CN112787347B - Online exit circuit, exit method and exit device for hybrid direct-current converter valve bank - Google Patents
Online exit circuit, exit method and exit device for hybrid direct-current converter valve bank Download PDFInfo
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- CN112787347B CN112787347B CN201911095357.1A CN201911095357A CN112787347B CN 112787347 B CN112787347 B CN 112787347B CN 201911095357 A CN201911095357 A CN 201911095357A CN 112787347 B CN112787347 B CN 112787347B
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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
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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
- H02J2003/365—Reducing harmonics or oscillations in HVDC
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- 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]
Abstract
The application provides an online exit circuit, an exit method and an exit device for a hybrid direct current converter valve bank. The hybrid direct current converter comprises a current source type valve bank unit and a voltage source type valve bank unit which are connected in series, the current source type valve bank unit comprises a power grid commutation converter, the voltage source type valve bank unit comprises a voltage source converter, the hybrid direct current converter valve bank online exit circuit comprises a first valve bank switch, a first bus switch, a first bypass switch, a second valve bank switch or a second bus switch, and the first valve bank switch is used for connecting the power grid commutation converter and the voltage source type valve bank unit; the first bus switch is used for connecting the power grid commutation converter and a direct-current bus or a neutral bus; the first bypass switch is connected in parallel with the series circuit of the first valve bank switch and the grid commutation converter; the second valve group switch is used for connecting the voltage source converter and the current source type valve group unit; the second bus switch is used for connecting the voltage source converter and the neutral bus or the direct current bus.
Description
Technical Field
The application relates to the technical field of direct current transmission, in particular to an online exit circuit, an exit method and an exit device for a hybrid direct current converter valve bank.
Background
The thyristor-based current source type high-voltage direct-current transmission has the advantages that the loss of a converter is small, and a direct-current system can be restarted by phase shifting when a direct-current line fault occurs. The inverter side converter works in active inversion and cannot be connected to a passive system. The inversion side is accessed into a weak alternating current system, and phase commutation failure is easy to occur after disturbance occurs. The reactive power consumption is large, the harmonic content of voltage and current is high, and a filtering device is required to be installed to provide reactive power and filtering. The direct current transmission based on the voltage source converter has the advantages of high controllability, capability of being connected into a passive system and no need of a reactive power compensation device. The defects are that the switching loss of the converter is large, the modularized multi-level converter adopting a half-bridge structure cannot control the fault current when the direct current side fails, and the fault can be removed only by disconnecting the circuit breaker on the alternating current side after the fault occurs.
For the direct current side fault, the ABB company adopts a direct current breaker added with a direct current line to solve the direct current side fault, but the direct current breaker has high cost and the reliability needs to be verified. For direct-current side faults, siemens corporation adopts a modular multilevel converter with a full-bridge circuit structure to solve the direct-current side faults, but the converter with the full-bridge circuit structure has large loss. For the direct current side fault, the alstonia company adopts a full bridge circuit and a bridge arm to be connected with a power electronic switching device in series to solve the problem, but the reliability is still to be verified. For direct current side faults, the problem is solved by serially connecting diodes in a main loop, but the diodes do not participate in power conversion and generate loss.
For direct current side faults, south rui relay protection company provides a hybrid direct current converter with a bypass branch circuit and a power grid commutation converter connected in series with a voltage source converter, the voltage source converter only needs a modular multilevel converter with a half-bridge circuit structure, the power grid commutation converter can naturally block direct current side fault current, the bypass branch circuit can reliably protect the voltage source converter, and the operation mode is more flexible. A voltage source converter in the hybrid direct current converter is a modular multilevel converter with a half-bridge circuit structure, the voltage regulation range is limited, and the voltage regulation range is different from that of a power grid phase-change converter, and the voltage cannot be regulated to zero to realize online exit.
If the voltage source converter exits due to the system operation mode or the maintenance requirement, the hybrid direct current converter needs to be stopped or the connection knife switch or the switch of the voltage source converter can be separated by temporarily controlling the direct current of the hybrid direct current converter to be zero. Although online exit of the voltage source converter can be realized, direct current power is interrupted in the exit process, and if a connecting knife switch or a switch fails in the exit process, direct current blocking is possibly caused, so that stable operation of the power of a direct current transmission system is influenced.
Disclosure of Invention
The embodiment of the application provides an online exit circuit of a hybrid direct-current converter valve bank, the hybrid direct-current converter comprises a current source type valve bank unit and a voltage source type valve bank unit which are connected in series, the current source type valve bank unit comprises a power grid commutation converter, the voltage source type valve bank unit comprises a voltage source converter, the circuit comprises a first valve bank switch, a first bus switch, a first bypass switch, a second valve bank switch or a second bus switch, and the first valve bank switch is used for connecting the power grid commutation converter and the voltage source type valve bank unit; the first bus switch is used for connecting the power grid commutation converter with a direct current bus or a neutral bus; the first bypass switch is connected in parallel with the first bank switch and the series circuit of the grid commutated converter; the second valve group switch is used for connecting the voltage source converter and the current source valve group unit; the second bus switch is used for connecting the voltage source converter and the direct current bus or the neutral bus.
According to some embodiments, the voltage source valve pack unit comprises at least one of the voltage source converters connected in parallel.
According to some embodiments, when the current source valve group unit is a low-end valve group, the first bus switch is configured to connect the grid commutation converter and the dc bus, and the second bus switch is configured to connect the voltage source converter and the dc bus.
According to some embodiments, when the current source valve group unit is a high-end valve group, the first bus switch is used for connecting the grid commutation converter and the neutral bus, and the second bus switch is used for connecting the voltage source converter and the neutral bus.
According to some embodiments, the cathode of the current source valve block unit is connected with the cathode of the voltage source valve block unit.
According to some embodiments, the anode of the current source valve block unit is connected to the anode of the voltage source valve block unit.
According to some embodiments, the cathode of the current source type valve block unit is connected with the anode of the voltage source type valve block unit.
According to some embodiments, the anode of the current source valve block unit is connected to the cathode of the voltage source valve block unit.
According to some embodiments, the voltage source valve pack unit further comprises a second bypass switch, the series circuit of the voltage source converter and the second valve pack switch or/and the second bus switch being connected in parallel with the second bypass switch.
According to some embodiments, the voltage source valve block unit further comprises a current limiting reactor connected in series with the voltage source converter.
According to some embodiments, the voltage source valve block unit further comprises a fourth bypass switch connected in parallel with the series circuit of the current limiting reactor and the voltage source converter.
According to some embodiments, the current source valve group unit further comprises a third bus switch for connecting the grid commutated converter with a neutral or dc bus.
According to some embodiments, the current source valve group unit further comprises a third bypass switch connecting the anode and the cathode of the grid commutated converter.
According to some embodiments, the switch comprises at least one of a mechanical switch, a knife switch, a dc circuit breaker, a thyristor valve block.
According to some embodiments, the grid commutated converter comprises at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit, and the pulse bridge circuit comprises a non-turn-off semi-controlled power semiconductor device.
According to some embodiments, the voltage source converter comprises at least one of a two-level converter, a diode clamped multi-level converter, a modular multi-level converter MMC, a hybrid multi-level converter HMC, a two-level cascaded converter CSL, a stacked two-level converter CTL, said converter comprising a turn-off fully controlled power semiconductor device.
The embodiment of the present application further provides an online exit method for a hybrid dc converter valve bank, which is applied to the above online exit circuit for a hybrid dc converter valve bank, and when the power grid commutation converter and the voltage source converter operate simultaneously and need to exit the voltage source converter, the method includes: locking the grid commutation converter and closing the first bypass switch; or the direct-current voltage of the power grid commutation converter is controlled to be zero, the first bypass switch is closed, and then the phase shift of the power grid commutation converter is controlled; connecting the grid commutation converter and the voltage source converter in parallel through switch conversion; unlocking the grid commutation converter or removing the grid commutation converter from shifting the phase; transferring direct current power from the voltage source converter to the grid commutated converter; controlling the voltage source converter to be locked or controlling the direct current of the voltage source converter to be equal to or less than the minimum current value; isolating the voltage source converter.
According to some embodiments, the controlling the grid commutated converter dc voltage to be zero comprises: and controlling the trigger angle of the power grid phase-change converter to be between 85 and 95 degrees so as to control the direct-current voltage of the power grid phase-change converter to be 0.
According to some embodiments, said controlling said grid commutated converter phase shift comprises: and controlling the firing angle of the grid commutation converter to be between 120 and 180 degrees so as to control the phase shift of the grid commutation converter.
According to some embodiments, the switching comprises: and opening the first valve group switch and closing the first bus switch.
According to some embodiments, if the current source valve group unit comprises a third bypass switch, wherein said closing the first bypass switch further comprises: closing the third bypass switch; before closing the first bus bar switch, the method further comprises: separating the third bypass switch.
According to some embodiments, if an auxiliary resistor is connected in parallel to the two ends of the first bus switch, before closing the first bus switch, the method further includes: putting the auxiliary resistor; when the current flowing through the auxiliary resistor is zero or a minimum value, closing the first bus switch; and cutting off the auxiliary resistor after the first bus switch is determined to be closed.
According to some embodiments, the isolated voltage source converter comprises: disconnecting the second bank switch or the second bus switch.
The embodiment of the present application further provides an online exit device for a valve bank of a hybrid dc converter, which is applied to the online exit circuit for a valve bank of a hybrid dc converter, when the power grid commutation converter and the voltage source converter operate simultaneously and need to exit the voltage source converter, the device includes a detection unit and a control unit, the detection unit is configured to detect a first dc voltage, a first dc current, a first unlocking signal, a first locking signal, and a first operating signal of the current source valve bank unit, detect a second dc voltage, a second dc current, a second unlocking signal, a second locking signal, and a second operating signal of the voltage source valve bank unit, and detect positions of the first valve bank switch, the first bus switch, the first bypass switch, the second valve bank switch, or the second bus switch; the control unit is used for controlling the power grid commutation converter to be locked and controlling the first bypass switch to be closed; or the direct-current voltage of the power grid commutation converter is controlled to be zero, the first bypass switch is closed, and then the phase shift of the power grid commutation converter is controlled; connecting the grid commutation converter and the voltage source converter in parallel through switch conversion; unlocking a power grid commutation converter or removing the phase shift of the power grid commutation converter; transferring direct current power from the voltage source converter to the grid commutated converter; controlling the voltage source converter to be locked or controlling the direct current of the voltage source converter to be equal to or less than the minimum current value; opening the second valve group switch or the second bus bar switch to isolate the voltage source converter.
According to some embodiments, if the current source valve group unit comprises a third bypass switch, wherein the control unit controls closing of the third bypass switch before closing of the first bypass switch; the control unit controls to open the third bypass switch before closing the first bus switch.
According to the technical scheme, the power grid commutation converter of the hybrid direct current converter is locked firstly, the voltage source converter and the power grid commutation converter are connected in parallel, the power grid commutation converter is unlocked, the power of the voltage source converter is transferred to the power grid commutation converter, the voltage source converter is controlled to be locked, the voltage source converter is isolated, online smooth exit of the voltage source converter is achieved, and stable power operation of a direct current transmission system is guaranteed.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1A is one of topology structural diagrams of a hybrid dc converter according to an embodiment of the present disclosure, where a current source valve group unit and a voltage source valve group unit are connected;
fig. 1B is a second topology structure diagram of a hybrid dc converter according to an embodiment of the present invention, where a current source valve group unit and a voltage source valve group unit are connected;
fig. 1C is a third topology structure diagram of a hybrid dc converter according to an embodiment of the present disclosure, where a current source type valve set unit and a voltage source type valve set unit are connected;
fig. 1D is a fourth topological structure diagram of a hybrid dc converter according to the present invention, in which a current source type valve set unit and a voltage source type valve set unit are connected;
fig. 2 is an online exit circuit of a hybrid dc converter valve set according to an embodiment of the present disclosure;
fig. 3A is one of specific structural diagrams illustrating a connection between a current source valve group unit and a voltage source valve group unit in a hybrid dc converter according to an embodiment of the present disclosure;
fig. 3B is a second specific structural diagram of a connection between a current source type valve set unit and a voltage source type valve set unit in a hybrid dc converter according to an embodiment of the present invention;
fig. 3C is a third specific structural diagram of a connection between a current source valve assembly unit and a voltage source valve assembly unit in a hybrid dc converter according to an embodiment of the present invention;
fig. 3D is a fourth specific structural diagram illustrating a connection between a current source type valve set unit and a voltage source type valve set unit in a hybrid dc converter according to an embodiment of the present invention;
fig. 4 is a schematic flowchart of an online exiting method for a hybrid dc converter valve pack according to an embodiment of the present disclosure;
fig. 5 is a high voltage dc transmission apparatus consisting of four hybrid dc converter topologies, the low side valve block employing current source type valve block units;
FIG. 6 is a high voltage DC transmission apparatus composed of four hybrid DC converter topologies, in which a high-end valve group employs a current source type valve group unit;
fig. 7 is a high-voltage direct-current transmission device with a current source type valve group unit on a rectification side and two mixed direct-current converters on an inversion side;
fig. 8 is an online exit device for a hybrid dc converter according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
It should be understood that the terms "first," "second," "third," and the like in the claims, the description, and the drawings of the present application are used for distinguishing between different objects and not for describing a particular order. The term "comprises/comprising" when used in the specification and claims of this application is taken to specify the presence of stated features, integers, steps, operations, elements, and/or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Fig. 1A to fig. 1D are four topologies for connecting a current source type valve set unit and a voltage source type valve set unit in a hybrid dc converter according to an embodiment of the present application.
As shown in fig. 1A, the cathode X1 of the current source valve assembly unit is connected to the cathode X4 of the voltage source valve assembly unit.
As shown in fig. 1B, the anode X2 of the current source type valve block unit and the anode X3 of the voltage source type valve block unit are connected.
As shown in fig. 1C, the cathode X1 of the current source type valve block unit and the anode X3 of the voltage source type valve block unit are connected.
As shown in fig. 1D, the anode X2 of the current source type valve block unit is connected to the cathode X4 of the voltage source type valve block unit.
Fig. 2 is an online exit circuit of a hybrid dc converter valve set according to an embodiment of the present disclosure.
As shown in fig. 2, the hybrid dc converter includes a current source type valve block unit and a voltage source type valve block unit connected in series. The current source type valve group unit comprises a power grid phase-change converter 1, and the voltage source type valve group unit comprises at least one voltage source converter 2 connected in parallel.
The power grid commutation converter 1 comprises at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit, wherein the pulse bridge circuit comprises a non-turn-off semi-control type power semiconductor device.
The voltage source converter 2 comprises at least one of a two-level converter, a diode clamping type multi-level converter, a modular multi-level converter MMC, a hybrid multi-level converter HMC, a two-level cascade converter CSL and a stacking type two-level converter CTL, wherein the converter comprises a turn-off fully-controlled power semiconductor device.
And the on-line exit circuit of the hybrid direct current converter valve bank is used for exiting the voltage source converter 2 on line. The on-line exit circuit of the hybrid direct current converter valve bank comprises a first valve bank switch 5, a first bus switch 12, a first bypass switch 4, a second valve bank switch 9 or a second bus switch 10. In this embodiment, both the second bank switch 9 and the second bus bar switch 10 are included.
The first valve bank switch 5 is used for connecting the power grid commutation converter 1 and the voltage source type valve bank unit. The first bus switch 12 is used to connect the grid commutated converter 1 to a dc bus or a neutral bus. In the embodiment of fig. 2, a first bus switch 12 is used to connect the grid commutated converter 1 to the dc bus. The first bypass switch 4 is connected in parallel with the series circuit of the first group valve switch 5 and the grid commutation converter 1. The second valve group switch 9 is used for connecting 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 a dc bus or neutral bus. In the embodiment of fig. 2, a second bus switch 10 is used to connect the voltage source converter 2 with the dc bus.
When the current source valve group unit is a low-end valve group, the first bus switch 12 is used to connect the power grid commutation converter 1 and the dc bus, and the second bus switch 10 is used to connect the voltage source converter 2 and the dc bus. When the current source type valve group unit is a high-end valve group, the first bus switch 12 is used for connecting the power grid phase-change converter 1 and the neutral bus, and the second bus switch 10 is used for connecting the voltage source converter 2 and the neutral bus.
In fig. 3A, a cathode X1 of the current source valve assembly unit is connected to a cathode X4 of the voltage source valve assembly unit. In fig. 3B, the anode X2 of the current source valve block unit is connected to the anode X3 of the voltage source valve block unit. In fig. 3C, the cathode X1 of the current source valve block unit is connected to the anode X3 of the voltage source valve block unit. In fig. 3D, the anode X2 of the current source valve assembly unit is connected to the cathode X4 of the voltage source valve assembly unit.
Alternatively, as shown in fig. 3A to 3D, in order to suppress the direct-current fault current, a current limiting reactor 11 is provided.
Optionally, as shown in fig. 3A to 3D, the voltage source valve group unit further includes a second bypass switch 8, and a 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 bar switch 10 is connected in parallel with the second bypass switch 8. The series connection of the current limiting reactor 11 and the voltage source converter is connected in parallel with the second bypass switch 8.
Alternatively, as shown in fig. 3A to 3D, the voltage source valve block unit further includes a fourth bypass switch 7, and a circuit in which the current limiting reactor 11 and the voltage source converter 2 are connected in series is connected in parallel to the fourth bypass switch 7.
Optionally, as shown in fig. 3A to 3D, the current source valve group unit further includes a third bus switch 6 for connecting the grid commutated converter 1 with the neutral bus or the dc bus. When the current source type valve group unit is a low-end valve group, the third bus switch 6 is used for connecting the power grid phase-change converter 1 and the neutral bus. When the current source type valve group unit is a high-end valve group, the third bus switch 6 is used for connecting the power grid phase-change converter 1 and the direct-current bus.
Optionally, as shown in fig. 3A to 3D, the current source valve group unit further includes a third bypass switch 3 connecting the anode and the cathode of the grid commutated converter 1.
The various switches mentioned in the above embodiments include at least one of a mechanical switch, a knife switch, a dc circuit breaker, and a thyristor valve set.
When the grid commutation converter 1 and the voltage source converter 2 operate simultaneously, the first valve group switch 5, the second valve group switch 9 or/and the second bus switch 10 are in the closed position, and the first bus switch 12 and the first bypass switch 4 are in the open position. When the voltage source converter 2 needs to be exited, the online exiting method of the hybrid dc converter valve bank includes the following processes, as shown in fig. 4.
In S110, the dc voltage of the grid commutated converter 1 is blocked or controlled to be zero.
And controlling the firing angle of the power grid phase-change converter 1 to be between 85 and 95 degrees so as to control the direct-current voltage of the power grid phase-change converter 1 to be 0.
In S120, the first bypass switch 4 is closed.
If the control power grid commutation converter 1 is controlled to have zero direct-current voltage in S110, the phase shift of the power grid commutation converter 1 is controlled after the first bypass switch 4 is closed.
And controlling the firing angle of the grid commutation converter 1 to be between 120 and 180 degrees so as to control the phase shift of the grid commutation converter 1.
If the current source type valve block unit includes the third bypass switch 3, the third bypass switch 3 is closed before the first bypass switch 4 is closed.
In S130, the grid commutated converter 1 is connected in parallel with the voltage source converter 2 by switching.
The switching comprises: the first group valve switch 5 is opened and the first bus bar switch 12 is closed. At this time, the grid commutation converter 1 is connected in parallel with the voltage source converter 2.
Before the first bus bar switch 12 is closed, in order to prevent a large closing current from being generated, if an auxiliary resistor is connected in parallel to both ends of the first bus bar switch 12, the auxiliary resistor is firstly put in, when the current flowing through the auxiliary resistor is zero or a minimum value, the first bus bar switch 12 is closed, and the auxiliary resistor is cut off after the first bus bar switch 12 is closed. The current minimum is a current value that is less than the closing current that the first bus switch 12 can withstand.
If the current source valve group unit comprises a third bypass switch 3, the third bypass switch 3 is also opened before closing the first bus bar switch 12.
In S140, the grid commutated converter 1 is unlocked or the phase of the grid commutated converter 1 is removed.
If the blocking of the grid commutated converter 1 is used in S110, the grid commutated converter 1 is unlocked. And if the direct-current voltage of the control power grid commutation converter 1 is zero in S110, the control power grid commutation converter 1 is controlled to remove the phase shift.
The dc power is then transferred from the voltage source converter 2 to the grid commutated converter 1.
In S150, the voltage source converter 2 is controlled to latch or the direct current of the voltage source converter 2 is controlled to be equal to or less than the current minimum value.
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.
In S160, the second bank switch 9 or/and the second bus switch 10 is opened, isolating the voltage source converter 2.
Fig. 5 is a high-voltage dc transmission apparatus composed of four hybrid dc converter topologies, in which a low-side valve block employs a current source type valve block unit, and illustrates an embodiment of the high-voltage dc transmission apparatus composed of all four structures shown in fig. 3A to 3D, in which the current source type valve block unit is a low-side valve block.
As shown in fig. 5, the rectifier station 27 and the inverter station 28 are connected by a dc line 15. The rectifying station 27 is composed of the structure 23 in fig. 3A and the structure 24 in fig. 3B, respectively, for its positive and negative converters. The inversion station 28 consists of the structure 25 in fig. 3C and 26 in fig. 3D for its negative and positive converters, respectively. The power grid commutation converter 1 is connected with a secondary winding of a thyristor-based current source type high-voltage direct-current transmission transformer 18, and the voltage source converter 2 is connected with a secondary winding of a voltage source converter-based high-voltage direct-current transmission transformer 19.
It is noted that the ac grid is three-phase, however, only one phase is shown in fig. 5 for clarity. The primary winding of the high-voltage direct-current transmission transformer is connected with and disconnected from an alternating-current power grid 22 by an alternating-current switch 21. If the voltage source converter 2 is used to provide reactive power for the grid commutation converter 1, the ac filter is configured less or not. In order to suppress the arm ring current and the surge current under failure of the voltage source converter 2, the arm reactors 20 are provided. In order to smooth the direct-current voltage of the direct-current circuit and suppress the direct-current fault current, a smoothing reactor 13 and a current limiting reactor 11 are provided.
In fig. 5 an earth conductor 16 is shown for connection of the inverter to earth. The dc filter 14 is disposed between the neutral bus 33 and the valve group connection line 17. The first valve group switch 5 of the current source type valve group unit is connected across the first bus switch 12 between the side close to the grid commutation converter 1 and the direct current bus 29.
And the on-line exit circuit of the hybrid direct current converter valve bank is used for exiting the voltage source converter 2 on line. The current source type valve group unit in fig. 5 is a low-end valve group, and the converter online exit circuit at least includes a first valve group switch 5, a first bus switch 12, a first bypass switch 4 of the current source type valve group unit, and a second valve group switch 9 or a second bus switch 10 of the voltage source type valve group unit.
When the power grid commutation converter 1 and the voltage source converter 2 operate simultaneously, the first valve bank switch 5 and the third bus switch 6 of the current source type valve bank unit are in the closed position, and the first bus switch 12, the third bypass switch 3 and the first bypass switch 4 are in the open position. The second valve group switch 9 and the second bus bar switch 10 of the voltage source type valve group unit are in the closed position. The fourth bypass switch 7 is in an off or disengaged state and the second bypass switch 8 is in a disengaged state.
When the voltage source converter 2 needs to be quitted, the first quitting method is as follows: firstly, locking a power grid commutation converter 1; then, a third bypass switch 3 and a first bypass switch 4 of the current source type valve group unit are closed; disconnecting a first valve bank switch 5 of the current source type valve bank unit, separating a third bypass switch 3 of the current source type valve bank unit, closing a first bus switch 12 of the current source type valve bank unit, and connecting the power grid phase-change converter 1 and the voltage source converter 2 in parallel; unlocking the power grid commutation converter 1, transferring direct current power from the voltage source converter 2 to the power grid commutation converter 1, and controlling the voltage source converter 2 to be locked; and opening the second valve group switch 9 or/and the second bus switch 10 of the voltage source type valve group unit to isolate the voltage source converter 2. At this point the voltage source converter 2 is taken out of operation. The rectifying station 27 and the inverting station 28 may perform the above operations simultaneously to take out the operation of the voltage source converter 2.
The second exit method is: controlling the trigger angle of the power grid commutation converter to be 90 degrees so as to control the direct-current voltage of the power grid commutation converter 1 to be zero; then, a third bypass switch 3 and a first bypass switch 4 of the current source type valve group unit are closed, and after the third bypass switch and the first bypass switch are closed, the trigger angle of the power grid phase-change converter 1 is controlled to be 164 degrees to realize the phase shifting of the power grid phase-change converter 1; disconnecting a first valve bank switch 5 of the current source type valve bank unit, separating a third bypass switch 3 of the current source type valve bank unit, closing a first bus switch 12 of the current source type valve bank unit, and connecting the power grid commutation converter 1 and the voltage source converter 2 in parallel; controlling the power grid commutation converter 1 to remove phase shift, transferring direct current power from the voltage source converter 2 to the power grid commutation converter 1, and controlling the voltage source converter 2 to be locked; and opening the second valve group switch 9 or/and the second bus switch 10 of the voltage source type valve group unit to isolate the voltage source converter 2. At this point the voltage source converter 2 is taken out of operation. The rectifying station 27 and the inverting station 28 may perform the above operations simultaneously to realize the operation quit of the voltage source converter 2.
In order to prevent the direct current transmission system from being locked due to the fact that a direct current line or an alternating current line fails when the voltage source converter 2 is connected in parallel to the grid phase-change converter 1, optionally, a direct current circuit breaker with a disconnected direct current fault current is added between the voltage source converter 2 and the current limiting reactor 11, or a direct current circuit breaker with a disconnected direct current fault current is adopted as the first bus switch 12, or a diode valve bank for blocking the reverse current of the voltage source converter 2 is connected in series between the first bus switch 12 of the hybrid direct current converter on the inversion side and the voltage source converter 2, and the cathode of the diode valve bank and the anode of the voltage source converter are a common connecting end or the anode of the diode valve bank and the cathode of the voltage source converter are a common connecting end. Note that the reverse current of the voltage source converter 2 in the hybrid dc converter on the inverter side flows from the negative pole to the positive pole of the voltage source converter 2.
Fig. 6 is a high-voltage dc transmission device composed of four hybrid dc converter topologies, in which a high-side valve block employs a current source type valve block unit, and illustrates an embodiment in which the high-voltage dc transmission device is composed of all four structures shown in fig. 3A to 3D, and the current source type valve block unit is a high-side valve block.
As shown in fig. 6, the rectifier station 27 and the inverter station 28 are connected by a dc line 15. The rectifying station 27 is composed of the structure 23 in fig. 3A and the structure 24 in fig. 3B as its negative and positive converters, respectively. The inversion station 28 is composed of the structure 25 in fig. 3C and the structure 26 in fig. 3D as its positive and negative converters, respectively. The power grid commutation converter 1 is connected with a secondary winding of a thyristor-based current source type high-voltage direct-current transmission transformer 18. The voltage source converter 2 is connected to the secondary winding of a voltage source converter based high voltage direct current transmission transformer 19.
It is noted that the ac grid is three-phase, however only one phase is shown in fig. 6 for clarity. The primary winding of the high-voltage direct-current transmission transformer is connected with and disconnected from an alternating-current power grid 22 by an alternating-current switch 21. If the voltage source converter 2 is adopted to provide reactive power for the power grid commutation converter 1, the alternating current filter is configured less or not. In order to suppress the arm ring current and the surge current under failure of the voltage source converter 2, the arm reactors 20 are provided. In order to smooth the dc voltage of the dc circuit and suppress the dc fault current, a smoothing reactor 13 and a current limiting reactor 11 are provided. The earth conductor 16 is shown in fig. 6 for connection of the inverter to the earth. The dc filter 14 is disposed between the dc bus 29 and the block connection line 17. The first valve group switch 5 of the current source type valve group unit is connected across the first bus bar switch 12 between the side close to the power grid commutation converter 1 and the neutral bus bar 33.
The on-line exit circuit of the hybrid dc converter valve set is used to exit the voltage source converter 2 on-line, and the current source valve set unit in fig. 6 is a high-side valve set. The converter online exit circuit at least comprises a first valve bank switch 5, a first bus switch 12, a first bypass switch 4 of a current source type valve bank unit, and a second valve bank switch 9 or a second bus switch 10 of a voltage source type valve bank unit.
When the power grid commutation converter 1 and the voltage source converter 2 operate simultaneously, the first valve bank switch 5 and the third bus switch 6 of the current source type valve bank unit are in an on position, and the first bus switch 12, the third bypass switch 3 and the first bypass switch 4 are in an off position. The second valve group switch 9 and the second bus switch 10 of the voltage source type valve group unit are in closed position, the fourth bypass switch 7 is in off or separated state, and the second bypass switch 8 is in separated position.
When the voltage source converter 2 needs to be quitted, the first quitting method is as follows: firstly, locking a power grid commutation converter 1; a third bypass switch 3 and a first bypass switch 4 of the current source type valve group unit are closed; disconnecting a first valve bank switch 5 of the current source type valve bank unit, separating a third bypass switch 3 of the current source type valve bank unit, closing a first bus switch 12 of the current source type valve bank unit, and connecting the power grid phase-change converter 1 and the voltage source converter 2 in parallel; unlocking the power grid commutation converter 1, transferring direct current power from the voltage source converter 2 to the power grid commutation converter 1, and controlling the voltage source converter 2 to be locked; and opening the second valve group switch 9 or/and the second bus switch 10 of the voltage source type valve group unit to isolate the voltage source converter 2. The voltage source converter 2 is now taken out of operation. The rectifying station 27 and the inverting station 28 may perform the above operations simultaneously to realize the operation quit of the voltage source converter 2.
The second exiting method is as follows: controlling the trigger angle of the power grid commutation converter to be 90 degrees so as to control the direct-current voltage of the power grid commutation converter 1 to be zero; then, a third bypass switch 3 and a first bypass switch 4 of the current source type valve group unit are closed, and after the third bypass switch and the first bypass switch are closed, the trigger angle of the power grid phase-change converter 1 is controlled to be 164 degrees to realize the phase shifting of the power grid phase-change converter 1; disconnecting a first valve bank switch 5 of the current source type valve bank unit, separating a third bypass switch 3 of the current source type valve bank unit, closing a first bus switch 12 of the current source type valve bank unit, and connecting the power grid commutation converter 1 and the voltage source converter 2 in parallel; controlling the power grid commutation converter 1 to remove the phase shift, transferring the direct current power from the voltage source converter 2 to the power grid commutation converter 1, and controlling the voltage source converter 2 to be locked; and opening the second valve group switch 9 or/and the second bus switch 10 of the voltage source type valve group unit to isolate the voltage source converter 2. The voltage source converter 2 is now taken out of operation. The rectifying station 27 and the inverting station 28 may perform the above operations simultaneously to realize the operation quit of the voltage source converter 2.
In order to prevent the direct current transmission system from being locked due to the fact that a direct current line or an alternating current line fails when the voltage source converter 2 is connected in parallel to the grid commutation converter 1, optionally, a direct current circuit breaker with a disconnected direct current fault current is added between the voltage source converter 2 and the current limiting reactor 11, or a direct current circuit breaker with a disconnected direct current fault current is adopted as the first bus switch 12, or a diode valve bank for blocking the reverse current of the voltage source converter 2 is connected in series between the first bus switch 12 of the hybrid direct current converter on the inversion side and the voltage source converter 2, and the cathode of the diode valve bank and the anode of the voltage source converter are a common connecting end or the anode of the diode valve bank and the cathode of the voltage source converter are a common connecting end. Note that the reverse current of the voltage source converter 2 in the hybrid dc converter on the inverter side flows from the negative pole to the positive pole of the voltage source converter 2.
Fig. 7 is a high-voltage direct-current transmission device with a current source type valve bank unit on a rectification side and two hybrid direct-current converters on an inversion side, and shows an embodiment of the high-voltage direct-current transmission device with a converter consisting of a conventional current source type valve bank and two structures shown in fig. 3C and 3D.
The rectifying station 27 of the high-voltage direct-current transmission device consists of a structure 30 formed by connecting current source type valve group units in series, and the inverting station 28 consists of a structure 25 in fig. 3C and a structure 26 in fig. 3D respectively to form a positive pole converter and a negative pole converter of the high-voltage direct-current transmission device. The power grid commutation converter 1 is connected with a secondary winding of a thyristor-based current source type high-voltage direct-current transmission transformer 18, and the voltage source converter 2 is connected with a secondary winding of a voltage source converter-based high-voltage direct-current transmission transformer 19.
The rectifier station 27 is provided with an ac filter 32 for filtering out harmonics and supplying reactive power, which is connected to and disconnected from the ac power grid 22 via an ac switch 31. In order to suppress the bridge-arm circulating current of the voltage source converter and the surge current under failure, a bridge-arm reactor 20 is provided. In order to smooth the dc voltage of the dc circuit and suppress the dc fault current, a smoothing reactor 13 and a current limiting reactor 11 are provided. The earth conductor 16 is shown in fig. 7 for connection of the inverter to earth. The rectifier station 27 is provided with a dc filter 14 between the dc line 15 and the earth conductor 16. The inverter station 28 is provided with a dc filter 14 between the dc bus 29 and the valve block connection line 17. The first valve group switch 5 of the current source type valve group unit is connected across the first bus bar switch 12 between the side close to the grid commutation converter 1 and the neutral bus bar 33.
The hybrid dc converter valve group online exit circuit is used for exiting the voltage source converter 2 online, the current source type valve group unit in fig. 7 is a high-end valve group, and the converter online exit circuit at least includes a first valve group switch 5, a first bus switch 12, a first bypass switch 4 of the current source type valve group unit, and a second valve group switch 9 or a second bus switch 10 of the voltage source type valve group unit.
When the power grid commutation converter 1 and the voltage source converter 2 operate simultaneously, the first valve bank switch 5 and the third bus switch 6 of the current source type valve bank unit are in an on position, and the first bus switch 12, the third bypass switch 3 and the first bypass switch 4 are in an off position. The second valve group switch 9 and the second bus switch 10 of the voltage source type valve group unit are in closed position, the fourth bypass switch 7 is in off or separated state, and the second bypass switch 8 is in separated position.
When the voltage source converter 2 needs to be exited, the first exiting method is as follows: firstly, locking a power grid commutation converter 1; a third bypass switch 3 and a first bypass switch 4 of the current source type valve group unit are closed; disconnecting the first valve group switch 5, disconnecting the third bypass switch 3 of the current source type valve group unit, closing the first bus switch 12, and connecting the power grid phase-change converter 1 and the voltage source converter 2 in parallel; unlocking the power grid phase-change converter 1, transferring direct-current power from the voltage source converter 2 to the power grid phase-change converter 1, and controlling the voltage source converter 2 to be locked; and opening the second valve group switch 9 or/and the second bus switch 10 of the voltage source type valve group unit to isolate the voltage source converter 2. The voltage source converter 2 is now taken out of operation. The rectification station 27 is matched with the inversion station 28 to exit the power grid commutation converter 1 on line.
The second exit method is: controlling the trigger angle of the power grid commutation converter to be 90 degrees so as to control the direct-current voltage of the power grid commutation converter 1 to be zero; then, a third bypass switch 3 and a first bypass switch 4 of the current source type valve group unit are closed, and after the third bypass switch and the first bypass switch are closed, the trigger angle of the power grid phase-change converter 1 is controlled to be 164 degrees to realize phase shifting of the power grid phase-change converter 1; disconnecting a first valve bank switch 5 of the current source type valve bank unit, separating a third bypass switch 3 of the current source type valve bank unit, closing a first bus switch 12 of the current source type valve bank unit, and connecting the power grid phase-change converter 1 and the voltage source converter 2 in parallel; controlling the power grid commutation converter 1 to remove phase shift, transferring direct current power from the voltage source converter 2 to the power grid commutation converter 1, and controlling the voltage source converter 2 to be locked; and opening the second valve group switch 9 or/and the second bus switch 10 of the voltage source type valve group unit to isolate the voltage source converter 2. At this point the voltage source converter 2 is taken out of operation. The rectification station 27 is matched with the inversion station 28 to exit the power grid commutation converter 1 on line.
In order to prevent the direct current transmission system from being locked due to the fact that a direct current line or an alternating current line fails when the voltage source converter 2 is connected in parallel to the grid commutation converter 1, optionally, a direct current circuit breaker with a disconnected direct current fault current is added between the voltage source converter 2 and the current limiting reactor 11, or a direct current circuit breaker with a disconnected direct current fault current is adopted as the first bus switch 12, or a diode valve bank for blocking the reverse current of the voltage source converter 2 is connected in series between the first bus switch 12 of the hybrid direct current converter on the inversion side and the voltage source converter 2, and the cathode of the diode valve bank and the anode of the voltage source converter are a common connecting end or the anode of the diode valve bank and the cathode of the voltage source converter are a common connecting end. Note that the reverse current of the voltage source converter 2 in the hybrid dc converter on the inverter side flows from the negative pole to the positive pole of the voltage source converter 2.
Fig. 8 is an online exit device for a hybrid dc converter according to an embodiment of the present application, configured to implement online exit of the hybrid dc converter. Comprises a detection unit 34 and a control unit 35.
The detection unit 34 is configured to detect a first direct current voltage, a first direct current, a first unlock signal, a first lock signal, and a first operation signal of the current source type valve block unit, detect a second direct current voltage, a second direct current, a second unlock signal, a second lock signal, and a second operation signal of the voltage source type valve block unit, and detect a position of the first valve block switch 5, the first bus switch 12, the first bypass switch 4, the second valve block switch 9, or the second bus switch 10.
The control unit 35 is configured to control the voltage source converter to exit when the power grid commutation converter and the voltage source converter both have an unlocking signal and an operating signal and receive an instruction from an operator to exit the voltage source converter.
The first control strategy is: a command to block the grid commutated converter 1 is issued. A command is issued to close the first bypass switch 4 of the current source valve group unit and a command is issued to open the first valve group switch 5 of the current source valve group unit when it is detected that the first bypass switch 4 is in the closed position. When detecting that the first valve group switch 5 of the current source valve group unit is in the open position, a command is issued to close the first bus switch 12 of the current source valve group unit. When detecting that the first bus switch 12 of the current source type valve group unit is located at the closed position, the power grid phase-change converter 1 and the voltage source converter 2 are connected in parallel. And unlocking the power grid phase-change converter 1, controlling the direct current power to be transferred from the voltage source converter 2 to the power grid phase-change converter 1, controlling the voltage source converter to be locked or controlling the direct current of the voltage source converter to be equal to or less than the minimum current value, sending a command of opening a second valve group switch 9 of the voltage source type valve group unit, and when detecting that the second valve group switch 9 of the voltage source type valve group unit is positioned in a split position, exiting the voltage source converter 2.
The second control strategy is: and controlling the direct-current voltage of the power grid commutation converter 1 to be zero. Sending a command of closing a first bypass switch 4 of the current source type valve bank unit, and controlling the phase shift of the power grid phase-change converter 1 when detecting that the first bypass switch 4 is in an on position; a command is issued to open the first block switch 5 of the current source type block unit. When detecting that the first valve block switch 5 of the current source valve block unit is in the open position, a command to close the first bus switch 12 of the current source valve block unit is issued. When detecting that the first bus switch 12 of the current source type valve group unit is located at the closed position, the power grid phase-change converter 1 and the voltage source converter 2 are connected in parallel. And releasing the phase shift of the power grid commutation converter 1, controlling the direct current power to be transferred from the voltage source converter 2 to the power grid commutation converter 1, controlling the voltage source converter to be locked or controlling the direct current of the voltage source converter to be equal to or less than the minimum current value, sending a command of opening the second valve group switch 9 of the voltage source type valve group unit, and when detecting that the second valve group switch 9 of the voltage source type valve group unit is positioned separately, the voltage source converter 2 exits.
The converter online exit circuit, the exit method and the exit device are used for online exit of a voltage source converter of a hybrid direct current converter, and are particularly suitable for voltage source converters with narrow direct current voltage regulation range or incapable of regulating direct current voltage to zero voltage.
The foregoing embodiments have been described in detail to illustrate the principles and implementations of the present application, and the foregoing embodiments are only used to help understand the method and its core idea of the present application. Based on the idea of the present application, a person skilled in the art can make changes or modifications based on the specific embodiments and application scope of the present application. In view of the above, the description should not be taken as limiting the application.
Claims (9)
1. An online exit method for a hybrid direct current converter valve bank is applied to an online exit circuit for a hybrid direct current converter valve bank, the hybrid direct current converter comprises a current source type valve bank unit and a voltage source type valve bank unit which are connected in series, the current source type valve bank unit comprises a power grid commutation converter, the voltage source type valve bank unit comprises a voltage source converter, and the circuit comprises:
the first valve bank switch is used for connecting the power grid commutation converter and the voltage source type valve bank unit;
the first bus switch is used for connecting the power grid commutation converter with a direct-current bus or a neutral bus;
a first bypass switch connected in parallel with a series circuit of the first bank switch and the grid commutation converter;
a second bank switch or a second bus switch for connecting the voltage source converter with the current source valve bank unit; the second bus switch is used for connecting the voltage source converter and the direct current bus or the neutral bus;
when the grid commutation converter and the voltage source converter operate simultaneously and the voltage source converter needs to be quitted, the method comprises the following steps:
blocking the grid commutation converter and closing the first bypass switch; or controlling the direct-current voltage of the power grid commutation converter to be zero, closing the first bypass switch, and then controlling the phase shift of the power grid commutation converter;
connecting the grid commutation converter and the voltage source converter in parallel through switch conversion;
unlocking the power grid commutation converter or removing the phase shift of the power grid commutation converter;
transferring direct current power from the voltage source converter to the grid commutated converter;
controlling the voltage source converter to be locked or controlling the direct current of the voltage source converter to be equal to or less than the minimum current value;
isolating the voltage source converter.
2. The method of claim 1, wherein said controlling said grid commutated converter dc voltage to be zero comprises:
and controlling the trigger angle of the power grid phase-change converter to be between 85 and 95 degrees so as to control the direct-current voltage of the power grid phase-change converter to be 0.
3. The method of claim 1, wherein the controlling the grid commutated converter phase shifting comprises:
and controlling the firing angle of the grid commutation converter to be between 120 and 180 degrees so as to control the phase shift of the grid commutation converter.
4. The method of claim 1, wherein the switching comprises:
and opening the first valve group switch and closing the first bus switch.
5. The method of claim 4, if the current source valve block unit includes a third bypass switch, wherein,
before said closing said first bypass switch, further comprising: closing the third bypass switch;
before closing the first bus bar switch, the method further comprises: separating the third bypass switch.
6. The method of claim 1, wherein the first bus switch has an auxiliary resistor connected across it, and wherein closing the first bus switch further comprises:
putting the auxiliary resistor;
when the current flowing through the auxiliary resistor is zero or a minimum value, closing the first bus switch;
and cutting off the auxiliary resistor after the first bus switch is determined to be closed.
7. The method of claim 1, the isolating the voltage source converter comprising:
disconnecting the second bank switch or the second bus switch.
8. The utility model provides an online withdrawing device of mixed DC converter valves, uses at mixed DC converter valves online withdrawing circuit, mixed DC converter includes series connection's current source type valves unit and voltage source type valves unit, current source type valves unit includes electric wire netting commutation converter, voltage source type valves unit includes voltage source converter, wherein, the circuit includes:
the first valve bank switch is used for connecting the power grid commutation converter and the voltage source type valve bank unit;
the first bus switch is used for connecting the power grid commutation converter with a direct-current bus or a neutral bus;
a first bypass switch connected in parallel with a series circuit of the first group valve switch and the grid commutation converter;
a second bank switch or a second bus switch for connecting the voltage source converter with the current source valve bank unit; the second bus switch is used for connecting the voltage source converter and the direct current bus or the neutral bus;
when the power grid commutation converter and the voltage source converter operate simultaneously and need to quit the voltage source converter, the device comprises:
a detection unit for detecting a first direct current voltage, a first direct current, a first unlock signal, a first lock signal, and a first operation signal of the current source type valve group unit, detecting a second direct current voltage, a second direct current, a second unlock signal, a second lock signal, and a second operation signal of the voltage source type valve group unit, and detecting positions of the first valve group switch, the first bus switch, the first bypass switch, the second valve group switch, or the second bus switch;
the control unit is used for controlling the power grid commutation converter to be locked and controlling the first bypass switch to be closed; or the direct-current voltage of the power grid commutation converter is controlled to be zero, the first bypass switch is closed, and then the phase shift of the power grid commutation converter is controlled; connecting the grid commutation converter and the voltage source converter in parallel through switch conversion; unlocking a power grid phase-change converter or removing the phase shift of the power grid phase-change converter; transferring direct current power from the voltage source converter to the grid commutated converter; controlling the voltage source converter to be locked or controlling the direct current of the voltage source converter to be equal to or less than the minimum current value; disconnecting the second bank switch or the second bus switch, isolating the voltage source converter.
9. The apparatus of claim 8, if the current source valve block unit comprises a third bypass switch, wherein the control unit controls closing of the third bypass switch before closing of the first bypass switch; the control unit controls to open the third bypass switch before closing the first bus switch.
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| CN201911095357.1A CN112787347B (en) | 2019-11-11 | 2019-11-11 | Online exit circuit, exit method and exit device for hybrid direct-current converter valve bank |
| PCT/CN2020/127904 WO2021093746A1 (en) | 2019-11-11 | 2020-11-10 | Hybrid direct-current converter inline ejection circuit, ejection method, and ejection apparatus |
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| CN201911095357.1A CN112787347B (en) | 2019-11-11 | 2019-11-11 | Online exit circuit, exit method and exit device for hybrid direct-current converter valve bank |
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| CN108683207A (en) * | 2018-05-28 | 2018-10-19 | 南京南瑞继保电气有限公司 | A kind of mixed DC transverter valve group puts into circuit and input method and device online |
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| CN108683207A (en) * | 2018-05-28 | 2018-10-19 | 南京南瑞继保电气有限公司 | A kind of mixed DC transverter valve group puts into circuit and input method and device online |
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