated to realize the smooth online exit of the voltage source converter and ensure the stable operation of the DC transmission system power.
  • FIG. 1A is one of the topological structure diagrams of the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 1B is the second topological structure diagram of the connection between the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 1C is the third diagram of the topological structure of the connection between the current source valve unit and the voltage source valve unit in the hybrid DC converter of the present application.
  • Fig. 1D is the fourth diagram of the topological structure of the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 2 is an online exit circuit of a hybrid DC converter provided by an embodiment of the present application.
  • FIG. 3A is one of the specific structural diagrams of the connection between the current source type valve group unit and the voltage source type valve group unit in the hybrid DC converter of the present application.
  • Fig. 3B is the second specific structural diagram of the connection between the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 3C is the third specific structural diagram of the connection between the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 3D is the fourth specific structural diagram of the connection between the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 3E is the fifth specific structural diagram of the connection between the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 3F is the sixth specific structural diagram of the connection between the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 4 is a schematic flowchart of an online exit method for a hybrid DC converter provided by an embodiment of the present application.
  • Figure 5 is a high-voltage DC transmission device composed of four hybrid DC converter topologies of Figures 3A to 3D, and the low-end valve block adopts a current source valve block unit.
  • Figure 6 is a high-voltage DC transmission device composed of four hybrid DC converter topologies in Figures 3A to 3D, and the high-end valve block adopts a current source valve block unit.
  • Figure 7 is a high-voltage DC power transmission device that uses current source valve unit units on the rectifier side and the inverter side consists of two hybrid DC converters in Figure 3C and Figure 3D.
  • FIG. 8A is the seventh specific structural diagram of the connection between the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 8B is the eighth specific structural diagram of the connection between the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 8C is a ninth specific structural diagram of the connection between the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 8D is the tenth specific structural diagram of the connection between the current source type valve group unit and the voltage source type valve group unit in the hybrid DC converter of the present application.
  • Fig. 8E is the eleventh specific structure diagram of the connection between the current source valve group unit and the voltage source valve group unit in the hybrid DC converter of the present application.
  • Fig. 8F is a specific structural diagram 12 of the connection between the current source type valve group unit and the voltage source type valve group unit in the hybrid DC converter of the present application.
  • Figure 9 is a high-voltage direct current transmission device composed of four hybrid DC converter topologies in Figures 8A to 8D, and the low-end valve block adopts a voltage source valve block unit.
  • Figure 10 is a high-voltage DC transmission device composed of four hybrid DC converter topologies of Figures 8A to 8D, and the high-end valve block adopts a voltage source valve block unit.
  • Fig. 11 is a high-voltage direct current power transmission device composed of two hybrid direct current converters of Fig. 8C and Fig. 8D on the rectifier side using a current source valve group unit and the inverter side.
  • Fig. 12 is an online exit device of a hybrid DC converter provided by an embodiment of the present application.
  • Figures 1A to 1D show four topological structures in which a current source valve group unit and a voltage source valve group unit are connected in a hybrid DC converter provided by an embodiment of the present application.
  • the cathode X1 of the current source valve unit is connected to the cathode X4 of the voltage source valve unit.
  • the anode X2 of the current source valve unit is connected to the anode X3 of the voltage source valve unit.
  • the cathode X1 of the current source valve unit is connected to the anode X3 of the voltage source valve unit.
  • the anode X2 of the current source valve unit is connected to the cathode X4 of the voltage source valve unit.
  • Fig. 2 is an online exit circuit of a hybrid DC converter provided by an embodiment of the present application.
  • the hybrid DC converter includes a current source type valve group unit and a voltage source type valve group unit connected in series.
  • the current source type valve group unit includes a grid-commutated converter 1
  • the voltage source type valve group unit includes at least one voltage source converter 2 connected in parallel.
  • the power grid commutation converter 1 includes at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit.
  • the pulsating bridge circuit includes a non-switchable semi-controlled power semiconductor device, such as a thyristor.
  • Voltage source converter 2 includes two-level converter, diode clamped multi-level converter, modular multi-level converter MMC, hybrid multi-level converter HMC, two-level cascade type At least one of a converter CSL and a stacked two-level converter CTL.
  • the converter includes a fully controlled power semiconductor device that can be turned off, such as an IGBT.
  • the online exit circuit of the hybrid DC converter is used to exit the voltage source converter 2 online.
  • the online exit circuit of the hybrid DC converter includes a first valve group switch 5, a first bus switch 12, a first bypass switch 4, a second valve group switch 9 or/and a second bus switch 10, and a second bypass switch 8. .
  • the second valve group switch 9 and the second bus switch 10 are included at the same time.
  • the first valve group switch 5 is used to connect the grid-commutated converter 1 and the voltage source valve group unit.
  • the first bus switch 12 is used to connect the power grid commutating converter 1 and the DC bus or the neutral bus. In the embodiment of FIG. 2, the first bus switch 12 is used to connect the grid-commutated converter 1 and the DC bus across the voltage source valve group unit.
  • the first bypass switch 4 is connected in parallel with the series circuit of the first valve group switch 5 and the grid commutating converter 1.
  • the second valve group switch 9 is used to connect the voltage source converter 2 and the current source valve group unit.
  • the second bus switch 10 is used to connect the voltage source converter 2 to the DC bus or the neutral bus. In the embodiment of FIG. 2, the second bus switch 10 is used to connect the voltage source converter 2 and the DC bus.
  • the second bypass switch 8 is connected in parallel with the series circuit of the voltage source converter 2 and the second valve group switch 9 or/and the second bus switch 10.
  • the first busbar switch 12 in the circuit structure shown in Figures 2, 3A to 3F, Figure 4, Figure 5 and Figure 6 is used to connect the grid commutating converter 1 and the DC bus or the DC bus across the voltage source valve group unit. Neutral bus.
  • the cathode X1 of the current source valve unit is connected to the cathode X4 of the voltage source valve unit.
  • the anode X2 of the current source valve unit is connected to the anode X3 of the voltage source valve unit.
  • the cathode X1 of the current source valve unit is connected to the anode X3 of the voltage source valve unit.
  • the anode X2 of the current source valve unit is connected to the cathode X4 of the voltage source valve unit.
  • the cathode X1 of the current source valve unit is connected to the anode X3 of the voltage source valve unit.
  • the anode X2 of the current source valve unit is connected to the cathode X4 of the voltage source valve unit.
  • the first bus bar switch 12 when the current source valve group unit is a low-end valve group, the first bus bar switch 12 is used to connect the grid commutating converter 1 and the DC bus, and the second bus bar switch 10 is used to connect the voltage source Inverter 2 and DC bus.
  • the first bus bar switch 12 When the current source valve group unit is a high-end valve group, the first bus bar switch 12 is used to connect the grid phase converter 1 and the neutral bus, and the second bus switch 10 is used to connect the voltage source converter 2 and the neutral bus.
  • the series-connected circuit of the voltage source converter 2, the current-limiting reactor 11, the second valve group switch 9 or/and the second bus switch 10 is connected in parallel with the second bypass switch 8.
  • a current-limiting reactor 11 is provided.
  • the voltage source valve group unit further includes a fourth bypass switch 7, a circuit in which the current-limiting reactor 11 and the voltage source converter 2 are connected in series and the fourth bypass switch 7 Connect in parallel.
  • the current source valve group unit further includes a third bus switch 6 for connecting the power grid commutating converter 1 with a neutral bus or a DC bus.
  • the third bus switch 6 is used to connect the power grid inverter 1 and the neutral bus.
  • the third bus switch 6 is used to connect the power grid inverter 1 and the DC bus.
  • the current source type valve group unit further includes a third bypass switch 3 for connecting the anode and the cathode of the power grid inverter 1.
  • the online exit circuit of the hybrid DC converter further includes a diode valve group 36 connected in series with the parallel circuit of the first bypass switch 4 and the third bypass switch 3; the diode valve group 36 is composed of multiple diodes connected in series.
  • the various switches mentioned in the above embodiments include at least one of mechanical switches, knife switches, DC circuit breakers, and thyristor valve groups.
  • the thyristor valve group is composed of multiple thyristors in series.
  • the online withdrawal method of the hybrid DC converter includes the following procedures, as shown in FIG. 4.
  • the first bypass switch 4 is closed to block the grid commutating converter 1 or control the grid commutating converter 1 to shift phase.
  • the specific steps are: controlling the DC voltage of the commutating converter 1 of the power grid to be zero or a smaller value.
  • the current source valve group unit includes the third bypass switch 3, close the third bypass switch 3 to block the grid commutating converter 1 or control the phase shift of the grid commutating converter 1, and close the first bypass switch 4 ; If the current source valve group unit does not include the third bypass switch 3, close the first bypass switch 4, block the grid commutating converter 1 or control the grid commutating converter 1 to shift the phase.
  • the DC voltage of the above-mentioned control grid commutated converter 1 is zero or a smaller value.
  • the trigger angle of the control grid commutated converter 1 is between 85° and 95° to control the DC voltage of the grid commutated converter 1
  • the voltage is zero or less, and the typical value is 90 degrees.
  • the above-mentioned smaller value is greater than zero and less than 0.1 times the rated value of the DC voltage.
  • the above-mentioned phase shift of the control grid-commutated inverter 1 means that the trigger angle of the control grid-commutated inverter 1 is between 120 degrees and 180 degrees, with a typical value of 164 degrees.
  • the switching conversion includes: if the current source valve group unit includes the third bypass switch 3, separate the third bypass switch 3, separate the first valve group switch 5, and close the first bus switch 12; if the current source valve group unit does not The third bypass switch 3 is included, the first valve group switch 5 is separated, and the first bus switch 12 is closed. At this time, the grid-commutated converter 1 and the voltage source converter 2 are connected in parallel.
  • the auxiliary resistor Before closing the first busbar switch 12, in order to prevent the generation of a large closing current, if an auxiliary resistor is connected in parallel at both ends of the first busbar switch 12, the auxiliary resistor should be connected first. When the current flowing through the auxiliary resistor is zero or a very small value, then The first bus switch 12 is closed, and the auxiliary resistance is cut off after the first bus switch 12 is closed. The minimum current value is less than the current value of the closed current that the first busbar switch 12 can withstand.
  • the voltage source converter 2 is controlled to be blocked or the DC current of the voltage source converter 2 is controlled to be equal to or less than the minimum current.
  • the minimum current value is less than or equal to the breaking current value of the second valve group switch 9 or the second bus switch 10, and preferably, the minimum current value is zero.
  • Figure 5 is a high-voltage direct current transmission device composed of four hybrid DC converter topologies of Figures 3A to 3D, and the low-end valve block adopts current source valve block units. It shows that the high-voltage direct current transmission device is all composed of Figures 3A to 3D.
  • the four structural components shown in 3D, the current source valve group unit is an embodiment of the low-end valve group.
  • the rectifier station 27 and the inverter station 28 are connected through the DC line 15.
  • the rectifier station 27 is composed of the structure 23 in FIG. 3A and the structure 24 in FIG. 3B, respectively, to form a positive converter and a negative converter.
  • the inverter station 28 is composed of the structure 25 in FIG. 3C and the structure 26 in FIG. 3D, respectively, to form its negative inverter and positive inverter.
  • the grid-commutated converter 1 is connected to the secondary winding of a current source HVDC transmission transformer 18 based on a thyristor
  • the voltage source converter 2 is connected to the secondary winding of a HVDC transmission transformer 19 based on a voltage source converter.
  • the AC power grid is three-phase, but only one phase is shown in FIG. 5 for clarity.
  • the primary winding of the high-voltage direct current transmission transformer is switched to and closed with the AC power grid 22 by means of an AC switch 21.
  • the voltage source converter 2 is used to provide reactive power for the grid commutated converter 1, the AC filter is less or not configured.
  • a bridge arm reactor 20 is provided in order to suppress the bridge arm circulating current of the voltage source converter 2 and the surge current under fault.
  • a smoothing reactor 13 and a current-limiting reactor 11 are provided.
  • Fig. 5 shows a ground electrode wire 16 for connecting the converter to the ground electrode.
  • a DC filter 14 is arranged between the neutral bus 33 and the valve group connection line 17.
  • the first valve group switch 5 of the current source valve group unit is close to the side of the power grid commutating converter 1 and the first bus switch 12 is connected across the DC bus 29.
  • the online exit circuit of the hybrid DC converter is used to exit the voltage source converter 2 online.
  • the current source valve group unit in Figure 5 is a low-end valve group, and the converter online exit circuit includes at least the first valve group switch 5, the first bus switch 12, and the first bypass switch 4 of the current source valve group unit. ,
  • the first valve group switch 5 and the third bus switch 6 of the current source valve group unit are in the closed position, and the first bus switch 12, the third bus switch 12 and the third bus switch 6 are in the closed position.
  • the bypass switch 3 and the first bypass switch 4 are in the off position.
  • the second valve group switch 9 and the second bus switch 10 are in a closed position.
  • the fourth bypass switch 7 is in an off or separated state, and the second bypass switch 8 is in a divided position.
  • the voltage source converter 2 and the current-limiting reactor 11 A DC circuit breaker with breaking DC fault current is connected in series, or the first busbar switch 12 adopts a DC circuit breaker with breaking DC fault current, or the voltage source converter 2 of the hybrid DC converter of the inverter station 28 and the limiter are used.
  • a diode valve group is connected in series between the galvanic reactor 11 to block the reverse current of the voltage source converter 2.
  • the cathode of the diode valve group and the anode of the voltage source converter are the common connection or the anode of the diode valve group and the voltage source
  • the negative pole of the converter is the common connection end, or the hybrid DC converter of the inverter station 28 adopts the circuit structure of FIG. 3E and FIG. 3F. It should be pointed out that the reverse current of the voltage source converter 2 in the hybrid DC converter of the inverter station 28 flows from the negative electrode of the voltage source converter 2 to the positive electrode.
  • Figure 6 is a high-voltage direct current transmission device composed of four hybrid DC converter topologies of Figures 3A to 3D, and the high-end valve block adopts current source valve block units. It shows that the high-voltage direct current transmission device is all composed of Figure 3A to Figure 3D.
  • the four structural components shown, the current source type valve group unit is an embodiment of the high-end valve group.
  • the rectifier station 27 and the inverter station 28 are connected through the DC line 15.
  • the rectifier station 27 is composed of the structure 23 in FIG. 3A and the structure 24 in FIG. 3B, respectively, to form its negative converter and positive converter.
  • the inverter station 28 is composed of the structure 25 in FIG. 3C and the structure 26 in FIG. 3D, respectively, to form a positive inverter and a negative inverter.
  • the grid-commutated converter 1 is connected to the secondary winding of a current source high-voltage direct current transmission transformer 18 based on a thyristor.
  • the voltage source converter 2 is connected to the secondary winding of the high voltage direct current transmission transformer 19 based on the voltage source converter.
  • the AC power grid is three-phase, but only one phase is shown in FIG. 6 for clarity.
  • the primary winding of the high-voltage direct current transmission transformer is switched to and closed with the AC power grid 22 by means of an AC switch 21.
  • the AC filter is less or not configured.
  • a bridge arm reactor 20 is provided in order to suppress the bridge arm circulating current of the voltage source converter 2 and the surge current under fault.
  • a smoothing reactor 13 and a current-limiting reactor 11 are provided.
  • FIG. 6 shows that the ground electrode wire 16 is used for the connection between the inverter and the ground electrode.
  • a DC filter 14 is arranged between the DC bus 29 and the valve block connection line 17.
  • the first valve group switch 5 of the current source valve group unit is close to the side of the power grid commutating converter 1 and the first bus switch 12 is connected across the neutral bus 33.
  • the online exit circuit of the hybrid DC converter is used to exit the voltage source converter 2 online, and the current source valve group unit in Fig. 6 is a high-end valve group.
  • the converter online exit circuit includes at least the first valve group switch 5, the first busbar switch 12, the first bypass switch 4, the second valve group switch 9 or the second busbar switch 10 and the second busbar switch of the current source valve group unit.
  • the first valve group switch 5 and the third bus switch 6 of the current source valve group unit are in the closed position, and the first bus switch 12 and the third bus switch 6 are in the closed position.
  • the bypass switch 3 and the first bypass switch 4 are in the off position.
  • the second valve group switch 9 and the second bus switch 10 are in the closed position, the fourth bypass switch 7 is in the off or separated state, and the second bypass switch 8 is in the off position.
  • the voltage source converter 2 and the current-limiting reactor 11 A DC circuit breaker with breaking DC fault current is connected in series, or the first busbar switch 12 adopts a DC circuit breaker with breaking DC fault current, or the voltage source converter 2 of the hybrid DC converter of the inverter station 28 and the limiter are used.
  • a diode valve group is connected in series between the galvanic reactor 11 to block the reverse current of the voltage source converter 2.
  • the cathode of the diode valve group and the anode of the voltage source converter are the common connection or the anode of the diode valve group and the voltage source
  • the negative pole of the converter is the common connection end, or the hybrid DC converter of the inverter station 28 adopts the circuit structure of FIG. 3E and FIG. 3F. It should be pointed out that the reverse current of the voltage source converter 2 in the hybrid DC converter of the inverter station 28 flows from the negative electrode of the voltage source converter 2 to the positive electrode.
  • Figure 7 is a high-voltage direct current transmission device composed of a current source valve group unit on the rectifier side and two hybrid DC converters on the inverter side as shown in Figure 3C and Figure 3D, showing that the high-voltage direct current transmission device consists of a traditional current source valve
  • the rectifier station 27 of the high-voltage direct current transmission device is composed of a structure 30 in which current source valve unit units are connected in series.
  • the inverter station 28 is composed of the structure 25 in FIG. 3C and the structure 26 in FIG. 3D respectively.
  • the grid-commutated converter 1 is connected to the secondary winding of a current source HVDC transmission transformer 18 based on a thyristor, and the voltage source converter 2 is connected to the secondary winding of a HVDC transmission transformer 19 based on a voltage source converter.
  • the rectifier station 27 is equipped with an AC filter 32 to filter out harmonics and provide reactive power, and is separated and combined with the AC power grid 22 through an AC switch 31.
  • a bridge arm reactor 20 is provided in order to suppress the bridge arm circulating current of the voltage source converter and the surge current under fault.
  • a smoothing reactor 13 and a current-limiting reactor 11 are provided in order to smooth the DC voltage of the DC circuit and suppress the DC fault current.
  • FIG. 7 shows that the ground electrode wire 16 is used to connect the inverter to the ground electrode.
  • the rectifier station 27 arranges the DC filter 14 between the DC line 15 and the ground electrode conductor 16.
  • the inverter station 28 is provided with a DC filter 14 between the DC bus 29 and the valve group connection line 17.
  • the first valve group switch 5 of the current source valve group unit is close to the side of the power grid commutating converter 1 and the first bus switch 12 is connected across the neutral bus 33.
  • the online exit circuit of the hybrid DC converter is used to exit the voltage source converter 2 online.
  • the current source valve group unit in Fig. 7 is a high-end valve group, and the converter online exit circuit includes at least the first part of the current source valve group unit.
  • the first valve group switch 5 and the third bus switch 6 of the current source valve group unit are in the closed position, and the first bus switch 12, the third bus switch 12 and the third bus switch 6 are in the closed position.
  • the bypass switch 3 and the first bypass switch 4 are in the off position.
  • the second valve group switch 9 and the second bus switch 10 are in the closed position, the fourth bypass switch 7 is in the off or separated state, and the second bypass switch 8 is in the off position.
  • the voltage source converter 2 and the current-limiting reactor 11 A DC circuit breaker with breaking DC fault current is connected in series, or the first busbar switch 12 adopts a DC circuit breaker with breaking DC fault current, or the voltage source converter 2 of the hybrid DC converter of the inverter station 28 and the limiter are used.
  • a diode valve group is connected in series between the galvanic reactor 11 to block the reverse current of the voltage source converter 2.
  • the cathode of the diode valve group and the anode of the voltage source converter are the common connection or the anode of the diode valve group and the voltage source
  • the negative pole of the converter is the common connection end, or the hybrid DC converter of the inverter station 28 adopts the circuit structure of FIG. 3E and FIG. 3F. It should be pointed out that the reverse current of the voltage source converter 2 in the hybrid DC converter of the inverter station 28 flows from the negative electrode of the voltage source converter 2 to the positive electrode.
  • the first bus switch 12 in the circuit structures shown in FIGS. 8A to 8F, FIG. 9, FIG. 10, and FIG. 11 is used to connect the voltage source converter 2 and the DC bus or the neutral bus across the current source valve group unit.
  • the hybrid DC converter includes a current source type valve group unit and a voltage source type valve group unit connected in series.
  • the current source type valve group unit includes a grid-commutated converter 1
  • the voltage source type valve group unit includes at least one voltage source converter 2 connected in parallel.
  • the power grid commutation converter 1 includes at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit.
  • the pulsating bridge circuit includes a non-switchable semi-controlled power semiconductor device, such as a thyristor.
  • Voltage source converter 2 includes two-level converter, diode clamped multi-level converter, modular multi-level converter MMC, hybrid multi-level converter HMC, two-level cascade type At least one of a converter CSL and a stacked two-level converter CTL.
  • the converter includes a fully controlled power semiconductor device that can be turned off, such as an IGBT.
  • the first valve group switch 5 is used to connect the grid-commutated converter 1 and the voltage source valve group unit.
  • the third bus switch 6 is used to connect the power grid commutating converter 1 and the DC bus or the neutral bus.
  • the series circuit of the grid commutation converter 1 and the first valve group switch 5 or/and the third bus switch 6 is connected in parallel with the first bypass switch 4.
  • the second valve group switch 9 is used to connect the voltage source converter 2 and the current source valve group unit.
  • the second bus switch 10 is used to connect the voltage source converter 2 to the neutral bus or the DC bus.
  • the first bus switch 12 is used to connect the voltage source converter 2 to the DC bus or the neutral bus.
  • the series circuit of the voltage source converter 2 and the second valve group switch 9 or/and the second bus switch 10 is connected in parallel with the second bypass switch 8.
  • the third bypass switch 3 is used to connect the anode and the cathode of the grid-commutated converter 1.
  • the first bus switch 12 is used to connect the voltage source converter 2 to the DC bus
  • the second bus switch 10 is used to connect the voltage source converter 2 to the neutral. Busbar.
  • the first bus switch 12 is used to connect the voltage source converter 2 and the neutral bus
  • the second bus switch 10 is used to connect the voltage source converter 2 and the DC bus.
  • a current-limiting reactor 11 In order to suppress the DC fault current, a current-limiting reactor 11 is provided.
  • the fourth bypass switch 7 is used to connect the positive pole and the negative pole of the voltage source converter 2.
  • a diode valve group or a DC circuit breaker can be connected in series with the positive or negative pole of the voltage source converter 2.
  • the online exit circuit of the hybrid DC converter further includes a diode valve group 36, which is connected in series with the first bus switch and the parallel circuit of the first bypass switch and the third bypass switch; the diode valve group 36 Consists of multiple diodes connected in series.
  • the cathode X1 of the current source valve unit is connected to the cathode X4 of the voltage source valve unit.
  • the anode X2 of the current source valve unit is connected to the anode X3 of the voltage source valve unit.
  • the cathode X1 of the current source valve unit is connected to the anode X3 of the voltage source valve unit.
  • the anode X2 of the current source valve unit is connected to the cathode X4 of the voltage source valve unit.
  • the cathode X1 of the current source valve unit is connected to the anode X3 of the voltage source valve unit.
  • the anode X2 of the current source valve unit is connected to the cathode X4 of the voltage source valve unit.
  • the various switches mentioned in the above embodiments include at least one of mechanical switches, knife switches, DC circuit breakers, and thyristor valve groups.
  • the first valve group switch 5 and the second valve group switch 9 are in the closed position, and the first busbar switch 12, the first bypass switch 4, and the second valve group switch are in the closed position.
  • the second bypass switch 8 and the third bypass switch 3 are in the minute position. If the current source valve group unit includes the third bus switch 6, the third bus switch 6 is in the closed position. If the voltage source valve group unit includes the second bus switch 10, the second bus switch 10 is in the closed position. If the voltage source type valve group unit includes the fourth bypass switch 7, the fourth bypass switch 7 is in the off position.
  • the first bypass switch 4 is closed to block the grid commutating converter 1 or control the grid commutating converter 1 to shift phase.
  • the specific steps are: controlling the DC voltage of the commutating converter 1 of the power grid to be zero or a smaller value.
  • the current source valve group unit includes the third bypass switch 3, close the third bypass switch 3, block the grid commutating converter 1 or control the phase shift of the grid commutating converter 1, optionally, further close the second A bypass switch 4; if the current source valve group unit does not include the third bypass switch 3, close the first bypass switch 4 to block the grid commutating converter 1 or control the phase shifting of the grid commutating converter 1.
  • the switching conversion includes: closing the first bus switch 12 of the voltage source valve unit, separating the first bypass switch 4 of the current source valve unit, separating the second valve group switch 9, and closing the first bus switch of the voltage source valve unit.
  • the switching conversion includes: closing the first bus switch 12 of the voltage source valve unit, separating the third bypass switch 3 of the current source valve unit, and separating the first
  • the second valve group switch 9 closes the second bypass switch 8 of the voltage source valve group unit.
  • the voltage source converter 2 is connected in parallel with the grid commutated converter 1.
  • the switching conversion includes: closing the first bus switch 12 of the voltage source valve group unit, and separating the first bypass switch of the current source valve group unit.
  • the bypass switch 4 and the third bypass switch 3 separate the second valve group switch 9 and close the second bypass switch 8 of the voltage source valve group unit.
  • the voltage source converter 2 is connected in parallel with the grid commutated converter 1.
  • an auxiliary resistor is connected in parallel at both ends of the second bypass switch 8, and the auxiliary resistor is first connected.
  • the second bypass switch 8 is closed again, and the auxiliary resistance is cut off after confirming that the second bypass switch 8 is closed.
  • the minimum current value is less than the current value of the closed current that the second bypass switch 8 can withstand.
  • the voltage source converter 2 is controlled to be blocked or the DC current of the voltage source converter 2 is controlled to be equal to or less than the minimum current.
  • the minimum current value is less than or equal to the breaking current value of the first bus bar switch 12 or the second bus bar switch 10.
  • the voltage source valve group unit includes the second bus switch 10, when the first bus switch 12 is disconnected, the second bus switch 10 is simultaneously disconnected.
  • the second bus switch 10 is used to connect the voltage source converter 2 to the DC bus or the neutral bus.
  • Fig. 9 is an embodiment of a high-voltage direct current transmission device composed of four hybrid DC converter topologies of Figs. 8A to 8D, and the low-end valve group adopts a voltage source valve group unit.
  • the rectifier station 27 and the inverter station 28 are connected through the DC line 15.
  • the rectifier station 27 is composed of the topological structure 23 in FIG. 8A and the topological structure 24 in FIG. 8B respectively forming its negative converter and positive converter.
  • the inverter station 28 is composed of the topological structure 25 in FIG. 8C and the topological structure 26 in FIG. 8D, respectively, to form its positive converter and negative converter.
  • the grid-commutated converter 1 is connected to the secondary winding of a current source high-voltage direct current transmission transformer 18 based on a thyristor.
  • the voltage source converter 2 is connected to the secondary winding of the high voltage direct current transmission transformer 19 based on the voltage source converter.
  • the AC power grid is three-phase, but only one phase is shown in FIG. 4 for clarity.
  • the primary winding of the high-voltage direct current transmission transformer is switched to and closed with the AC power grid 22 by means of an AC switch 21.
  • the voltage source converter 2 is used to provide reactive power for the grid commutated converter 1, the AC filter is less or not configured.
  • a bridge arm reactor 20 is provided in order to suppress the bridge arm circulating current of the voltage source converter and the surge current under fault.
  • a smoothing reactor 13 and a current-limiting reactor 11 are provided.
  • Fig. 9 shows a ground electrode wire 16 for connecting the converter to the ground electrode.
  • a DC filter 14 is arranged between the DC bus 29 and the valve block connection line 17.
  • the second valve group switch 9 is close to the voltage source converter 2 side and the first bus switch 12 is connected across the DC bus.
  • the first bypass switch 4 When the grid commutation converter 1 and the voltage source converter 2 of the hybrid DC converter are running at the same time, the first bypass switch 4, the second bypass switch 8, the third bypass switch 3, and the fourth bypass switch The switch 7 is in the position, the first valve group switch 5, the second valve group switch 9, the second bus switch 10, and the third bus switch 6 are in the closed position, and the first bus switch 12 is in the position.
  • the voltage source converter 2 and the current-limiting reactor 11 A DC circuit breaker with breaking DC fault current is connected in series, or the first busbar switch 12 adopts a DC circuit breaker with breaking DC fault current, or the voltage source converter 2 of the hybrid DC converter of the inverter station 28 and the limiter are used.
  • a diode valve group is connected in series between the galvanic reactors 11 to block the reverse current of the voltage source converter 2.
  • the cathode of the diode valve group and the anode of the voltage source converter 2 are the common connection end, or a hybrid of the inverter station 28
  • the DC converter adopts the circuit structure of Fig. 8E and Fig. 8F. It should be pointed out that the reverse current of the voltage source converter 2 in the hybrid DC converter of the inverter station 28 flows from the negative electrode of the voltage source converter 2 to the positive electrode.
  • Figure 10 is a high-voltage direct current transmission device composed of four hybrid DC converter topologies, and the high-end valve group adopts a voltage source valve group unit. It shows that the high-voltage direct current transmission device is all composed of the four types shown in Figures 8A to 8D.
  • the structural composition and voltage source valve group unit is an embodiment of the high-end valve group.
  • the rectifier station 27 and the inverter station 28 are connected through the DC line 15.
  • the rectifier station 27 is composed of the topological structure 23 in FIG. 8A and the topological structure 24 in FIG. 8B respectively forming its positive converter and negative converter.
  • the inverter station 28 is composed of the topological structure 25 in FIG. 8C and the topological structure 26 in FIG. 8D, respectively, to form its negative converter and positive converter.
  • the grid-commutated converter 1 is connected to the secondary winding of a current source high-voltage direct current transmission transformer 18 based on a thyristor.
  • the voltage source converter 2 is connected to the secondary winding of the high voltage direct current transmission transformer 19 based on the voltage source converter.
  • the primary winding of the HVDC transformer is separated and combined with the AC power grid 22 by means of the AC switch 21. If the voltage source converter 2 is used to provide reactive power for the grid commutating converter 1, the AC filter will be less or not configured.
  • a bridge arm reactor 20 is provided in order to suppress the bridge arm circulating current of the voltage source converter and the surge current under fault.
  • a smoothing reactor 13 and a current-limiting reactor 11 are provided in order to smooth the DC voltage and suppress the DC fault current.
  • FIG. 10 shows a ground electrode wire 16 which is used to connect the inverter to the ground electrode.
  • a DC filter 14 is arranged between the neutral bus 33 and the valve group connection line 17.
  • the first busbar switch 12 is connected across the second valve group switch 9 between the side close to the voltage source converter 2 and the neutral busbar 33.
  • the first bypass switch 4 the second bypass switch 8, the third bypass switch 3, and the fourth bypass switch
  • the switch 7 is in the position
  • the first valve group switch 5, the second valve group switch 9, the second bus switch 10, and the third bus switch 6 are in the closed position
  • the first bus switch 12 is in the position.
  • the voltage source converter 2 and the current-limiting reactor 11 A DC circuit breaker with breaking DC fault current is connected in series, or the first busbar switch 12 adopts a DC circuit breaker with breaking DC fault current, or the voltage source converter 2 of the hybrid DC converter of the inverter station 28 and the limiter are used.
  • a diode valve block is connected in series between the current reactor 11 to block the reverse current of the voltage source converter 2.
  • the anode of the diode valve block and the negative electrode of the voltage source converter are the common connection end, or the hybrid DC of the inverter station 28
  • the inverter adopts the circuit structure of Fig. 8E and Fig. 8F. It should be pointed out that the reverse current of the voltage source converter 2 in the hybrid DC converter of the inverter station 28 flows from the negative electrode of the voltage source converter 2 to the positive electrode.
  • Figure 11 is a high-voltage direct current transmission device consisting of a current source valve unit on the rectifier side and two hybrid DC converters on the inverter side, showing the commutation of the high voltage direct current transmission device by a traditional current source valve group
  • the rectifier station 27 of the high-voltage direct current transmission device is composed of a topological structure 30 in which current source valve units are connected in series, and the inverter station 28 is composed of the topological structure 25 in FIG. 8C and the topological structure 26 in FIG. 8D respectively. And the negative inverter.
  • the grid-commutated converter 1 is connected to the secondary winding of a current source high-voltage direct current transmission transformer 18 based on a thyristor.
  • the voltage source converter 2 is connected to the secondary winding of the high voltage direct current transmission transformer 19 based on the voltage source converter.
  • the rectifier station 27 is equipped with an AC filter 32 to filter out harmonics and provide reactive power, and is separated and combined with the AC power grid 22 through an AC switch 31.
  • a bridge arm reactor 20 is provided in order to suppress the bridge arm circulating current of the voltage source converter and the surge current under fault.
  • a smoothing reactor 13 and a current-limiting reactor 11 are provided in order to smooth the DC voltage of the DC circuit and suppress the DC fault current.
  • Fig. 11 shows a ground electrode wire 16 for connecting the converter to the ground electrode.
  • the rectifier station 27 arranges the DC filter 14 between the DC line 15 and the ground electrode conductor 16.
  • a DC filter 14 is arranged between the DC bus 29 of the inverter station 28 and the valve group connection line 17.
  • the second valve group switch 9 is close to the voltage source converter 2 side and the first bus switch 12 is connected across the DC bus.
  • the first bypass switch 4, the second bypass switch 8, the third bypass switch 3, and the fourth bypass switch The switch 7 is in the position, the first valve group switch 5, the second valve group switch 9, the second bus switch 10, and the third bus switch 6 are in the closed position, and the first bus switch 12 is in the position.
  • the current converter 2 blocks or controls the DC current of the voltage source converter 2 to be equal to or less than the minimum current (preferably zero); the first bus switch 12 and the second bus switch 10 of the voltage source valve group unit are separated. At this point, the voltage source converter 2 exits operation.
  • the rectifier station 27 cooperates with the inverter station 28 to exit the power grid commutating converter 1 online.
  • the voltage source converter 2 and the current-limiting reactor 11 A DC circuit breaker with breaking DC fault current is connected in series, or the first busbar switch 12 adopts a DC circuit breaker with breaking DC fault current, or the voltage source converter 2 of the hybrid DC converter of the inverter station 28 and the limiter are used.
  • a diode valve block is connected in series between the galvanic reactor 11 to block the reverse current of the voltage source converter 2.
  • the cathode of the diode valve block and the anode of the voltage source converter are the common connection end, or the hybrid DC of the inverter station 28
  • the inverter adopts the circuit structure of Fig. 8E and Fig. 8F. It should be pointed out that the reverse current of the voltage source converter 2 in the hybrid DC converter of the inverter station 28 flows from the negative electrode of the voltage source converter 2 to the positive electrode.
  • Fig. 12 is an online exit device of a hybrid DC converter provided by an embodiment of the present application, which is used to implement online exit of the hybrid DC converter. It includes a detection unit 34 and a control unit 35.
  • the detection unit 34 is used to detect the first DC voltage, the first DC current, the first unlock signal, the first lock signal, and the first operating signal of the current source valve group unit, and the second DC voltage of the voltage source valve group unit ,
  • the second direct current, the second unlock signal, the second lock signal, the second operation signal detect the first valve group switch 5, the first bus switch 12, the first bypass switch 4, the second valve group switch 9 Or the position of the second bus switch 10 and the second bypass switch 8.
  • the control unit 35 is used to control the voltage source converter to exit when both the grid phase commutated converter and the voltage source converter have an unlock signal and an operating signal, and when an operator's command is received to exit the voltage source converter. Specifically: control the DC voltage of the power grid commutation converter 1 to zero or a smaller value; if the current source valve group unit includes the third bypass switch 3, close the third bypass switch 3, and when the third bypass is detected After the switch 3 is in the closed position, lock the grid commutating converter 1 or control the grid commutating converter 1 to shift the phase.
  • the current source valve group unit does not include the first
  • the three bypass switch 3 closes the first bypass switch 4, and when it is detected that the first bypass switch 4 is in the closed position, the grid phase-changing converter 1 is blocked or the phase-shifting of the grid phase-changing converter 1 is controlled.
  • the current source valve group unit includes a third bypass switch 3, it will send a separate The command of the third bypass switch 3 issues a command to separate the first valve group switch 5 of the current source type valve group unit.
  • a command to close the first bus switch 12 of the current source valve group unit is issued.
  • the grid phase commutated converter 1 and the voltage source converter 2 are connected in parallel.
  • the grid commutating converter 1 If the grid commutating converter 1 is locked, the grid commutating converter 1 will be unlocked. If the grid commutating converter 1 is controlled to shift the phase, the grid commutating converter 1 will be controlled to cancel the phase shift and control the DC power. Transfer from voltage source converter 2 to grid commutated converter 1, control the voltage source converter to block or control the DC current of the voltage source converter to be equal to or less than the minimum current, and issue a command to separate the second valve group switch 9 When it is detected that the second valve group switch 9 is in the position, the voltage source inverter 2 exits.
  • first bus switch 12 is used to connect the voltage source converter 2 and the DC bus or the neutral bus across the current source valve unit unit, a command to close the first bus switch 12 of the current source valve unit is issued, when When it is detected that the first busbar switch 12 of the current source valve group unit is in the closed position, the grid phase commutated converter 1 and the voltage source converter 2 are connected in parallel. Issue a command to separate the first bypass switch 4 of the current source valve group unit.
  • the current source valve group unit includes a third bypass switch 3, issue a command to separate the third bypass switch 3 and issue a separate second valve group switch 9 command, when it is detected that the first bypass switch 4, the third bypass switch 3 and the second valve group switch 9 of the current source valve group unit are in the position, the second bypass switch of the voltage source valve group unit is closed
  • the switch 8 commands that when it is detected that the second bypass switch 8 of the voltage source valve group unit is in the closed position, the voltage source converter 2 is connected in parallel with the grid commutating converter 1. If the grid commutating converter 1 is locked, the grid commutating converter 1 will be unlocked.
  • the grid commutating converter 1 If the grid commutating converter 1 is controlled to shift the phase, the grid commutating converter 1 will be controlled to cancel the phase shift and control the DC power. Transfer from voltage source converter 2 to grid commutated converter 1, control voltage source converter 2 to block or control voltage source converter DC current to be equal to or less than the minimum current, and issue a separate voltage source valve group unit The command of the first bus switch 12, when it is detected that the first bus switch 12 of the voltage source valve group unit is in the position, the voltage source converter 2 is isolated. At this point, the voltage source converter 2 exits.
  • the converter on-line exit circuit and exit method and device proposed in this application are used for the on-line exit of the voltage source converter of the hybrid DC converter, and is particularly suitable for a narrow DC voltage adjustment range or a voltage whose DC voltage cannot be adjusted to zero voltage.
  • Source inverter used for the on-line exit of the voltage source converter of the hybrid DC converter, and is particularly suitable for a narrow DC voltage adjustment range or a voltage whose DC voltage cannot be adjusted to zero voltage.

Abstract

一种混合直流换流器在线退出电路、退出方法及退出装置。所述换流器包括串接的电流源型阀组单元和电压源型阀组单元，电流源型阀组单元包括电网换相换流器（1），电压源型阀组单元包括电压源换流器（2），所述退出电路包括：第一阀组开关（5），连接电网换相换流器（1）与电压源型阀组单元；第一母线开关（12），连接电网换相换流器（1）与直流母线或中性母线，或连接电压源换流器（2）与直流母线或中性母线；第一旁通开关（4），与第一阀组开关（5）和电网换相换流器（1）的串联电路并联连接；第二阀组开关（9），连接电压源换流器（2）与电流源型阀组单元，或/和第二母线开关（10），连接电压源换流器（2）与直流母线或中性母线；第二旁通开关（8），与电压源换流器（2）和第二阀组开关（9）或/和第二母线开关（10）的串联电路并联连接。

Description

混合直流换流器在线退出电路、退出方法及退出装置 技术领域
本申请涉及直流输电技术领域，具体涉及混合直流换流器在线退出电路、退出方法及退出装置。
背景技术
基于晶闸管的电流源型高压直流输电优点为换流器损耗小，发生直流线路故障时可通过移相来重启直流系统。缺点是逆变侧换流器工作在有源逆变，不能接入无源系统。逆变侧接入弱交流系统出现扰动后容易发生换相失败。无功消耗大，电压、电流谐波含量高，需要安装滤波装置提供无功功率和滤波。基于电压源换流器的直流输电优点为可控性高，可接入无源系统，不需要无功补偿装置。缺点为换流器开关损耗大，采用半桥结构的模块化多电平换流器不能控制直流侧故障时的故障电流，在故障发生后只能通过断开交流侧断路器来切除故障。
ABB公司对于直流侧故障，采用增加直流线路的直流断路器来解决直流侧故障，但是直流断路器成本高、可靠性还有待验证。西门子公司对于直流侧故障，采用全桥电路结构的模块化多电平换流器来解决，但是全桥电路结构的换流器损耗大。阿尔斯通公司对于直流侧故障，采用全桥电路并且桥臂串联电力电子开关器件的方式来解决，但是可靠性还有待验证。浙江大学对于直流侧故障，采用在主回路串联二极管来解决，但是二极管不参与功率变换，自身会产生损耗。
南瑞继保公司对于直流侧故障，提出一种带旁通支路的电网换相换流器和电压源换流器串联的混合直流换流器，电压源换流器只需采用半桥电路结构的模块化多电平换流器，电网换相换流器能自然阻断直流侧故障电流，旁通支路又能可靠保护电压源换流器，运行方式也更加灵活。混合直流换流器中的电压源换流器为半桥电路结构的模块化多电平换流器，电压调节范围有限，不同于电网换相换流器，不能调节电压为零实现在线退出。
如果电压源换流器因系统运行方式或检修要求退出时，需要混合直流换流器停运或者通过短暂控制混合直流换流器的直流电流为零分开电压源换流器的连接刀闸或开关才能退出运行。虽然可以实现电压源换流器在线退出，但是退出过程中直流功率会中断，如果在退出过程中出现连接刀闸或开关故障，极有可能会引起直流闭锁，影响直流输电系统功率平稳运行。
发明内容
本申请实施例提供一种混合直流换流器在线退出电路，所述混合直流换流器包括串联连接的电流源型阀组单元和电压源型阀组单元，所述电流源型阀组单元包括电网换相换流器，所述电压源型阀组单元包括电压源换流器，其中，所述在线退出电路包括第一阀组开关、第一母线开关、第一旁通开关、第二阀组开关或/和第二母线开关、第二旁通开关，所述第一阀组开关用于连接所述电网换相换流器与所述电压源型阀组单元；所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线，或者用于跨所述电流源型阀组单元连接所述电压源换流器与直流母线或中性母线；所述第一旁通开关与所述第一阀组开关和所述电网换相换流器的串联电路并联连接；所述第二阀组开关用于连接所述电压源换流器与所述电流源型阀组单元；所述第二母线开关用于连接所述电压源换流器与所述直流母线或所述中性母线；所述第二旁通开关与所述电压源换流器和所述第二阀组开关或/和所述第二母线开关的串联电路并联连接。
根据一些实施例，所述电压源型阀组单元包括并联连接的至少一个所述电压源换流器。
根据一些实施例，所述电流源型阀组单元为低端阀组时，所述第一母线开关用于连接所述电网换相换流器与所述直流母线，所述第二母线开关用于连接所述电压源换流器与所述直流母线；或者所述第一母线开关用于连接所述电压源换流器与所述中性母线，所述第二母线开关用于连接所述电压源换流器与所述直流母线。
根据一些实施例，所述电流源型阀组单元为高端阀组时，所述第一母线开关用于连接所述电网换相换流器与所述中性母线，所述第二母线开关用于连接所述电压源换流器与所述中性母线；或者所述第一母线开关用于连接所述电压源换流器与所述直流母线，所述第二母线开关用于连接所述电压源换流器与 所述中性母线。
根据一些实施例，所述电流源型阀组单元的阴极与所述电压源型阀组单元的负极连接。
根据一些实施例，所述电流源型阀组单元的阳极与所述电压源型阀组单元的正极连接。
根据一些实施例，所述电流源型阀组单元的阴极与所述电压源型阀组单元的正极连接。
根据一些实施例，所述电流源型阀组单元的阳极与所述电压源型阀组单元的负极连接。
根据一些实施例，所述电压源型阀组单元还包括限流电抗器，所述限流电抗器与所述电压源换流器串联连接。
根据一些实施例，所述电压源型阀组单元还包括第四旁通开关，所述第四旁通开关与所述限流电抗器和所述电压源换流器的串联电路并联连接。
根据一些实施例，所述电流源型阀组单元还包括第三母线开关，所述电流源型阀组单元为低端阀组时，所述第三母线开关用于连接所述电网换相换流器与所述中性母线；所述电流源型阀组单元为高端阀组时，用于连接所述电网换相换流器与所述直流母线。
根据一些实施例，所述电流源型阀组单元还包括第三旁通开关，所述第三旁通开关用于连接所述电网换相换流器的阳极和阴极。
根据一些实施例，所述在线退出电路还包括二极管阀组，所述二极管阀组与第一母线开关或/和第一旁通开关或/和第三旁通开关的并联电路串联连接；所述二极管阀组由多个二极管串联组成。
根据一些实施例，所述开关包括机械开关、刀闸、直流断路器、晶闸管阀组的至少一种。
根据一些实施例，所述电网换相换流器包括六脉动桥式电路、十二脉动桥式电路的至少一种，所述脉动桥式电路包括不可关断的半控型功率半导体器件。
根据一些实施例，所述电压源换流器包括两电平换流器、二极管箝位型多电平换流器、模块化多电平换流器MMC、混合多电平换流器HMC、两电平级联型换流器CSL、堆叠式两电平换流器CTL的至少一种，所述换流器包括可关断的全控型功率半导体器件。
本申请实施例还提供一种混合直流换流器在线退出方法，应用在上述所述的混合直流换流器在线退出电路，当所述电网换相换流器和所述电压源换流器同时运行、需要退出电压源换流器时，所述在线退出方法包括：闭合所述第一旁通开关，闭锁所述电网换相换流器或控制所述电网换相换流器移相；通过开关转换，将所述电网换相换流器与所述电压源换流器并联连接；解锁所述电网换相换流器或解除所述电网换相换流器移相，将直流功率从所述电压源换流器转移到所述电网换相换流器；控制所述电压源换流器闭锁或者控制所述电压源换流器直流电流等于或小于电流最小值；隔离所述电压源换流器。
根据一些实施例，如果所述电流源型阀组单元包括第三旁通开关，所述闭合所述第一旁通开关，闭锁所述电网换相换流器或控制所述电网换相换流器移相，包括：闭合所述第三旁通开关，闭锁所述电网换相换流器或控制所述电网换相换流器移相，在所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线时，闭合所述第一旁通开关。
根据一些实施例，在闭合所述第三旁通开关或所述第一旁通开关前，控制所述电网换相换流器直流电压为零或较小值。
根据一些实施例，所述控制所述电网换相换流器直流电压为零或较小值，包括：控制所述电网换相换流器的触发角介于85度至95度之间，以控制所述电网换相换流器直流电压为零或较小值，典型值为90度；或/和控制所述电网换相换流器控制投入旁通对，以控制所述电网换相换流器直流电压为较小值；所述较小值大于零，小于直流电压额定值的0.1倍。
根据一些实施例，所述控制所述电网换相换流器移相，包括：控制所述电网换相换流器的触发角介于120度至180度之间，以控制所述电网换相换流器移相。
根据一些实施例，在所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线时，所述开关转换包括：分开所述第一阀组开关，闭合所述第一母线开关；在所述第一母线开关用于跨所述电流源型阀组单元连接所述电压源换流器与直流母线或中性母线时，所述开关转换包括：闭合所述第一母线开关，分开所述第一旁通开关，分开所述第二阀组开关，闭合所述第二旁通开关。
根据一些实施例，如果所述电流源型阀组单元包括第三旁通开关，在所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线时，所述分开所述第一阀组开关之前还包括：分开所述第三旁通开关；在所述第一母线开关用于跨所述电流源型阀组单元连接所述电压源换 流器与直流母线或中性母线时，所述分开所述第一旁通开关之前还包括：分开所述第三旁通开关。
根据一些实施例，当所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线，所述第一母线开关的两端并联辅助电阻时，所述闭合所述第一母线开关前，还包括：投入所述辅助电阻；当所述辅助电阻流过电流为零或极小值时，再闭合所述第一母线开关；确定所述第一母线开关闭合后，切除所述辅助电阻；当所述第一母线开关用于跨所述电流源型阀组单元连接所述电压源换流器与直流母线或中性母线，所述第二旁通开关的两端并联辅助电阻时，所述闭合所述第二旁通开关前，还包括：投入所述辅助电阻；当所述辅助电阻流过电流为零或极小值时，再闭合所述第二旁通开关；确定所述第二旁通开关闭合后，切除所述辅助电阻。
根据一些实施例，当所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线时，所述隔离电压源换流器包括：分开所述第二阀组开关或/和所述第二母线开关；当所述第一母线开关用于跨所述电流源型阀组单元连接所述电压源换流器与直流母线或中性母线时，所述隔离电压源换流器包括：至少分开所述第一母线开关。
本申请实施例还提供一种混合直流换流器在线退出装置，应用在如上所述的混合直流换流器在线退出电路，当所述电网换相换流器和所述电压源换流器同时运行、需要退出电压源换流器时，所述在线退出装置包括检测单元和控制单元，所述检测单元检测所述电流源型阀组单元的第一直流电压、第一直流电流、第一解锁信号、第一闭锁信号、第一运行信号，检测所述电压源型阀组单元的第二直流电压、第二直流电流、第二解锁信号、第二闭锁信号、第二运行信号，检测所述第一阀组开关、所述第一母线开关、所述第一旁通开关、所述第二阀组开关或所述第二母线开关、所述第二旁通开关的位置；所述控制单元闭合所述第一旁通开关，闭锁所述电网换相换流器或控制所述电网换相换流器移相，通过开关转换，将所述电网换相换流器与所述电压源换流器并联连接，解锁所述电网换相换流器或解除所述电网换相换流器移相，将直流功率从所述电压源换流器转移到所述电网换相换流器，控制所述电压源换流器闭锁或者控制所述电压源换流器直流电流等于或小于电流最小值，隔离所述电压源换流器。
本申请实施例提供的技术方案，通过先闭锁混合直流换流器的电网换相换流器，将电压源换流器与电网换相换流器并联连接，解锁电网换相换流器，将电压源换流器的功率转移到电网换相换流器，控制电压源换流器闭锁，隔离电压源换流器，实现电压源换流器的在线平滑退出，保证直流输电系统功率平稳运行。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1A是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的拓扑结构图之一。
图1B是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的拓扑结构图之二。
图1C是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的拓扑结构图之三。
图1D是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的拓扑结构图之四。
图2是本申请实施例提供的一种混合直流换流器在线退出电路。
图3A是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图之一。
图3B是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图之二。
图3C是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图之三。
图3D是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图之四。
图3E是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图之五。
图3F是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图之六。
图4是本申请实施例提供的一种混合直流换流器在线退出方法流程示意图。
图5是由图3A～图3D四种混合直流换流器拓扑结构组成、低端阀组采用电流源型阀组单元的高压直流输电装置。
图6是由图3A～图3D四种混合直流换流器拓扑结构组成、高端阀组采用电流源型阀组单元的高压直流输电装置。
图7是整流侧采用电流源型阀组单元和逆变侧由图3C和图3D两种混合直流换流器组成的高压直流 输电装置。
图8A是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图之七。
图8B是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图之八。
图8C是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图之九。
图8D是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图之十。
图8E是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图十一。
图8F是本申请混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的具体结构图十二。
图9是由图8A～图8D四种混合直流换流器拓扑结构组成、低端阀组采用电压源型阀组单元的高压直流输电装置。
图10是由图8A～图8D四种混合直流换流器拓扑结构组成、高端阀组采用电压源型阀组单元的高压直流输电装置。
图11是整流侧采用电流源型阀组单元和逆变侧由图8C和图8D两种混合直流换流器组成的高压直流输电装置。
图12是本申请实施例提供的一种混合直流换流器换流器在线退出装置。
具体实施方式
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清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
应当理解，本申请的权利要求、说明书及附图中的术语“第一”、“第二”、“第三”等是用于区别不同对象，而不是用于描述特定顺序。本申请的说明书和权利要求书中使用的术语“包括”指示所描述特征、整体、步骤、操作、元素和/或组件的存在，但并不排除一个或多个其它特征、整体、步骤、操作、元素、组件和/或其集合的存在或添加。
图1A至图1D是本申请实施例提供的一种混合直流换流器中电流源型阀组单元和电压源型阀组单元相连接的四种拓扑结构。
如图1A所示，电流源型阀组单元的阴极X1和电压源型阀组单元的负极X4相连。如图1B所示，电流源型阀组单元的阳极X2和电压源型阀组单元的正极X3相连。如图1C所示，电流源型阀组单元的阴极X1和电压源型阀组单元的正极X3相连。如图1D所示，电流源型阀组单元的阳极X2和电压源型阀组单元的负极X4相连。
图2是本申请实施例提供的一种混合直流换流器在线退出电路。
如图2所示，混合直流换流器包括串联连接的电流源型阀组单元和电压源型阀组单元。电流源型阀组单元包括电网换相换流器1，电压源型阀组单元包括并联连接的至少一个电压源换流器2。
电网换相换流器1包括六脉动桥式电路、十二脉动桥式电路的至少一种，脉动桥式电路包括不可关断的半控型功率半导体器件，如晶闸管。电压源换流器2包括两电平换流器、二极管箝位型多电平换流器、模块化多电平换流器MMC、混合多电平换流器HMC、两电平级联型换流器CSL、堆叠式两电平换流器CTL的至少一种，所述换流器包括可关断的全控型功率半导体器件，如IGBT。
混合直流换流器在线退出电路用于在线退出电压源换流器2。混合直流换流器在线退出电路包括第一阀组开关5、第一母线开关12、第一旁通开关4、第二阀组开关9或/和第二母线开关10、第二旁通开关8。在本实施例中，同时包括第二阀组开关9和第二母线开关10。
第一阀组开关5用于连接电网换相换流器1与电压源型阀组单元。第一母线开关12用于连接电网换相换流器1与直流母线或中性母线。在图2实施例中，第一母线开关12用于跨所述电压源型阀组单元连接电网换相换流器1与直流母线。第一旁通开关4与第一阀组开关5和电网换相换流器1的串联电路并联连接。第二阀组开关9用于连接电压源换流器2与电流源型阀组单元。第二母线开关10用于连接电压源换流器2与直流母线或中性母线。在图2实施例中，第二母线开关10用于连接电压源换流器2与直流母线。第二旁通开关8，与电压源换流器2与第二阀组开关9或/和第二母线开关10的串联电路并联连接。
图2、图3A～图3F、图4、图5和图6所示电路结构中第一母线开关12用于跨所述电压源型阀组单元连接电网换相换流器1与直流母线或中性母线。
在图3A中，电流源型阀组单元的阴极X1与电压源型阀组单元的负极X4连接。在图3B中，电流源 型阀组单元的阳极X2与电压源型阀组单元的正极X3连接。在图3C中，电流源型阀组单元的阴极X1与电压源型阀组单元的正极X3连接。在图3D中，电流源型阀组单元的阳极X2与电压源型阀组单元的负极X4连接。在图3E中，电流源型阀组单元的阴极X1与电压源型阀组单元的正极X3连接。在图3F中，电流源型阀组单元的阳极X2与电压源型阀组单元的负极X4连接。
如图3A至3F所示，电流源型阀组单元为低端阀组时，第一母线开关12用于连接电网换相换流器1与直流母线，第二母线开关10用于连接电压源换流器2与直流母线。电流源型阀组单元为高端阀组时，第一母线开关12用于连接电网换相换流器1与中性母线，第二母线开关10用于连接电压源换流器2与中性母线。电压源换流器2、限流电抗器11、第二阀组开关9或/和第二母线开关10的串联连接后的电路，与第二旁通开关8并联连接。
可选地，如图3A至3F所示，为了抑制直流故障电流，设置限流电抗器11。
可选地，如图3A至3F所示，电压源型阀组单元还包括第四旁通开关7，限流电抗器11和电压源换流器2串联连接后的电路与第四旁通开关7并联连接。
可选地，如图3A至3F所示，电流源型阀组单元还包括第三母线开关6，用于连接电网换相换流器1与中性母线或直流母线。电流源型阀组单元为低端阀组时，第三母线开关6用于连接电网换相换流器1与中性母线。电流源型阀组单元为高端阀组时，第三母线开关6用于连接电网换相换流器1与直流母线。
可选地，如图3A至3F所示，电流源型阀组单元还包括第三旁通开关3，用于连接电网换相换流器1的阳极和阴极。
可选地，如图3E至3F所示，混合直流换流器在线退出电路还包括二极管阀组36，与第一旁通开关4和第三旁通开关3的并联电路串联连接；二极管阀组36由多个二极管串联组成。在上述实施例中提到的各种开关，包括机械开关、刀闸、直流断路器、晶闸管阀组的至少一种。其中，晶闸管阀组由多个晶闸管串联组成。
当电网换相换流器1和电压源换流器2同时运行时，第一阀组开关5、第二阀组开关9或/和第二母线开关10处于合位，第一母线开关12、第一旁通开关4和第二旁通开关8处于分位。需要退出电压源换流器2时，混合直流换流器在线退出方法包括以下流程，如图4所示。
在S110中，闭合第一旁通开关4，闭锁电网换相换流器1或控制电网换相换流器1移相。
具体步骤为：控制电网换相换流器1直流电压为零或较小值。
如果电流源型阀组单元包括第三旁通开关3，闭合第三旁通开关3，闭锁电网换相换流器1或控制电网换相换流器1移相，闭合第一旁通开关4；如果电流源型阀组单元不包括第三旁通开关3，闭合第一旁通开关4，闭锁电网换相换流器1或控制电网换相换流器1移相。
上述控制电网换相换流器1直流电压为零或较小值为控制电网换相换流器1的触发角介于85度至95度之间，以控制电网换相换流器1的直流电压为零或较小值，典型值为90度。或/和控制电网换相换流器1控制投入旁通对，以控制电网换相换流器1的直流电压为较小值。上述较小值大于零，小于直流电压额定值的0.1倍。上述控制电网换相换流器1移相为控制电网换相换流器1的触发角介于120度至180度之间，典型值为164度。
在S120中，通过开关转换，将电网换相换流器1与电压源换流器2并联连接。
开关转换包括：如果电流源型阀组单元包括第三旁通开关3，分开第三旁通开关3，分开第一阀组开关5，闭合第一母线开关12；如果电流源型阀组单元不包括第三旁通开关3，分开第一阀组开关5，闭合第一母线开关12。此时，电网换相换流器1与电压源换流器2并联连接。
闭合第一母线开关12之前，为了防止产生较大的闭合电流，如果在第一母线开关12两端并联辅助电阻，先投入辅助电阻，当辅助电阻流过电流为零或极小值时，再闭合第一母线开关12，第一母线开关12闭合后切除辅助电阻。电流极小值为小于第一母线开关12能承受的闭合电流的电流值。
在S130中，如果在S110中闭锁电网换相换流器1，则解锁电网换相换流器1，如果在S110中控制电网换相换流器1移相，则控制电网换相换流器1解除移相，将直流功率从电压源换流器2转移到电网换相换流器1。
在S140中，控制电压源换流器2闭锁或者控制电压源换流器2直流电流等于或小于电流最小值。电流最小值小于或等于第二阀组开关9或者第二母线开关10的分断电流值，优选地，电流最小值为零。
在S150中，分开第二阀组开关9或/和第二母线开关10，隔离电压源换流器2。
图5是由图3A～图3D四种混合直流换流器拓扑结构组成、低端阀组采用电流源型阀组单元的高压直流输电装置，示出了高压直流输电装置全部由图3A至图3D所示的四种结构组成、电流源型阀组单元为低端阀组的一个实施例。
如图5所示，通过直流线路15将整流站27和逆变站28相连。整流站27由图3A中的结构23和图3B中的结构24分别组成其正极换流器和负极换流器。逆变站28由图3C中的结构25和图3D中的26分别组成其负极换流器和正极换流器。电网换相换流器1与基于晶闸管的电流源型高压直流输电变压器18次级绕组相连，电压源换流器2与基于电压源换流器的高压直流输电变压器19次级绕组相连。
要指出的是，交流电网是三相的，然而在图5中为清楚起见仅示出一相。高压直流输电变压器的初级绕组借助交流开关21与交流电网22分合。如果采用电压源换流器2为电网换相换流器1提供无功功率，则交流滤波器少配置或不配置。为了抑制电压源换流器2的桥臂环流和故障下的浪涌电流，设置桥臂电抗器20。为了平滑直流电路的直流电压和抑制直流故障电流，设置平波电抗器13和限流电抗器11。
图5中示出接地极导线16，用于换流器与接地极的连接。中性母线33和阀组连接线17之间配置直流滤波器14。电流源型阀组单元的第一阀组开关5靠近电网换相换流器1侧和直流母线29之间跨接第一母线开关12。混合直流换流器在线退出电路用于在线退出电压源换流器2。图5中的电流源型阀组单元为低端阀组，换流器在线退出电路至少包括电流源型阀组单元的第一阀组开关5、第一母线开关12、第一旁通开关4、第二阀组开关9或第二母线开关10、第二旁通开关8。
当电网换相换流器1和电压源换流器2同时运行时，电流源型阀组单元的第一阀组开关5和第三母线开关6处于合位，第一母线开关12、第三旁通开关3和第一旁通开关4处于分位。第二阀组开关9和第二母线开关10处于合位。第四旁通开关7处于关断或分开状态，第二旁通开关8处于分位。
当需要退出电压源换流器2时，控制电网换相换流器1电压为零或较小值，然后闭合电流源型阀组单元的第三旁通开关3，闭锁电网换相换流器1，闭合第一旁通开关4；分开电流源型阀组单元的第三旁通开关3，分开电流源型阀组单元的第一阀组开关5，闭合电流源型阀组单元的第一母线开关12，将电网换相换流器1与电压源换流器2并联连接；解锁电网换相换流器1，将直流功率从电压源换流器2转移到电网换相换流器1，控制电压源换流器2闭锁；分开第二阀组开关9或/和第二母线开关10，隔离电压源换流器2。至此，电压源换流器2退出运行。整流站27和逆变站28可分别同时进行上述操作实现电压源换流器2退出运行。
为了防止在电压源换流器2并联到电网换相换流器1期间，因直流线路或者交流线路发生故障引起直流输电系统闭锁，可选地，电压源换流器2与限流电抗器11之间串联具有分断直流故障电流的直流断路器，或者第一母线开关12采用具有分断直流故障电流的直流断路器，或者逆变站28的混合直流换流器的电压源换流器2与限流电抗器11之间串联一个阻断电压源换流器2反向电流的二极管阀组，二极管阀组的阴极与电压源换流器的正极为公共连接端或者二极管阀组的阳极与电压源换流器的负极为公共连接端，或者逆变站28的混合直流换流器采用图3E和图3F的电路结构。需要指出的是，逆变站28的混合直流换流器中的电压源换流器2的反向电流是从电压源换流器2的负极流向正极。
图6是由图3A～图3D四种混合直流换流器拓扑结构组成、高端阀组采用电流源型阀组单元的高压直流输电装置，示出了高压直流输电装置全部由图3A至图3D所示的四种结构组成、电流源型阀组单元为高端阀组的一个实施例。
如图6所示，通过直流线路15将整流站27和逆变站28相连。整流站27由图3A中的结构23和图3B中的结构24分别组成其负极换流器和正极换流器。逆变站28由图3C中的结构25和图3D中的结构26分别组成其正极换流器和负极换流器。电网换相换流器1与基于晶闸管的电流源型高压直流输电变压器18次级绕组相连。电压源换流器2与基于电压源换流器的高压直流输电变压器19次级绕组相连。
要指出的是，交流电网是三相的，然而在图6中为清楚起见仅示出一相。高压直流输电变压器的初级绕组借助交流开关21与交流电网22分合。如果采用电压源换流器2为电网换相换流器1提供无功功率，则交流滤波器少配置或不配置。为了抑制电压源换流器2的桥臂环流和故障下的浪涌电流，设置桥臂电抗器20。为了平滑直流电路的直流电压和抑制直流故障电流，设置平波电抗器13和限流电抗器11。图6中示出接地极导线16用于换流器与接地极的连接。直流母线29和阀组连接线17之间配置直流滤波器14。电流源型阀组单元的第一阀组开关5靠近电网换相换流器1侧和中性母线33之间跨接第一母线开关12。
混合直流换流器在线退出电路用于在线退出电压源换流器2，图6中的电流源型阀组单元为高端阀组。 换流器在线退出电路至少包括电流源型阀组单元的第一阀组开关5、第一母线开关12、第一旁通开关4、第二阀组开关9或者第二母线开关10、第二旁通开关8。
当电网换相换流器1和电压源换流器2同时运行时，电流源型阀组单元的第一阀组开关5和第三母线开关6处于合位，第一母线开关12、第三旁通开关3和第一旁通开关4处于分位。第二阀组开关9和第二母线开关10处于合位，第四旁通开关7处于关断或分开状态，第二旁通开关8处于分位。
当需要退出电压源换流器2时，控制电网换相换流器1电压为零或较小值，闭合电流源型阀组单元的第三旁通开关3，闭锁电网换相换流器1，闭合第一旁通开关4；分开电流源型阀组单元的第三旁通开关3，分开电流源型阀组单元的第一阀组开关5，闭合电流源型阀组单元的第一母线开关12，将电网换相换流器1与电压源换流器2并联连接；解锁电网换相换流器1，将直流功率从电压源换流器2转移到电网换相换流器1，控制电压源换流器2闭锁；分开第二阀组开关9或/和第二母线开关10，隔离电压源换流器2。至此，电压源换流器2退出运行。整流站27和逆变站28可分别同时进行上述操作实现电压源换流器2退出运行。
为了防止在电压源换流器2并联到电网换相换流器1期间，因直流线路或者交流线路发生故障引起直流输电系统闭锁，可选地，电压源换流器2与限流电抗器11之间串联具有分断直流故障电流的直流断路器，或者第一母线开关12采用具有分断直流故障电流的直流断路器，或者逆变站28的混合直流换流器的电压源换流器2与限流电抗器11之间串联一个阻断电压源换流器2反向电流的二极管阀组，二极管阀组的阴极与电压源换流器的正极为公共连接端或者二极管阀组的阳极与电压源换流器的负极为公共连接端，或者逆变站28的混合直流换流器采用图3E和图3F的电路结构。需要指出的是，逆变站28的混合直流换流器中的电压源换流器2的反向电流是从电压源换流器2的负极流向正极。
图7是整流侧采用电流源型阀组单元和逆变侧由图3C和图3D两种混合直流换流器组成的高压直流输电装置，示出了高压直流输电装置由传统的电流源型阀组组成的换流器和图3C、图3D所示两种结构组成的一个实施例。
高压直流输电装置整流站27由电流源型阀组单元串联的结构30组成，逆变站28由图3C中的结构25和图3D中的结构26分别组成其正极换流器和负极换流器。电网换相换流器1与基于晶闸管的电流源型高压直流输电变压器18次级绕组相连，电压源换流器2与基于电压源换流器的高压直流输电变压器19次级绕组相连。
整流站27配置交流滤波器32滤除谐波和提供无功功率，通过交流开关31与交流电网22分合。为了抑制电压源换流器的桥臂环流和故障下的浪涌电流，设置桥臂电抗器20。为了平滑直流电路的直流电压和抑制直流故障电流，设置平波电抗器13和限流电抗器11。图7中示出接地极导线16用于换流器与接地极的连接。整流站27在直流线路15和接地极导线16之间配置直流滤波器14。逆变站28在直流母线29和阀组连接线17之间配置直流滤波器14。电流源型阀组单元的第一阀组开关5靠近电网换相换流器1侧和中性母线33之间跨接第一母线开关12。
混合直流换流器在线退出电路用于在线退出电压源换流器2，图7中的电流源型阀组单元为高端阀组，换流器在线退出电路至少包括电流源型阀组单元的第一阀组开关5、第一母线开关12、第一旁通开关4、第二阀组开关9或者第二母线开关10、第二旁通开关8。
当电网换相换流器1和电压源换流器2同时运行时，电流源型阀组单元的第一阀组开关5和第三母线开关6处于合位，第一母线开关12、第三旁通开关3和第一旁通开关4处于分位。第二阀组开关9和第二母线开关10处于合位，第四旁通开关7处于关断或分开状态，第二旁通开关8处于分位。
当需要退出电压源换流器2时，控制电网换相换流器1电压为零或较小值，闭合电流源型阀组单元的第三旁通开关3，闭锁电网换相换流器1，闭合第一旁通开关4；分开电流源型阀组单元的第三旁通开关3，分开第一阀组开关5，闭合第一母线开关12，将电网换相换流器1与电压源换流器2并联连接；解锁电网换相换流器1，将直流功率从电压源换流器2转移到电网换相换流器1，控制电压源换流器2闭锁；分开第二阀组开关9或/和第二母线开关10，隔离电压源换流器2。至此，电压源换流器2退出运行。整流站27配合逆变站28在线退出电网换相换流器1。
为了防止在电压源换流器2并联到电网换相换流器1期间，因直流线路或者交流线路发生故障引起直流输电系统闭锁，可选地，电压源换流器2与限流电抗器11之间串联具有分断直流故障电流的直流断路器，或者第一母线开关12采用具有分断直流故障电流的直流断路器，或者逆变站28的混合直流换流器的电压源换流器2与限流电抗器11之间串联一个阻断电压源换流器2反向电流的二极管阀组，二极管 阀组的阴极与电压源换流器的正极为公共连接端或者二极管阀组的阳极与电压源换流器的负极为公共连接端，或者逆变站28的混合直流换流器采用图3E和图3F的电路结构。需要指出的是，逆变站28的混合直流换流器中的电压源换流器2的反向电流是从电压源换流器2的负极流向正极。
图8A～图8F、图9、图10和图11所示电路结构中第一母线开关12用于跨所述电流源型阀组单元连接电压源换流器2与直流母线或中性母线。
如图8A至图8F所示,混合直流换流器包括串联连接的电流源型阀组单元和电压源型阀组单元。电流源型阀组单元包括电网换相换流器1，电压源型阀组单元包括并联连接的至少一个电压源换流器2。
电网换相换流器1包括六脉动桥式电路、十二脉动桥式电路的至少一种，脉动桥式电路包括不可关断的半控型功率半导体器件，如晶闸管。电压源换流器2包括两电平换流器、二极管箝位型多电平换流器、模块化多电平换流器MMC、混合多电平换流器HMC、两电平级联型换流器CSL、堆叠式两电平换流器CTL的至少一种，所述换流器包括可关断的全控型功率半导体器件，如IGBT。
如图8A至8F所示，第一阀组开关5用于连接电网换相换流器1与电压源型阀组单元。第三母线开关6用于连接电网换相换流器1与直流母线或中性母线。电网换相换流器1与第一阀组开关5或/和第三母线开关6的串联电路与第一旁通开关4并联连接。第二阀组开关9用于连接电压源换流器2与电流源型阀组单元。第二母线开关10用于连接电压源换流器2与中性母线或直流母线。第一母线开关12用于连接电压源换流器2与直流母线或中性母线。电压源换流器2与第二阀组开关9或/和第二母线开关10的串联电路与第二旁通开关8并联连接。第三旁通开关3用于连接电网换相换流器1的阳极与阴极。其中，电压源型阀组单元为低端阀组时，第一母线开关12用于连接电压源换流器2与直流母线，第二母线开关10用于连接电压源换流器2与中性母线。电压源型阀组单元为高端阀组时，第一母线开关12用于连接电压源换流器2与中性母线，第二母线开关10用于连接电压源换流器2与直流母线。
为了抑制直流故障电流，设置限流电抗器11。第四旁通开关7用于连接电压源换流器2的正极与负极。为了抑制直流故障电流，可在电压源换流器2的正极或负极串联二极管阀组或者直流断路器。
在图8E和图8F中，混合直流换流器在线退出电路还包括二极管阀组36，与第一母线开关和第一旁通开关和第三旁通开关的并联电路串联连接；二极管阀组36由多个二极管串联组成。
在图8A中，电流源型阀组单元的阴极X1与电压源型阀组单元的负极X4连接。在图8B中，电流源型阀组单元的阳极X2与电压源型阀组单元的正极X3连接。在图8C中，电流源型阀组单元的阴极X1与电压源型阀组单元的正极X3连接。在图8D中，电流源型阀组单元的阳极X2与电压源型阀组单元的负极X4连接。在图8E中，电流源型阀组单元的阴极X1与电压源型阀组单元的正极X3连接。在图8F中，电流源型阀组单元的阳极X2与电压源型阀组单元的负极X4连接。
在上述实施例中提到的各种开关，包括机械开关、刀闸、直流断路器、晶闸管阀组的至少一种。
当电网换相换流器1和电压源换流器2同时运行时，第一阀组开关5、第二阀组开关9处于合位，第一母线开关12、第一旁通开关4、第二旁通开关8、第三旁通开关3处于分位。如果电流源型阀组单元包括第三母线开关6，则第三母线开关6处于合位。如果电压源型阀组单元包括第二母线开关10，则第二母线开关10处于合位。如果电压源型阀组单元包括第四旁通开关7，则第四旁通开关7处于分位。需要退出电压源换流器2时，混合直流换流器阀组在线退出方法流程包括以下流程，如图4所示。
在S110中，闭合第一旁通开关4，闭锁电网换相换流器1或控制电网换相换流器1移相。
具体步骤为：控制电网换相换流器1直流电压为零或较小值。
如果电流源型阀组单元包括第三旁通开关3，闭合第三旁通开关3，闭锁电网换相换流器1或控制电网换相换流器1移相，可选地，进一步闭合第一旁通开关4；如果电流源型阀组单元不包括第三旁通开关3，闭合第一旁通开关4，闭锁电网换相换流器1或控制电网换相换流器1移相。
在S120中，通过开关转换，将电压源换流器2与电网换相换流器1并联连接。
开关转换包括：闭合电压源型阀组单元的第一母线开关12，分开电流源型阀组单元的第一旁通开关4，分开第二阀组开关9，闭合电压源型阀组单元的第二旁通开关8。此时，电压源换流器2与电网换相换流器1并联连接。
如果在S110中闭合的是第三旁通开关3，则开关转换包括：闭合电压源型阀组单元的第一母线开关12，分开电流源型阀组单元的第三旁通开关3，分开第二阀组开关9，闭合电压源型阀组单元的第二旁通开关8。此时，电压源换流器2与电网换相换流器1并联连接。
如果在S110中同时闭合了第一旁通开关4和第三旁通开关3，则开关转换包括：闭合电压源型阀组 单元的第一母线开关12，分开电流源型阀组单元的第一旁通开关4和第三旁通开关3，分开第二阀组开关9，闭合电压源型阀组单元的第二旁通开关8。此时，电压源换流器2与电网换相换流器1并联连接。
分开电流源型阀组单元的第一旁通开关4或/和第三旁通开关3，和分开第二阀组开关9没有先后顺序要求。闭合第二旁通开关8之前，为了防止产生较大的闭合电流，可选地，在第二旁通开关8的两端并联辅助电阻，先投入辅助电阻，当辅助电阻流过电流为零或极小值时，再闭合第二旁通开关8，确定第二旁通开关8闭合后切除辅助电阻。电流极小值为小于第二旁通开关8能承受的闭合电流的电流值。
在S130中，如果在S110中闭锁电网换相换流器1，则解锁电网换相换流器1，如果在S110中控制电网换相换流器1移相，则控制电网换相换流器1解除移相，将直流功率从电压源换流器2转移到电网换相换流器1。
在S140中，控制电压源换流器2闭锁或者控制电压源换流器2的直流电流等于或小于电流最小值。
电流最小值小于或等于第一母线开关12或者第二母线开关10的分断电流值。
在S150中，分开第一母线开关12，隔离电压源换流器2。
如果电压源型阀组单元包括第二母线开关10，分开第一母线开关12时，同时分开第二母线开关10。第二母线开关10用于连接电压源换流器2与直流母线或中性母线。
图9是由图8A～图8D四种混合直流换流器拓扑结构组成、低端阀组采用电压源型阀组单元的高压直流输电装置的一个实施例。
通过直流线路15将整流站27和逆变站28相连。整流站27由图8A中的拓扑结构23和图8B中的拓扑结构24分别组成其负极换流器和正极换流器。逆变站28由图8C中的拓扑结构25和图8D中的拓扑结构26分别组成其正极换流器和负极换流器。电网换相换流器1与基于晶闸管的电流源型高压直流输电变压器18次级绕组相连。电压源换流器2与基于电压源换流器的高压直流输电变压器19次级绕组相连。
要指出的是，交流电网是三相的，然而在图4中为清楚起见仅示出一相。高压直流输电变压器的初级绕组借助交流开关21与交流电网22分合。如果采用电压源换流器2为电网换相换流器1提供无功功率，则交流滤波器少配置或不配置。为了抑制电压源换流器的桥臂环流和故障下的浪涌电流，设置桥臂电抗器20。为了平滑直流电压和抑制直流故障电流，设置平波电抗器13和限流电抗器11。图9中示出接地极导线16，用于换流器与接地极的连接。直流母线29和阀组连接线17之间配置直流滤波器14。第二阀组开关9靠近电压源换流器2侧和直流母线之间跨接第一母线开关12。
当混合直流换流器的电网换相换流器1和电压源换流器2同时运行时，第一旁通开关4、第二旁通开关8、第三旁通开关3和第四旁通开关7处于分位，第一阀组开关5、第二阀组开关9、第二母线开关10、第三母线开关6处于合位，第一母线开关12处于分位。
需要退出电压源换流器2时，控制电网换相换流器1直流电压为零或较小值，闭合第三旁通开关3，闭锁电网换相换流器1或控制电网换相换流器1移相；进行开关转换，闭合电压源型阀组单元的第一母线开关12，分开电流源型阀组单元的第三旁通开关3，分开第二阀组开关9，闭合电压源型阀组单元的第二旁通开关8，使电压源换流器2与电网换相换流器1并联连接；如果上述闭锁电网换相换流器1，则解锁电网换相换流器1，如果上述控制电网换相换流器1移相，则控制电网换相换流器1解除移相，将直流功率从电压源换流器2转移到电网换相换流器1；控制电压源换流器2闭锁或者控制电压源换流器2直流电流等于或小于电流最小值(优选为零)；分开电压源型阀组单元的第一母线开关12和第二母线开关10。至此，电压源换流器2退出运行。整流站27和逆变站28可分别同时进行上述操作实现电压源换流器2退出运行。
为了防止在电压源换流器2并联到电网换相换流器1期间，因直流线路或者交流线路发生故障引起直流输电系统闭锁，可选地，电压源换流器2与限流电抗器11之间串联具有分断直流故障电流的直流断路器，或者第一母线开关12采用具有分断直流故障电流的直流断路器，或者逆变站28的混合直流换流器的电压源换流器2与限流电抗器11之间串联一个阻断电压源换流器2反向电流的二极管阀组，二极管阀组的阴极与电压源换流器2的正极为公共连接端，或者逆变站28的混合直流换流器采用图8E和图8F的电路结构。需要指出的是，逆变站28的混合直流换流器中的电压源换流器2的反向电流是从电压源换流器2的负极流向正极。
图10是由四种混合直流换流器拓扑结构组成、高端阀组采用电压源型阀组单元的高压直流输电装置，示出了高压直流输电装置全部由图8A至图8D所示的四种结构组成、电压源型阀组单元为高端阀组的一个实施例。
通过直流线路15将整流站27和逆变站28相连。整流站27由图8A中的拓扑结构23和图8B中的拓扑结构24分别组成其正极换流器和负极换流器。逆变站28由图8C中的拓扑结构25和图8D中的拓扑结构26分别组成其负极换流器和正极换流器。电网换相换流器1与基于晶闸管的电流源型高压直流输电变压器18次级绕组相连。电压源换流器2与基于电压源换流器的高压直流输电变压器19次级绕组相连。
高压直流输电变压器的初级绕组借助交流开关21与交流电网22分合，如果采用电压源换流器2为电网换相换流器1提供无功功率，则交流滤波器少配置或不配置。为了抑制电压源换流器的桥臂环流和故障下的浪涌电流，设置桥臂电抗器20。为了平滑直流电压和抑制直流故障电流，设置平波电抗器13和限流电抗器11。图10中示出接地极导线16，其用于换流器与接地极的连接。中性母线33和阀组连接线17之间配置直流滤波器14。第二阀组开关9靠近电压源换流器2侧和中性母线33之间跨接第一母线开关12。当混合直流换流器的电网换相换流器1和电压源换流器2同时运行时，第一旁通开关4、第二旁通开关8、第三旁通开关3和第四旁通开关7处于分位，第一阀组开关5、第二阀组开关9、第二母线开关10、第三母线开关6处于合位，第一母线开关12处于分位。
需要退出电压源换流器2时，控制电网换相换流器1直流电压为零或较小值，闭合第三旁通开关3，闭锁电网换相换流器1或控制电网换相换流器1移相；进行开关转换，闭合电压源型阀组单元的第一母线开关12，分开电流源型阀组单元的第三旁通开关3，分开第二阀组开关9，闭合电压源型阀组单元的第二旁通开关8，将电压源换流器2与电网换相换流器1并联连接；如果上述闭锁电网换相换流器1，则解锁电网换相换流器1，如果上述控制电网换相换流器1移相，则控制电网换相换流器1解除移相，将直流功率从电压源换流器2转移到电网换相换流器1；控制电压源换流器2闭锁或者控制电压源换流器2直流电流等于或小于电流最小值(优选为零)；分开电压源型阀组单元的第一母线开关12和第二母线开关10。至此，电压源换流器2退出运行。整流站27和逆变站28可分别同时进行上述操作实现电压源换流器2退出运行。
为了防止在电压源换流器2并联到电网换相换流器1期间，因直流线路或者交流线路发生故障引起直流输电系统闭锁，可选地，电压源换流器2与限流电抗器11之间串联具有分断直流故障电流的直流断路器，或者第一母线开关12采用具有分断直流故障电流的直流断路器，或者逆变站28的混合直流换流器的电压源换流器2与限流电抗器11之间串联一个阻断电压源换流器2反向电流的二极管阀组，二极管阀组的阳极与电压源换流器的负极为公共连接端，或者逆变站28的混合直流换流器采用图8E和图8F的电路结构。需要指出的是，逆变站28的混合直流换流器中的电压源换流器2的反向电流是从电压源换流器2的负极流向正极。
图11是整流侧采用电流源型阀组单元和逆变侧由两种混合直流换流器组成的高压直流输电装置，示出了高压直流输电装置由传统的电流源型阀组组成的换流器和图8C、图8D所示的两种结构组成的一个实施例。
高压直流输电装置整流站27由电流源型阀组单元串联的拓扑结构30组成，逆变站28由拓扑结构图8C中的拓扑结构25和图8D中的拓扑结构26分别组成其正极换流器和负极换流器。电网换相换流器1与基于晶闸管的电流源型高压直流输电变压器18次级绕组相连。电压源换流器2与基于电压源换流器的高压直流输电变压器19次级绕组相连。
整流站27配置交流滤波器32滤除谐波和提供无功功率，通过交流开关31与交流电网22分合。为了抑制电压源换流器的桥臂环流和故障下的浪涌电流，设置桥臂电抗器20。为了平滑直流电路的直流电压和抑制直流故障电流，设置平波电抗器13和限流电抗器11。图11中示出接地极导线16，用于换流器与接地极的连接。整流站27在直流线路15和接地极导线16之间配置直流滤波器14。逆变站28直流母线29和阀组连接线17之间配置直流滤波器14。第二阀组开关9靠近电压源换流器2侧和直流母线之间跨接第一母线开关12。当混合直流换流器的电网换相换流器1和电压源换流器2同时运行时，第一旁通开关4、第二旁通开关8、第三旁通开关3和第四旁通开关7处于分位，第一阀组开关5、第二阀组开关9、第二母线开关10、第三母线开关6处于合位，第一母线开关12处于分位。
需要退出电压源换流器2时，控制电网换相换流器1直流电压为零或较小值，闭合第三旁通开关3，闭锁电网换相换流器1或控制电网换相换流器1移相；进行开关转换，闭合电压源型阀组单元的第一母线开关12，分开电流源型阀组单元的第三旁通开关3，分开第二阀组开关9，闭合电压源型阀组单元的第二旁通开关8，将电压源换流器2与电网换相换流器1并联连接；如果上述闭锁电网换相换流器1，则解锁电网换相换流器1，如果上述控制电网换相换流器1移相，则控制电网换相换流器1解除移相，将直流 功率从电压源换流器2转移到电网换相换流器1，控制电压源换流器2闭锁或者控制电压源换流器2直流电流等于或小于电流最小值(优选为零)；分开电压源型阀组单元的第一母线开关12和第二母线开关10。至此，电压源换流器2退出运行。整流站27配合逆变站28在线退出电网换相换流器1。
为了防止在电压源换流器2并联到电网换相换流器1期间，因直流线路或者交流线路发生故障引起直流输电系统闭锁，可选地，电压源换流器2与限流电抗器11之间串联具有分断直流故障电流的直流断路器，或者第一母线开关12采用具有分断直流故障电流的直流断路器，或者逆变站28的混合直流换流器的电压源换流器2与限流电抗器11之间串联一个阻断电压源换流器2反向电流的二极管阀组，二极管阀组的阴极与电压源换流器的正极为公共连接端，或者逆变站28的混合直流换流器采用图8E和图8F的电路结构。需要指出的是，逆变站28的混合直流换流器中的电压源换流器2的反向电流是从电压源换流器2的负极流向正极。
图12是本申请实施例提供的一种混合直流换流器换流器在线退出装置，用于实现混合直流换流器换流器在线退出。包括检测单元34、控制单元35。
检测单元34用于检测电流源型阀组单元的第一直流电压、第一直流电流、第一解锁信号、第一闭锁信号、第一运行信号，检测电压源型阀组单元的第二直流电压、第二直流电流、第二解锁信号、第二闭锁信号、第二运行信号，检测第一阀组开关5、所述第一母线开关12、第一旁通开关4、第二阀组开关9或第二母线开关10、第二旁通开关8的位置。
控制单元35用于当电网换相换流器和电压源换流器都有解锁信号、运行信号，接收到运行人员命令退出电压源换流器时，控制电压源换流器退出。具体为：控制电网换相换流器1直流电压为零或较小值；如果电流源型阀组单元包括第三旁通开关3，闭合第三旁通开关3，当检测到第三旁通开关3处于合位后，闭锁电网换相换流器1或控制电网换相换流器1移相，可选地，进一步闭合第一旁通开关4；如果电流源型阀组单元不包括第三旁通开关3，闭合第一旁通开关4，当检测到第一旁通开关4处于合位后，闭锁电网换相换流器1或控制电网换相换流器1移相。
如果第一母线开关12用于跨所述电压源型阀组单元连接电网换相换流器1与直流母线或中性母线，如果电流源型阀组单元包括第三旁通开关3，发出分开第三旁通开关3的命令，发出分开电流源型阀组单元的第一阀组开关5的命令。当检测到电流源型阀组单元的第一阀组开关5处于分位时，发出闭合电流源型阀组单元的第一母线开关12的命令。当检测到电流源型阀组单元的第一母线开关12位于合位时，电网换相换流器1与电压源换流器2实现并联连接。如果上述闭锁电网换相换流器1，则解锁电网换相换流器1，如果上述控制电网换相换流器1移相，则控制电网换相换流器1解除移相，控制直流功率从电压源换流器2转移到电网换相换流器1，控制电压源换流器闭锁或者控制电压源换流器直流电流等于或小于电流最小值，发出分开第二阀组开关9的命令，当检测到第二阀组开关9处于分位时，电压源换流器2退出。
如果第一母线开关12用于跨所述电流源型阀组单元连接电压源换流器2与直流母线或中性母线，发出闭合电流源型阀组单元的第一母线开关12的命令，当检测到电流源型阀组单元的第一母线开关12位于合位时，电网换相换流器1与电压源换流器2并联连接。发出分开电流源型阀组单元的第一旁通开关4命令，如果电流源型阀组单元包括第三旁通开关3，发出分开第三旁通开关3的命令，发出分开第二阀组开关9命令，当检测到电流源型阀组单元的第一旁通开关4、第三旁通开关3和第二阀组开关9处于分位时，闭合电压源型阀组单元的第二旁通开关8命令，当检测到电压源型阀组单元的第二旁通开关8处于合位时，电压源换流器2与电网换相换流器1并联连接。如果上述闭锁电网换相换流器1，则解锁电网换相换流器1，如果上述控制电网换相换流器1移相，则控制电网换相换流器1解除移相，控制直流功率从电压源换流器2转移到电网换相换流器1，控制电压源换流器2闭锁或者控制电压源换流器直流电流等于或小于电流最小值，发出分开电压源型阀组单元的第一母线开关12的命令，当检测到电压源型阀组单元的第一母线开关12处于分位时，电压源换流器2隔离。至此，电压源换流器2退出。
本申请所提出的换流器在线退出电路和退出方法及装置用于混合直流换流器的电压源换流器在线退出，特别适用于直流电压调节范围窄或不能调节直流电压到零压的电压源换流器。
以上对本申请实施例进行了详细介绍，文中应用了具体个例对本申请的原理及实施方式进行了阐述，以上实施例的说明仅用于帮助理解本申请的方法及其核心思想。本领域技术人员依据本申请的思想，基于本申请的具体实施方式及应用范围上做出的改变或变形之处，都属于本申请保护的范围。综上所述，本说明书内容不应理解为对本申请的限制。

Claims (26)

  1. 一种混合直流换流器在线退出电路，所述混合直流换流器包括串联连接的电流源型阀组单元和电压源型阀组单元，所述电流源型阀组单元包括电网换相换流器，所述电压源型阀组单元包括电压源换流器，其中，所述在线退出电路包括：
    第一阀组开关，用于连接所述电网换相换流器与所述电压源型阀组单元；
    第一母线开关，用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线，或者用于跨所述电流源型阀组单元连接所述电压源换流器与直流母线或中性母线；
    第一旁通开关，与所述第一阀组开关和所述电网换相换流器的串联电路并联连接；
    第二阀组开关或/和第二母线开关，所述第二阀组开关用于连接所述电压源换流器与所述电流源型阀组单元；所述第二母线开关用于连接所述电压源换流器与所述直流母线或所述中性母线；
    第二旁通开关，与所述电压源换流器和所述第二阀组开关或/和所述第二母线开关的串联电路并联连接。
  2. 根据权利要求1所述的在线退出电路，其中，所述电压源型阀组单元包括并联连接的至少一个所述电压源换流器。
  3. 根据权利要求1所述的在线退出电路，其中，所述电流源型阀组单元为低端阀组时，所述第一母线开关用于连接所述电网换相换流器与所述直流母线，所述第二母线开关用于连接所述电压源换流器与所述直流母线；或者所述第一母线开关用于连接所述电压源换流器与所述中性母线，所述第二母线开关用于连接所述电压源换流器与所述直流母线。
  4. 根据权利要求1所述的在线退出电路，其中，所述电流源型阀组单元为高端阀组时，所述第一母线开关用于连接所述电网换相换流器与所述中性母线，所述第二母线开关用于连接所述电压源换流器与所述中性母线；或者所述第一母线开关用于连接所述电压源换流器与所述直流母线，所述第二母线开关用于连接所述电压源换流器与所述中性母线。
  5. 根据权利要求1所述的在线退出电路，其中，所述电流源型阀组单元的阴极与所述电压源型阀组单元的负极连接。
  6. 根据权利要求1所述的在线退出电路，其中，所述电流源型阀组单元的阳极与所述电压源型阀组单元的正极连接。
  7. 根据权利要求1所述的在线退出电路，其中，所述电流源型阀组单元的阴极与所述电压源型阀组单元的正极连接。
  8. 根据权利要求1所述的在线退出电路，其中，所述电流源型阀组单元的阳极与所述电压源型阀组单元的负极连接。
  9. 根据权利要求1所述的在线退出电路，其中，所述电压源型阀组单元还包括：
    限流电抗器，与所述电压源换流器串联连接。
  10. 根据权利要求1所述的在线退出电路，其中，所述电压源型阀组单元还包括：
    第四旁通开关，与所述限流电抗器和所述电压源换流器的串联电路并联连接。
  11. 根据权利要求1所述的在线退出电路，其中，所述电流源型阀组单元还包括：
    第三母线开关，所述电流源型阀组单元为低端阀组时，用于连接所述电网换相换流器与所述中性母线；所述电流源型阀组单元为高端阀组时，用于连接所述电网换相换流器与所述直流母线。
  12. 根据权利要求1所述的在线退出电路，其中，所述电流源型阀组单元还包括：
    第三旁通开关，用于连接所述电网换相换流器的阳极和阴极。
  13. 根据权利要求1所述的在线退出电路，还包括：
    二极管阀组，与第一母线开关或/和第一旁通开关或/和第三旁通开关的并联电路串联连接；
    所述二极管阀组由多个二极管串联组成。
  14. 根据权利要求1至13之任一项所述的在线退出电路，其中，所述开关包括机械开关、刀闸、直流断路器、晶闸管阀组的至少一种。
  15. 根据权利要求1所述的在线退出电路，其中，所述电网换相换流器包括六脉动桥式电路、十二脉动桥式电路的至少一种，所述脉动桥式电路包括不可关断的半控型功率半导体器件。
  16. 根据权利要求1所述的在线退出电路，其中，所述电压源换流器包括两电平换流器、二极管箝位型多电平换流器、模块化多电平换流器MMC、混合多电平换流器HMC、两电平级联型换流器CSL、堆叠式两电平换流器CTL的至少一种，所述换流器包括可关断的全控型功率半导体器件。
  17. 一种混合直流换流器在线退出方法，应用在所述权利要求1至16之任一项所述的混合直流换流器在线退出电路，当所述电网换相换流器和所述电压源换流器同时运行、需要退出电压源换流器时，所述在线退出方法包括：
    闭合所述第一旁通开关，闭锁所述电网换相换流器或控制所述电网换相换流器移相；
    通过开关转换，将所述电网换相换流器与所述电压源换流器并联连接；
    解锁所述电网换相换流器或解除所述电网换相换流器移相，将直流功率从所述电压源换流器转移到所述电网换相换流器；
    控制所述电压源换流器闭锁或者控制所述电压源换流器直流电流等于或小于电流最小值；
    隔离所述电压源换流器。
  18. 根据权利要求17所述的在线退出方法，其中，如果所述电流源型阀组单元包括第三旁通开关，所述闭合所述第一旁通开关，闭锁所述电网换相换流器或控制所述电网换相换流器移相，包括：
    闭合所述第三旁通开关，闭锁所述电网换相换流器或控制所述电网换相换流器移相，在所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线时，闭合所述第一旁通开关。
  19. 根据权利要求17或18所述的在线退出方法，其中，在闭合所述第三旁通开关或所述第一旁通开关前，控制所述电网换相换流器直流电压为零或较小值。
  20. 根据权利要求19所述的在线退出方法，其中，所述控制所述电网换相换流器直流电压为零或较小值，包括：
    控制所述电网换相换流器的触发角介于85度至95度之间，以控制所述电网换相换流器直流电压为零或较小值，典型值为90度；
    或/和控制所述电网换相换流器控制投入旁通对，以控制所述电网换相换流器直流电压为较小值；
    所述较小值大于零，小于直流电压额定值的0.1倍。
  21. 根据权利要求17所述的在线退出方法，其中，所述控制所述电网换相换流器移相，包括：
    控制所述电网换相换流器的触发角介于120度至180度之间，以控制所述电网换相换流器移相。
  22. 根据权利要求17所述的在线退出方法，其中，
    在所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线时，所述开关转换包括：
    分开所述第一阀组开关，闭合所述第一母线开关；
    在所述第一母线开关用于跨所述电流源型阀组单元连接所述电压源换流器与直流母线或中性母线时，所述开关转换包括：
    闭合所述第一母线开关，分开所述第一旁通开关，分开所述第二阀组开关，闭合所述第二旁通开关。
  23. 根据权利要求22所述的在线退出方法，如果所述电流源型阀组单元包括第三旁通开关，其中，
    在所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线时，所述分开所述第一阀组开关之前还包括：分开所述第三旁通开关；在所述第一母线开关用于跨所述电流源型阀组单元连接所述电压源换流器与直流母线或中性母线时，所述分开所述第一旁通开关之前还包括：分开所述第三旁通开关。
  24. 根据权利要求17所述的在线退出方法，其中，当所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线，所述第一母线开关的两端并联辅助电阻时，所述闭合所述第一母线开关前，还包括：
    投入所述辅助电阻；
    当所述辅助电阻流过电流为零或极小值时，再闭合所述第一母线开关；
    确定所述第一母线开关闭合后，切除所述辅助电阻；
    当所述第一母线开关用于跨所述电流源型阀组单元连接所述电压源换流器与直流母线或中性母线，所述第二旁通开关的两端并联辅助电阻时，所述闭合所述第二旁通开关前，还包括：
    投入所述辅助电阻；
    当所述辅助电阻流过电流为零或极小值时，再闭合所述第二旁通开关；
    确定所述第二旁通开关闭合后，切除所述辅助电阻。
  25. 根据权利要求17所述的在线退出方法，其中，
    当所述第一母线开关用于跨所述电压源型阀组单元连接所述电网换相换流器与直流母线或中性母线时，所述隔离电压源换流器包括：分开所述第二阀组开关或/和所述第二母线开关；
    当所述第一母线开关用于跨所述电流源型阀组单元连接所述电压源换流器与直流母线或中性母线时，所述隔离电压源换流器包括：至少分开所述第一母线开关。
  26. 一种混合直流换流器在线退出装置，应用在所述权利要求1至16之任一项所述的混合直流换流器在线退出电路，当所述电网换相换流器和所述电压源换流器同时运行、需要退出电压源换流器时，所述在线退出装置包括：
    检测单元，检测所述电流源型阀组单元的第一直流电压、第一直流电流、第一解锁信号、第一闭锁信号、第一运行信号，检测所述电压源型阀组单元的第二直流电压、第二直流电流、第二解锁信号、第二闭锁信号、第二运行信号，检测所述第一阀组开关、所述第一母线开关、所述第一旁通开关、所述第二阀组开关或所述第二母线开关、所述第二旁通开关的位置；
    控制单元，闭合所述第一旁通开关，闭锁所述电网换相换流器或控制所述电网换相换流器移相，通过开关转换，将所述电网换相换流器与所述电压源换流器并联连接，解锁所述电网换相换流器或解除所述电网换相换流器移相，将直流功率从所述电压源换流器转移到所述电网换相换流器，控制所述电压源换流器闭锁或者控制所述电压源换流器直流电流等于或小于电流最小值，隔离所述电压源换流器。
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