CN108418237B - Method and device for controlling inter-station communication fault of multi-terminal direct-current power transmission system - Google Patents
Method and device for controlling inter-station communication fault of multi-terminal direct-current power transmission system Download PDFInfo
- Publication number
- CN108418237B CN108418237B CN201810178336.5A CN201810178336A CN108418237B CN 108418237 B CN108418237 B CN 108418237B CN 201810178336 A CN201810178336 A CN 201810178336A CN 108418237 B CN108418237 B CN 108418237B
- Authority
- CN
- China
- Prior art keywords
- converter
- current
- voltage
- direct current
- direct
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- 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]
Abstract
The invention discloses a method and a device for controlling communication faults between multi-terminal direct current transmission system stations, which are used for realizing power coordination control during the communication faults between the multi-terminal direct current transmission system stations, and specifically comprise the following steps: when the current converter at the rectifying side of the multi-terminal direct-current transmission system and the current converter at the inverting side have communication faults, the inverting side reduces direct-current voltage operation, when the inverting side detects that direct current is larger than rated current or overload allowable current, the direct-current voltage operation is improved, and meanwhile, the rectifying side adopts a high-voltage current limiting function to limit the direct current, so that the current converter at the inverting side is prevented from overflowing, and the reliable operation of the multi-terminal direct-current transmission system is ensured. The technical scheme can effectively avoid locking the whole multi-terminal direct current system when the communication between the multi-terminal direct current system stations fails, thereby reducing the impact on an alternating current power grid and improving the stability of the system.
Description
Technical Field
The invention belongs to the field of high-voltage direct-current power transmission, and particularly relates to a method and a device for controlling communication faults between stations of a multi-terminal direct-current power transmission system.
Background
A multi-terminal direct current (MTDC) transmission system refers to a dc transmission system that includes 3 or more converter stations. Compared with two-end direct current transmission, the multi-end direct current transmission provides a more economical and flexible transmission mode, can realize multi-power supply and multi-drop power receiving, and has better development potential and application prospect in China. From the control protection point of view, the generalized multi-terminal dc transmission system also refers to a dc transmission system with 2 or more converters connected in parallel on the rectifying side or the inverting side.
The structure mode of the multi-terminal direct current transmission system is basically divided into parallel connection and series connection. The power regulation range of each converter station under the parallel structure is large, the extension of the converter stations is flexible, the whole system is convenient to be insulated and matched, the running economy is high, and the method is a preferred mode of the multi-terminal direct current transmission project at present.
In the parallel multi-terminal dc system, because a plurality of rectifier-side converter stations or a plurality of inverter-side converter stations exist at the same time, a multi-terminal controller is usually required to be provided to communicate with each station controller, so as to realize coordinated control among the multi-terminal dc stations and balance power or current commands among the converter stations. Each converter station and the multi-end controller need to be connected through an inter-station communication channel, and whether the inter-station communication is normal or not has great influence on the stable operation of the whole system.
In a multi-terminal direct current (MTDC) transmission system, the types of converter stations may comprise a conventional grid commutated converter (LCC) type and a Voltage Source Converter (VSC) type. Among them, a multi-terminal dc system including only the LCC-type converter station is referred to as a multi-terminal conventional dc system, a multi-terminal dc system including both the LCC-type converter station and the VSC-type converter station is referred to as a multi-terminal hybrid dc system, and a multi-terminal dc system including only the VSC-type converter station is referred to as a multi-terminal flexible dc system.
Fig. 1 shows a typical structure of a parallel four-terminal conventional dc transmission system main circuit. The four-terminal direct-current transmission system comprises two rectifying stations and two inverter stations, namely a rectifying station I1, a rectifying station II 2, an inverter station I3 and an inverter station II 4. The four converter stations are all LCC type converter stations, different converter stations are connected into different alternating current power grids 5, and the different converter stations are connected in parallel through direct current circuits 6. Each converter station comprises two symmetrical poles, and a two-pole neutral bus 15 is connected with a grounding electrode 17 through a grounding electrode lead 16. Each pole comprises a high-side converter 13 and a low-side converter 14 in the form of a six-pulse or twelve-pulse bridge circuit, which are connected to the ac power grid 5 by a high-side converter transformer 11 and a low-side converter transformer 12, respectively.
Fig. 2 shows a main loop structure of a parallel three-terminal hybrid dc power transmission system. The three-terminal hybrid direct-current transmission system comprises a rectifying station and two inverter stations, wherein the rectifying station I1 and the inverter station I3 are both LCC type converter stations, and the inverter station II 7 is a VSC type converter station. Each converter station is connected to different alternating current networks 5, and the different converter stations are connected in parallel through direct current lines 6. The configuration of the LCC converter station is the same as that in fig. 1, each pole of the VSC converter station is composed of a modular multi-level converter (MMC) 71, and the MCC converter is connected to the ac grid 5 through a junction transformer 72.
Fig. 3 shows a hybrid dc converter with a grid commutated converter 31 connected in series with a voltage source converter on the inverting side, wherein the voltage source converter is located in a series circuit comprising two parallel modular multilevel voltage source converters 71 and 73. The grid commutated converter 31, the modular multilevel voltage source converter 71 and the modular multilevel voltage source converter 73 are connected to the ac grid 5 via a converter transformer 32, a tie converter 72 and a tie converter 74, respectively. The grid commutation converter 31, the modular multilevel voltage source converter 71 and the modular multilevel voltage source converter 73 can be distributed in the same inversion station, or the grid commutation converter 31, the modular multilevel voltage source converter 71 are in one inversion station, the modular multilevel voltage source converter 73 is in another inversion station, or the grid commutation converter 31 is in one inversion station, the modular multilevel voltage source converter 71 and the modular multilevel voltage source converter 73 are in another inversion station, or the three are distributed in three different inversion stations.
When the multi-terminal direct current system normally operates, the balance control of power or current among different stations is realized through multi-terminal control of a system layer. Fig. 4 and 5 are structural diagrams of two typical configurations of parallel four-terminal direct-current transmission system inter-station communication. In fig. 4, a four-terminal controller is configured in both the rectifier station I1 and the inverter station I3, wherein the four-terminal controller configured in the rectifier station I1 is a main controller, and the four-terminal controller configured in the inverter station I3 is a standby controller. The four converter stations are connected with the two four-terminal controls through the inter-station communication channels, and the two four-terminal controls are also connected through inter-station communication. When the communication between stations is normal, the four-terminal main controller of the rectifier station 1 simultaneously receives state values of voltage, current, power and the like of the two rectifier stations and the two inverter stations, and simultaneously each converter station issues control instructions of voltage, current and the like, so that the balance and stable control of the whole multi-terminal direct current are realized. In fig. 5, two converter stations are interconnected through inter-station communication channels, state information such as voltage, current, power and the like is transmitted among the stations, and meanwhile, a multi-terminal coordination controller is arranged in each of the four converter stations, so that only the multi-terminal coordination control of one station is in an effective state during actual operation, and the multi-terminal coordination controls of other stations are in a standby state.
Generally, two rectifying side converter stations in four-terminal direct current operate in a current or power control mode, the inverter side converter station with the larger capacity operates in a voltage control mode, and the inverter side converter station with the smaller capacity operates in a current or power control mode. When a certain converter station is locked and quits operation due to faults, the multi-terminal control can timely detect the operation state of the converter station, and simultaneously timely adjust the operation modes and voltage and current control instructions of other converter stations, so that rebalance control of the whole multi-terminal direct current system is realized. According to the operation example of the inversion side voltage control station fault blocking exit, in the four-terminal direct current normal operation process, when the inversion side voltage control station exits due to fault blocking, the multi-terminal control firstly adjusts the operation mode of the other inversion station from a current control mode to a voltage control mode, and therefore the stability of direct current voltage is guaranteed. Meanwhile, current instructions of the two converter stations on the rectifying side are adjusted in time according to the transmission capacity of the inverter station, so that the balance of power at the transmitting end and the receiving end is ensured, and the inverter station is prevented from being in an overload state for a long time.
Because the mutual distance between the converter stations is far, the communication channel between the stations is long, and the communication fault between the stations is difficult to avoid. When communication channel failure occurs between stations, communication between the inverter side converter station and the rectifier side converter station is lost, the multi-terminal control cannot detect the operation state of the inverter station in real time, and correct control instructions cannot be transmitted to the rectifier station. At this time, the multi-end controller can only quit operation, and each converter station is in an independent operation state. In the meantime, if a certain inverter side converter station is locked due to a fault, overload operation of other inverter side converter stations which normally operate will be caused. At present, in order to avoid a long-term overload state of a converter station on an inverter side, a common control strategy is that when communication loss between the converter station and a multi-terminal controller is detected, the converter station is locked if overload capacity of a converter of the converter station is exceeded, and the multi-terminal converter coordinately controls operation states of other normally-operating converter stations. When communication between all the inverter side converter station stations is lost, the whole multi-terminal direct-current transmission system can be locked finally.
When communication between the inversion side converter stations is lost, if the whole multi-terminal direct-current transmission system is locked due to overload of the inversion side converter stations, large impact is brought to a transmission receiving end alternating-current system, and stable operation of an alternating-current power grid is affected.
Disclosure of Invention
The invention aims to provide a method for controlling communication faults between stations of a multi-terminal direct-current transmission system, which is characterized in that when the communication faults of a converter station at a rectifying side and a converter station at an inverting side of the multi-terminal direct-current transmission system occur, the active locking of the whole multi-terminal direct-current transmission system or the locking of the whole multi-terminal direct-current transmission system caused by the locking of a certain receiving-end converter is avoided by the active adjustment of a converter at the rectifying side and a converter at the inverting side of a transmitting and receiving end; meanwhile, the control device under the communication fault between the stations of the multi-terminal direct-current transmission system is used for controlling the multi-terminal direct-current converter.
In order to achieve the purpose, the invention adopts the technical scheme that: a method for controlling a multi-terminal direct-current transmission system under an inter-station communication fault is used for the multi-terminal direct-current transmission system, when a current converter on a rectifying side of the multi-terminal direct-current transmission system and a current converter on an inverting side have communication faults, the inverting side reduces direct-current voltage to operate, when the inverting side detects that direct current or alternating current flowing through the current converter is larger than rated current or overload allowable current, the inverting side improves the direct-current voltage to operate, and meanwhile, the rectifying side adopts a high-voltage current limiting function to limit the direct current until the direct current or the alternating current is reduced to the rated current or the overload allowable current.
The inversion side of the multi-terminal direct current transmission system at least comprises two inversion stations, and two or more inversion stations share the same direct current bus; or the inversion side at least comprises two parallel converters; or at least one series branch on the inversion side at least comprises two parallel converters.
The communication fault of the converter on the rectifying side and the converter on the inverting side of the multi-terminal direct current transmission system is that all the converters on the rectifying side lose communication with all the converters on the inverting side, or part of the converters on the inverting side lose communication with all the converters on the rectifying side, or part of the converters on the rectifying side lose communication with all the converters on the inverting side, or part of the converters on the rectifying side lose communication with part of the converters on the inverting side.
The direct current voltage reduction at the inverting side is realized by reducing the direct current voltage of a converter for controlling the direct current voltage at the inverting side, reducing the phase voltage at the valve side or increasing the arc extinguishing angle of the converter by changing a converter transformer tap of the converter for a power grid phase change converter, and reducing the phase voltage at the valve side or controlling the voltage of a voltage source converter or reducing the input number of sub-modules or reducing the voltage of the sub-modules by changing a connecting transformer tap of the converter for a voltage source converter; the inverter side is used for improving direct current voltage, the inverter side is used for controlling a converter of the direct current voltage to improve the direct current voltage, for a power grid phase change converter, valve side phase voltage is improved or the arc extinguishing angle of the converter is reduced by changing a converter transformer tap of the converter, for a voltage source converter, the valve side phase voltage is improved by changing a connecting transformer tap of the converter, or the voltage of the voltage source converter is controlled, or the input number of sub-modules is increased, or the voltage of the sub-modules is increased.
The inverter side detects that the direct current or the alternating current flowing through the inverter is larger than the rated current or the overload allowable current, namely the direct current flowing through the inverter is larger than the rated direct current or the overload allowable direct current, or the alternating current flowing through the inverter is larger than the rated alternating current or the overload allowable alternating current, and the direct current or the alternating current is caused to be overcurrent by the fact that the inverter on the inverter side locks or a rectifying station boosts the direct current power; when the overload allowable current is the operation of the converter, considering the overcurrent and overvoltage level of main loop equipment, different overload allowable current levels correspond to different allowable operation time according to the maximum operation current allowed by the temperature of a valve hall, the existence of redundant cooling and the temperature of inlet and outlet water. The inversion side detects that the direct current or alternating current flowing through the converter is larger than the rated current or the overload allowable current, and a delay opening link is adopted for triggering.
The rectification side adopts a high-voltage current-limiting function, and reduces a direct current instruction when detecting that the direct current voltage is higher than the allowed direct current voltage under the condition of communication fault; the higher the dc voltage, the smaller the dc current command. The allowable dc voltage is preset by the converter on the rectifying side, is a constant value or a linear function of the dc current, and is determined by the converter voltage on the inverting side and the line voltage drop. The above-described high voltage current limiting function is introduced in the event of a communication failure between stations.
If the converter on the inverting side of the fault latch is in a current control mode or a power control mode before the latch, the converter on the inverting side in the voltage control mode immediately increases the direct current voltage of the system after detecting that the direct current or the alternating current of the station is larger than the rated current or the overload allowable current, so that the overload signal of the converter on the inverting side is transmitted to the converter on the rectifying side through the direct current voltage; after detecting the rise of the direct current voltage, the converter at the rectifying side immediately enters a high-voltage current limiting control mode to reduce the direct current of the converter at the rectifying side; if the converter on the inversion side of the fault lock is in the voltage control mode before the lock, the converter on the inversion side in the current control mode or the power control mode is immediately converted into the voltage control mode to carry out direct current boost control.
In addition, the present invention also provides a control device under an inter-station communication fault of a multi-terminal dc power transmission system, which is used for the multi-terminal dc power transmission system, and is characterized in that the device comprises a detection unit and a control unit, wherein:
a detection unit for detecting direct current, direct voltage, inter-station communication signals, a converter transformer or a coupling transformer tap;
and the control unit is used for controlling the converter at the inverting side to reduce the direct-current voltage to operate when detecting the communication faults of the converter at the rectifying side and the converter at the inverting side of the multi-terminal direct-current transmission system, and improving the direct-current voltage to operate when the converter at the inverting side detects that the direct current or the alternating current flowing through the converter is greater than the rated current or the overload allowable current of the converter, and meanwhile, the converter at the rectifying side adopts a high-voltage current limiting function to limit the direct current until the direct current or the alternating current is reduced to the rated current or the overload allowable current.
The inversion side of the multi-terminal direct current transmission system at least comprises two inversion stations, and two or more inversion stations share the same direct current bus; or the inversion side at least comprises two parallel converters; or at least one series branch on the inversion side at least comprises two parallel converters.
The communication fault of the converter on the rectifying side and the converter on the inverting side of the multi-terminal direct current transmission system is that all the converters on the rectifying side lose communication with all the converters on the inverting side, or part of the converters on the inverting side lose communication with all the converters on the rectifying side, or part of the converters on the rectifying side lose communication with all the converters on the inverting side, or part of the converters on the rectifying side lose communication with part of the converters on the inverting side.
The direct current voltage reduction at the inverting side is realized by reducing the direct current voltage of a converter for controlling the direct current voltage at the inverting side, reducing the phase voltage at the valve side or increasing the arc extinguishing angle of the converter by changing a converter transformer tap of the converter for a power grid phase change converter, and reducing the phase voltage at the valve side or controlling the voltage of a voltage source converter or reducing the input number of sub-modules or reducing the voltage of the sub-modules by changing a connecting transformer tap of the converter for a voltage source converter; the inverter side is used for improving direct current voltage, the inverter side is used for controlling a converter of the direct current voltage to improve the direct current voltage, for a power grid phase change converter, valve side phase voltage is improved or the arc extinguishing angle of the converter is reduced by changing a converter transformer tap of the converter, for a voltage source converter, the valve side phase voltage is improved by changing a connecting transformer tap of the converter, or the voltage of the voltage source converter is controlled, or the input number of sub-modules is increased, or the voltage of the sub-modules is increased.
The direct current voltage is reduced by the inverter side, the direct current voltage of the system is actively reduced by the inverter side, and the reduction amplitude of the direct current voltage is preset by the system; in other converters in the current control mode or the power control mode, the direct current instruction value or the direct current power instruction value is kept unchanged in the direct current voltage reduction process.
The inverter side detects that the direct current or the alternating current flowing through the inverter is larger than the rated current or the overload allowable current, namely the direct current flowing through the inverter is larger than the rated direct current or the overload allowable direct current, or the alternating current flowing through the inverter is larger than the rated alternating current or the overload allowable alternating current, and the direct current or the alternating current is caused to be overcurrent by the fact that the inverter on the inverter side locks or a rectifying station boosts the direct current power; when the overload allowable current is the operation of the converter, considering the overcurrent and overvoltage level of main loop equipment, different overload allowable current levels correspond to different allowable operation time according to the maximum operation current allowed by the temperature of a valve hall, the existence of redundant cooling and the temperature of inlet and outlet water.
The rectification side adopts a high-voltage current-limiting function, and reduces a direct current instruction when detecting that the direct current voltage is higher than the allowed direct current voltage under the condition of communication fault; the higher the dc voltage, the smaller the dc current command.
If the converter on the inverting side of the fault latch is in a current control mode or a power control mode before the latch, the converter on the inverting side in the voltage control mode immediately increases the direct current voltage of the system after detecting that the direct current or the alternating current of the station is larger than the rated current or the overload allowable current, so that the overload signal of the converter on the inverting side is transmitted to the converter on the rectifying side through the direct current voltage; after detecting the rise of the direct current voltage, the converter at the rectifying side immediately enters a high-voltage current limiting control mode to reduce the direct current of the converter at the rectifying side; if the converter on the inversion side of the fault lock is in the voltage control mode before the lock, the converter on the inversion side in the current control mode or the power control mode is immediately converted into the voltage control mode to carry out direct current boost control.
After the scheme is adopted, compared with the prior art, when the communication between the converter station at the rectifying side and the converter station at the inverting side of the multi-terminal direct-current transmission system has a fault, the inverting side operates by reducing the direct-current voltage, so that the control capability of the inverting station on the overload current is effectively improved on the one hand, and on the other hand, when the converter station at the inverting side is locked and the converters of other operating converter stations detect that the direct current is greater than the rated current, the overload signals of the converters are transmitted to the rectifying side by improving the direct-current voltage to operate, so that the rectifying side limits the direct current by adopting the high-voltage current-limiting function, the locking of the inverting side due to the exhaustion of the overload capability is avoided, and the shutdown of the whole multi-terminal direct-current transmission system is avoided.
Drawings
Fig. 1 is a schematic diagram of a main loop of a parallel four-terminal direct-current transmission system with an LCC converter station on both a rectification side and an inversion side;
fig. 2 is a schematic diagram of a main loop of a parallel three-terminal direct-current transmission system with an inversion side containing both LCC and VSC type converter stations;
FIG. 3 is a schematic diagram of a main loop of a direct current transmission system formed by a hybrid direct current converter formed by connecting an LCC and a VSC type converter in series on an inversion side;
FIG. 4 is a schematic structural diagram of a first inter-station communication mode of a parallel four-terminal DC power transmission system
FIG. 5 is a schematic structural diagram of a second inter-station communication mode of a parallel four-terminal DC power transmission system
FIG. 6 is a flow chart of a control method under inter-station communication failure of the multi-terminal direct current transmission system of the present invention;
fig. 7 is a control characteristic diagram of a rectifier side converter station in the case of control under an inter-station communication fault of the multi-terminal direct-current transmission system of the present invention;
FIG. 8 is a schematic structural view of a control device of the present invention;
reference numerals: 1. LCC type rectifier station I; 11. a high-end converter transformer; 12. a low-side converter transformer; 13. a high-side converter; 14. a low-side inverter; 15. a polar neutral bus; 16. a ground lead; 17. a ground electrode; 2. LCC type rectifier station II; 3. LCC type inverter station I; 31. a power grid commutation converter; 32. a converter transformer; 4. LCC type inverter station II; 5. an alternating current grid; 6. a direct current line; 7. a VSC type inversion station II; 71. a modular multilevel voltage source converter; 72. connecting a transformer; 73. a modular multilevel voltage source converter; 74. connecting a transformer; 8. a diode valve; 9. controlling device under the communication fault between the multi-terminal direct current transmission system stations; 91. a detection unit; 92. a control unit.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Fig. 6 shows a control method for inter-station communication failure of a multi-terminal direct-current power transmission system provided by the invention. When the communication between the stations is normal, the balance control of the system is realized among the converter stations through a multi-terminal controller. When the communication between the inversion side converter or the converter station and the rectification side converter or the converter station is lost, the inversion side voltage control station enters a voltage reduction control mode to actively reduce the direct current voltage of the system, and the reduction amplitude of the direct current voltage is preset by the system, such as the reduction of the rated direct current voltage by 5%; in the other converter stations in the current control mode or the power control mode, the direct current command value or the direct current power command value is kept unchanged in the direct current voltage reduction process. At this time, the whole multi-terminal power transmission system enters a step-down and power-down or step-down and constant-power operation mode, wherein if the step-down is adopted, the power reduction amplitude is the same as the voltage reduction amplitude. The adjustment of the direct-current voltage of the multi-terminal direct-current system is realized by adjusting the arc extinguishing angle of the voltage control station on the inversion side or the tap joint of the converter transformer for the power grid commutation converter. In the actual engineering regulation process, the reactive compensation capability of the inverter station and the regulation capability of the tap joint of the converter transformer need to be considered. Because the arc-quenching angle is adjusted at a speed much faster than that of tap control, the voltage reduction control is usually performed by preferentially adopting a mode of keeping the tap gear of the converter transformer unchanged and increasing the arc-quenching angle on the inversion side; for the voltage source converter, the voltage of a valve side phase is reduced by changing a connecting transformer tap of the converter, or the voltage of the voltage source converter is controlled to be reduced, or the input number of sub-modules is reduced, or the voltage of the sub-modules is reduced. In the actual engineering adjusting process, the investment number of the submodules is preferably reduced.
During inter-station communication faults, the converter on the rectifying side introduces a high voltage current limiting function. If the system has high operating power and a converter on one inversion side is locked and shut down due to a fault, the direct current Id of other inversion stations in normal operation is larger than the rated value IdN or overload allowable current, or the alternating current Iac is larger than the rated value IacN or overload current, so that overload operation occurs. At this time, the inverter side inverter performs boost control, and the rectifier side inverter performs high-voltage current limiting control to reduce the dc current at the rectifier side, thereby reducing the dc power at the rectifier side.
For the parallel four-terminal conventional direct-current transmission system shown in fig. 1, during inter-station communication failure, if an inverter station locked by a failure is in a current control mode before locking, the inverter-side converter station in the voltage control mode immediately raises the direct-current voltage of the system by raising a tap gear or reducing a converter arc-extinguishing angle after detecting that the direct-current of the station is greater than a rated current, so that an overload signal of the inverter-side converter station is transmitted to the rectifier-side converter station through the direct-current voltage. And after detecting the rise of the direct current voltage, the rectification side converter station immediately enters a high-voltage current limiting control mode, so that the direct current of the rectification side converter station is reduced. Finally, the converter stations on the rectifying side and the inverting side will again be adjusted to a stable operating point for operation. And if the inverter station with the fault locking is in the voltage control mode before locking, immediately converting the inverter side converter station in the current control mode into the voltage control mode for direct current boost control.
For the parallel type three-terminal hybrid dc transmission system shown in fig. 2, during an inter-station communication fault, if the inverter station of the fault latch is in the current control mode before the latch, the VSC type converter station performs voltage control. If the inverter side converter station with the fault lock is a VSC type converter station, the inverter side converter station in the current control mode immediately converts the DC current into a voltage control station for DC boost control when detecting that the DC current of the inverter side converter station is larger than the rated current.
For the hybrid dc converter shown in fig. 3 to form a dc transmission system, during inter-station communication failure, if the blocked modular multilevel voltage source converter is in the current control mode before blocking, the voltage control mode modular multilevel voltage source converter will immediately adjust the connecting transformer tap to raise the valve side phase voltage, or raise the voltage of the voltage source converter, or increase the number of the sub-modules to be put in, or increase the sub-module voltage to raise the dc voltage of the system after detecting that the dc current flowing through the converter is greater than the rated dc current or the overload allowable current, or the ac current flowing through the converter is greater than the rated ac current or the overload allowable current, so as to transmit the overload signal of the inverter side converter station to the rectifier side converter station through the dc voltage. And after detecting the rise of the direct current voltage, the rectification side converter station immediately enters a high-voltage current limiting control mode, so that the direct current of the rectification side converter station is reduced. Finally, the converter stations on the rectifying side and the inverting side will again be adjusted to a stable operating point for operation. If the fault-locked modular multilevel voltage source converter is in the voltage control mode before locking, the modular multilevel voltage source converter in the current control mode or the power control mode is immediately converted into the voltage control mode for direct current boost control.
Fig. 7 shows control characteristic curves of the rectifier side converter station before and after an inter-station communication failure. In fig. 7, a characteristic curve 1 is an operation curve of the rectifier side converter station before communication failure between stations, and the curve mainly includes a constant current control curve CD, a low voltage current limiting curve BC, and a minimum current limiting curve AB; the characteristic curve 2 is an operation curve of the rectifier side converter station after communication failure between stations, and mainly comprises a constant current control curve GH, a low-voltage current-limiting curve FG, a minimum current limiting curve EF, a high-voltage current-limiting characteristic curve HJ and a high-voltage minimum current limiting curve JK.
In fig. 7, before the inter-station communication failure, the rectifier side converter operates at an operating point 1 whose voltage is a rated value UdNThe current value is the command value I transmitted by the multi-terminal controllerord(ii) a After the communication fault between stations, the control characteristic curve of the current converter of the rectifier station is wholly translated to the leftThe current side converter operates at an operating point 2 with a voltage value less than the nominal operating value, which is UdoThe current of which is kept at the multi-terminal controller command value Iord. After communication between stations fails, if the inverter side of the converter in the current control mode adopts a method for keeping a direct current instruction constant in the voltage reduction operation process, the reduced power proportion of each converter can be kept the same. During the voltage reduction operation period, after a certain inverter side converter is locked out of operation due to faults, the rectifier side converter adopts a high-voltage current-limiting characteristic curve HJ with the same slope, and the equal proportion coordination of direct current power among different rectifier stations can be realized.
Fig. 8 shows that the present invention further provides a control device 9 under inter-station communication failure of the multi-terminal dc power transmission system, and the schematic structure thereof specifically includes:
(1) a detection unit 91 for detecting a direct current, a direct voltage, an inter-station communication signal, and a tap of the converter transformer;
(2) and the control unit 92 reduces the direct current voltage to operate when the communication fault is detected, improves the direct current voltage to operate when the inversion side detects that the direct current or the alternating current is greater than the rated current or the overload allowable current, and limits the direct current by adopting the high-voltage current limiting function on the rectification side.
In summary, the present invention discloses a method and an apparatus for controlling communication faults between multi-terminal dc power transmission system stations, which are used to implement power coordination control when communication faults between multi-terminal dc power transmission system stations occur. When the communication fault of the rectifying side converter station and the inverting side converter station of the multi-terminal direct current transmission system occurs, the inverter on the inverting side reduces the direct current voltage operation, when the inverting side detects that the direct current or the alternating current flowing through the inverter is larger than the rated current or the overload allowable current, the direct current voltage operation is improved, and meanwhile, the inverter on the rectifying side adopts high-voltage current-limiting control to limit the direct current and prevent the inverter on the inverting side from being in an overload state for a long time, so that the reliable operation of the multi-terminal direct current transmission system is ensured, and the whole multi-terminal direct current transmission system is prevented from being locked.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.
Claims (14)
1. A control method under the communication fault between multi-terminal direct current transmission system stations is used for a multi-terminal direct current transmission system and is characterized in that: when a current converter on the rectifying side of the multi-terminal direct-current transmission system and a current converter on the inverting side have communication faults, the inverting side reduces direct-current voltage to operate, when the inverting side detects that direct current or alternating current flowing through the current converter is larger than rated current or overload allowable current, the inverting side improves the direct-current voltage to operate, and meanwhile, the rectifying side adopts a high-voltage current limiting function to limit the direct current flowing through the current converter on the inverting side until the direct current or the alternating current flowing through the current converter on the inverting side is reduced to the rated current or the overload allowable current;
the direct current voltage is reduced on the inversion side, the direct current voltage is reduced by a converter for controlling the direct current voltage on the inversion side, for a power grid phase change converter, the valve side phase voltage is reduced or the arc extinguishing angle of the converter is increased by changing a converter transformer tap of the converter, for a voltage source converter, the valve side phase voltage is reduced by changing a connecting transformer tap of the converter, or the voltage of the voltage source converter is controlled, or the input number of sub-modules is reduced, or the voltage of the sub-modules is reduced; the inverter side is used for improving direct current voltage, the inverter side is used for controlling a converter of the direct current voltage to improve the direct current voltage, for a power grid phase change converter, valve side phase voltage is improved or the arc extinguishing angle of the converter is reduced by changing a converter transformer tap of the converter, for a voltage source converter, the valve side phase voltage is improved by changing a connecting transformer tap of the converter, or the voltage of the voltage source converter is controlled, or the input number of sub-modules is increased, or the voltage of the sub-modules is increased.
2. The method for controlling under the condition of the inter-station communication fault of the multi-terminal direct-current transmission system according to claim 1, wherein the method comprises the following steps: the inversion side of the multi-terminal direct current transmission system at least comprises two inversion stations, and two or more inversion stations share the same direct current bus; or the inversion side at least comprises two parallel converters; or at least one series branch on the inversion side at least comprises two parallel converters.
3. The method for controlling under the condition of the inter-station communication fault of the multi-terminal direct-current transmission system according to claim 1, wherein the method comprises the following steps: the communication fault of the converter at the rectifying side and the converter at the inverting side of the multi-terminal direct current transmission system is that all the converters at the rectifying side lose communication with all the converters at the inverting side, or part of the converters at the inverting side lose communication with all the converters at the rectifying side, or part of the converters at the rectifying side lose communication with all the converters at the inverting side, or part of the converters at the rectifying side lose communication with part of the converters at the inverting side.
4. The method for controlling under the condition of the inter-station communication fault of the multi-terminal direct-current transmission system according to claim 1, wherein the method comprises the following steps: the direct current voltage is reduced by the inverter side, the direct current voltage of the system is actively reduced by the inverter side, and the reduction amplitude of the direct current voltage is preset by the system; in other converters in the current control mode or the power control mode, the direct current instruction value or the direct current power instruction value is kept unchanged in the direct current voltage reduction process.
5. The method for controlling under the condition of the inter-station communication fault of the multi-terminal direct-current transmission system according to claim 1, wherein the method comprises the following steps: the method comprises the following steps that the inversion side detects that the direct current or the alternating current flowing through the converter is larger than the rated current or the overload allowable current, and the direct current or the alternating current flowing through the converter is larger than the rated direct current or the overload allowable direct current or the alternating current flowing through the converter is larger than the rated alternating current or the overload allowable alternating current; when the overload allowable current is the operation of the converter, considering the overcurrent and overvoltage level of main loop equipment, different overload allowable current levels correspond to different allowable operation time according to the maximum operation current allowed by the temperature of a valve hall, the existence of redundant cooling and the temperature of inlet and outlet water.
6. The method for controlling under the condition of the inter-station communication fault of the multi-terminal direct-current transmission system according to claim 1, wherein the method comprises the following steps: the rectification side adopts a high-voltage current-limiting function, and reduces a direct current instruction when detecting that the direct current voltage is higher than the allowed direct current voltage under the condition of communication fault; the higher the dc voltage, the smaller the dc current command.
7. The method for controlling under the condition of the inter-station communication fault of the multi-terminal direct-current transmission system according to claim 1, wherein the method comprises the following steps: if the converter on the inverting side of the fault latch is in a current control mode or a power control mode before the latch, the converter on the inverting side in the voltage control mode immediately increases the direct current voltage of the system after detecting that the direct current or the alternating current of the station is larger than the rated current or the overload allowable current, so that the overload signal of the converter on the inverting side is transmitted to the converter on the rectifying side through the direct current voltage; after detecting the rise of the direct current voltage, the converter at the rectifying side immediately enters a high-voltage current limiting control mode to reduce the direct current of the converter at the rectifying side; if the converter on the inversion side of the fault lock is in the voltage control mode before the lock, the converter on the inversion side in the current control mode or the power control mode is immediately converted into the voltage control mode to carry out direct current boost control.
8. A control device under communication fault between multi-terminal direct current transmission system stations is used for a multi-terminal direct current transmission system, and is characterized by comprising a detection unit and a control unit, wherein:
a detecting unit for detecting direct current, direct voltage, inter-station communication signals, converter transformer taps or coupling transformer taps;
the control unit is used for controlling the converter at the inverting side to reduce the direct-current voltage to operate when the communication faults of the converter at the rectifying side and the converter at the inverting side of the multi-terminal direct-current transmission system are detected, and improving the direct-current voltage to operate when the converter at the inverting side detects that the direct current or the alternating current flowing through the converter is greater than the rated current or the overload allowable current of the converter, and meanwhile, the converter at the inverting side adopts a high-voltage current limiting function to limit the direct current flowing through the converter at the inverting side until the direct current or the alternating current flowing through the converter at the inverting side is reduced to the rated current or the overload allowable current;
the inverter side converter reduces direct current voltage, the inverter side converter controls the direct current voltage to reduce the direct current voltage, for a power grid phase change converter, valve side phase voltage is reduced or the arc extinguishing angle of the converter is increased by changing a converter transformer tap of the converter, for a voltage source converter, the valve side phase voltage is reduced or the voltage of the voltage source converter is controlled or the input number of sub-modules is reduced or the voltage of the sub-modules is reduced by changing a connecting transformer tap of the converter; the inverter side converter improves direct current voltage, the inverter side converter controls the direct current voltage to improve the direct current voltage, for a power grid phase change converter, valve side phase voltage is improved or the arc extinguishing angle of the converter is reduced by changing a converter transformer tap of the converter, for a voltage source converter, the valve side phase voltage is improved by changing a connecting transformer tap of the converter, or the voltage of the voltage source converter is controlled, or the input number of sub-modules is increased, or the voltage of the sub-modules is increased.
9. The apparatus according to claim 8, wherein the apparatus is configured to control under a fault of inter-station communication in the multi-terminal dc power transmission system: the inversion side of the multi-terminal direct current transmission system at least comprises two inversion stations, and two or more inversion stations share the same direct current bus; or the inversion side at least comprises two parallel converters; or at least one series branch on the inversion side at least comprises two parallel converters.
10. The apparatus according to claim 8, wherein the apparatus is configured to control under a fault of inter-station communication in the multi-terminal dc power transmission system: the communication fault of the converter at the rectifying side and the converter at the inverting side of the multi-terminal direct current transmission system is that all the converters at the rectifying side lose communication with all the converters at the inverting side, or part of the converters at the inverting side lose communication with all the converters at the rectifying side, or part of the converters at the rectifying side lose communication with all the converters at the inverting side, or part of the converters at the rectifying side lose communication with part of the converters at the inverting side.
11. The apparatus according to claim 8, wherein the apparatus is configured to control under a fault of inter-station communication in the multi-terminal dc power transmission system: the inverter on the inversion side reduces the direct-current voltage, the direct-current voltage of the system is actively reduced on the inversion side, and the reduction amplitude of the direct-current voltage is preset by the system; in other converters in the current control mode or the power control mode, the direct current instruction value or the direct current power instruction value is kept unchanged in the direct current voltage reduction process.
12. The apparatus according to claim 8, wherein the apparatus is configured to control under a fault of inter-station communication in the multi-terminal dc power transmission system: the method comprises the following steps that the inversion side detects that the direct current or the alternating current flowing through the converter is larger than the rated current or the overload allowable current, and the direct current or the alternating current flowing through the converter is larger than the rated direct current or the overload allowable direct current or the alternating current flowing through the converter is larger than the rated alternating current or the overload allowable alternating current; when the overload allowable current is the operation of the converter, considering the overcurrent and overvoltage level of main loop equipment, different overload allowable current levels correspond to different allowable operation time according to the maximum operation current allowed by the temperature of a valve hall, the existence of redundant cooling and the temperature of inlet and outlet water.
13. The apparatus according to claim 8, wherein the apparatus is configured to control under a fault of inter-station communication in the multi-terminal dc power transmission system: the converter on the rectifying side adopts a high-voltage current-limiting function, and reduces a direct current instruction when the rectifying side detects that the direct current voltage is higher than the allowed direct current voltage under the condition of communication fault; the higher the dc voltage, the smaller the dc current command.
14. The apparatus according to claim 8, wherein the apparatus is configured to control under a fault of inter-station communication in the multi-terminal dc power transmission system: if the converter on the inverting side of the fault latch is in a current control mode or a power control mode before the latch, the converter on the inverting side in the voltage control mode immediately increases the direct current voltage of the system after detecting that the direct current or the alternating current of the station is larger than the rated current or the overload allowable current, so that the overload signal of the converter on the inverting side is transmitted to the converter on the rectifying side through the direct current voltage; after detecting the rise of the direct current voltage, the converter at the rectifying side immediately enters a high-voltage current limiting control mode to reduce the direct current of the converter at the rectifying side; if the converter on the inversion side of the fault lock is in the voltage control mode before the lock, the converter on the inversion side in the current control mode or the power control mode is immediately converted into the voltage control mode to carry out direct current boost control.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810178336.5A CN108418237B (en) | 2018-03-05 | 2018-03-05 | Method and device for controlling inter-station communication fault of multi-terminal direct-current power transmission system |
| PCT/CN2019/076737 WO2019170040A1 (en) | 2018-03-05 | 2019-03-01 | Control method and device for multi-terminal direct current power transmission system during inter-station communication fault |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810178336.5A CN108418237B (en) | 2018-03-05 | 2018-03-05 | Method and device for controlling inter-station communication fault of multi-terminal direct-current power transmission system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108418237A CN108418237A (en) | 2018-08-17 |
| CN108418237B true CN108418237B (en) | 2021-11-12 |
Family
ID=63129986
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810178336.5A Active CN108418237B (en) | 2018-03-05 | 2018-03-05 | Method and device for controlling inter-station communication fault of multi-terminal direct-current power transmission system |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN108418237B (en) |
| WO (1) | WO2019170040A1 (en) |
Families Citing this family (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108418237B (en) * | 2018-03-05 | 2021-11-12 | 南京南瑞继保电气有限公司 | Method and device for controlling inter-station communication fault of multi-terminal direct-current power transmission system |
| CN110061509B (en) * | 2019-05-22 | 2020-09-29 | 国家电网有限公司 | On-load voltage regulation control method and system for transformer in flexible direct current system |
| CN110518618B (en) * | 2019-07-30 | 2022-07-22 | 南京南瑞继保电气有限公司 | Unidirectional current protection method and protection device for phase-change converter of direct-current power transmission grid |
| CN110718900B (en) * | 2019-10-12 | 2023-03-28 | 日立能源瑞士股份公司 | Method and apparatus for detecting faults in a hybrid power system |
| CN110829476B (en) * | 2019-10-22 | 2023-04-07 | 华北电力大学 | Balanced control strategy for unbalanced current among multiple MMC current converters |
| CN110912174B (en) * | 2019-12-02 | 2021-03-16 | 中国南方电网有限责任公司超高压输电公司柳州局 | Method and device for stopping multi-terminal direct-current power transmission system under communication fault |
| CN111460610B (en) * | 2020-02-27 | 2022-04-08 | 中国南方电网有限责任公司超高压输电公司广州局 | Converter valve TVM plate heating prediction method, system, device and medium |
| CN113452059A (en) * | 2020-03-25 | 2021-09-28 | 许继电气股份有限公司 | Offshore wind power direct current sending-out system with direct current energy consumption function and control method |
| CN111817332B (en) * | 2020-05-26 | 2021-12-14 | 南方电网科学研究院有限责任公司 | Method and device for power coordination control of direct current transmission system and storage medium |
| CN112103938B (en) * | 2020-10-10 | 2022-06-28 | 北京百度网讯科技有限公司 | Power supply architecture, method and system based on HVDC equipment |
| CN112290576B (en) * | 2020-10-21 | 2022-03-29 | 新疆大学 | Real-time calculation method for eliminating communication delay between extra-high voltage direct current stations |
| CN112653592A (en) * | 2020-11-27 | 2021-04-13 | 中国南方电网有限责任公司 | Method and system for monitoring and evaluating channels between stations in stability control system and storage medium |
| CN112615381B (en) * | 2020-12-12 | 2023-08-15 | 青岛鼎信通讯股份有限公司 | Terminal low voltage of distributed low voltage distribution network administers device |
| CN112290578B (en) * | 2020-12-25 | 2021-03-09 | 中国电力科学研究院有限公司 | Interpolar power compensation control method for high-voltage direct current feed-in weak system |
| CN113300469B (en) * | 2021-06-11 | 2023-03-17 | 山东大学 | Distributed voltage control method of alternating current-direct current system considering control signal loss |
| CN113640709B (en) * | 2021-06-18 | 2023-08-25 | 国网电力科学研究院有限公司 | H-bridge cascade PET test method based on black box test |
| CN113489042B (en) * | 2021-07-01 | 2023-07-18 | 中广核风电有限公司 | Calculation method and device for power sub-module loss of flexible direct current transmission system |
| CN113964821B (en) * | 2021-10-15 | 2023-11-10 | 国网湖北省电力有限公司电力科学研究院 | Small signal model modularized modeling method and device suitable for LCC-HVDC system |
| CN114362232B (en) * | 2021-12-27 | 2023-10-27 | 湖南大学 | Method for defending commutation failure in double-loop same-tower system and control system |
| CN115001044A (en) * | 2022-07-19 | 2022-09-02 | 东南大学溧阳研究院 | Autonomous power sharing control method for current converter |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106849148A (en) * | 2017-03-10 | 2017-06-13 | 南方电网科学研究院有限责任公司 | A kind of Hybrid HVDC system converting plant AC fault traversing control method |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102969733B (en) * | 2012-11-08 | 2014-12-03 | 南京南瑞继保电气有限公司 | Coordination control method of multiterminal flexible direct current power transmission system |
| EP2962377B1 (en) * | 2013-02-27 | 2017-10-18 | Rensselaer Polytechnic Institute | Multi-terminal dc power systems employing autonomous local control methods |
| CN104022522B (en) * | 2014-06-09 | 2016-01-13 | 山东大学 | A kind of coordination control method of multiterminal flexible direct current power transmission system |
| CN105140948B (en) * | 2015-07-06 | 2018-03-30 | 南京南瑞继保电气有限公司 | Flexible direct current power transmission system power coordination control method |
| US9748857B2 (en) * | 2015-08-12 | 2017-08-29 | General Electric Company | Method and system for a gas tube-based current source high voltage direct current transmission system |
| CN105978014B (en) * | 2016-06-08 | 2018-09-28 | 南京南瑞继保电气有限公司 | Parallel inverter direct current transportation interior communication descends failure locking method extremely |
| CN108418237B (en) * | 2018-03-05 | 2021-11-12 | 南京南瑞继保电气有限公司 | Method and device for controlling inter-station communication fault of multi-terminal direct-current power transmission system |
-
2018
- 2018-03-05 CN CN201810178336.5A patent/CN108418237B/en active Active
-
2019
- 2019-03-01 WO PCT/CN2019/076737 patent/WO2019170040A1/en active Application Filing
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106849148A (en) * | 2017-03-10 | 2017-06-13 | 南方电网科学研究院有限责任公司 | A kind of Hybrid HVDC system converting plant AC fault traversing control method |
Non-Patent Citations (1)
| Title |
|---|
| 分层接入方式的特高压直流输电逆变侧最大触发延迟角控制;卢东斌;《中国电机工程学报》;20160405;第36卷(第7期);全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN108418237A (en) | 2018-08-17 |
| WO2019170040A1 (en) | 2019-09-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108418237B (en) | Method and device for controlling inter-station communication fault of multi-terminal direct-current power transmission system | |
| CN108539796B (en) | Fault ride-through and energy dissipation control method for wind power bipolar flexible direct current power grid | |
| CN106849148B (en) | Alternating current fault ride-through control method for rectifying station of hybrid direct current transmission system | |
| CN109066759B (en) | Mixed double-feed-in direct current continuous commutation failure control method considering active balance | |
| CN108683207B (en) | Online switching circuit, switching method and device for hybrid direct current converter valve bank | |
| CN109830978A (en) | A kind of soft lineal system of wind-powered electricity generation having the automatic ride-through capability of failure and control method | |
| CN111600325B (en) | Fault ride-through method and system for hybrid cascaded direct current transmission system | |
| CN107565594B (en) | Multi-DC-to-DC power boost distribution method considering influence of terminal voltage deviation | |
| CN105048488A (en) | Flexible DC network DC short-circuit fault ride through method | |
| CN103997033A (en) | High-voltage direct-current transmission system with direct-current fault ride-through capacity | |
| WO2018098673A1 (en) | Bipolar vsc-hvdc and upfc hybrid topology structure and operating method therefor | |
| WO2021000620A1 (en) | High voltage direct current transmission conversion unit, control method and device, and system main circuit | |
| CN108321829A (en) | Tape jam passes through the Hybrid HVDC system failure processing unit and method of function | |
| CN113067363B (en) | Control method of multi-terminal offshore wind power flexible direct current output system | |
| CN106711943A (en) | Protection device and method for distributed series-coupled power flow controller | |
| CN208723542U (en) | Hybrid HVDC system with trouble handling function | |
| CN113708654A (en) | Flexible direct-current converter valve integrating surplus power dissipation function and control method | |
| CN106849147B (en) | A kind of control method reducing direct current transportation commutation failure probability | |
| CN110233472B (en) | Fault protection method and protection device for voltage source converter | |
| CN105633941A (en) | Commutation failure suppression method based on virtual current limiter | |
| CN112993950A (en) | Flexible direct current converter valve alternating current connecting line single-phase earth fault protection system and method | |
| CN115102217B (en) | Method for determining stable operation domain of MMC at receiving end of LCC-MMC hybrid cascaded direct-current power grid | |
| CN116388255A (en) | Self-adaptive current control method for cascading failure of multi-feed direct-current power transmission system | |
| CN111600323B (en) | Hybrid cascade direct-current power transmission system coordination control method and system | |
| CN114337335B (en) | Hybrid modular multilevel converter, control method and control device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |