CN116565931A - Method and device for inhibiting LCC-VSC mixed direct current commutation failure of receiving end - Google Patents
Method and device for inhibiting LCC-VSC mixed direct current commutation failure of receiving end Download PDFInfo
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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
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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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
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
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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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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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]
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Abstract
The invention discloses a method and a device for inhibiting LCC-VSC mixed direct current commutation failure at a receiving end. The method comprises the following steps: when a short circuit fault or grid voltage drop occurs in the receiving end alternating current grid, calculating the voltage drop of the alternating current conversion bus connected with the LCC according to the detected alternating current conversion bus voltage; under the condition that the voltage drop of the alternating-current converter bus is larger than a preset voltage difference threshold value, switching the reactive power control mode of the VSC to reactive power clamp control; and under the condition that the voltage drop of the alternating-current converter bus is smaller than or equal to the voltage difference threshold value, the reactive power control mode of the VSC is kept unchanged.
Description
Technical Field
The invention relates to the technical field of direct-current transmission of power systems, in particular to a method and a device for inhibiting LCC-VSC mixed direct-current commutation failure of a receiving end.
Background
In recent years, renewable energy sources are greatly developed in China, and particularly remarkable effects are achieved in the field of development and utilization of new energy sources such as wind power, photovoltaics and the like. The renewable energy source in China is concentrated in distribution and far away from the load center area, so that the renewable energy source is sent out by extra-high voltage direct current and is a typical and important power transmission form for large-scale renewable energy source delivery. With the increase of the number of extra-high voltage direct current transmission projects, the problem of direct current commutation failure caused by short circuit fault of the receiving alternating current power grid or power grid voltage drop is more and more serious. There are currently two main types of high voltage direct current transmission, conventional direct current transmission technology (LCC-HVDC) and flexible direct current transmission technology (VSC-HVDC).
The receiving end is an LCC-VSC hybrid direct current system, namely the LCC is used at the transmitting end, and the receiving end uses cascading LCC and VSC. Since the transmission capacity of the LCC receiver is large, a plurality of VSCs are required to be connected in parallel to form a hybrid LCC and VSC to match the dc transmission capacity. The mixed cascading multi-terminal direct current technology combines the advantages of large LCC conveying capacity and no commutation failure of VSC, can provide reactive support for a receiving-terminal alternating current system, and reduces the risk of receiving-terminal direct current commutation failure.
When the receiving end alternating current power grid has short circuit fault or power grid voltage drop, the LCC-HVDC of the receiving end is easy to have commutation failure fault. When the direct current fails to commutate, the current of LCC increases sharply, and the direct current voltage and transmission power drop to zero in a certain time. If the commutation failure fault is not effectively restrained, continuous commutation failure fault can be caused, so that direct current blocking is caused, transmission power is interrupted, and system stability is seriously affected.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method and a device for inhibiting the mixed direct current commutation failure of LCC-VSC at the receiving end.
According to one aspect of the invention, there is provided a method for suppressing a failure of a mixed direct current commutation of an LCC-VSC at a receiving end, comprising:
when a short circuit fault or grid voltage drop occurs in the receiving end alternating current grid, calculating the voltage drop of the alternating current conversion bus connected with the LCC according to the detected alternating current conversion bus voltage;
under the condition that the voltage drop of the alternating-current converter bus is larger than a preset voltage difference threshold value, switching the reactive power control mode of the VSC to reactive power clamp control;
and under the condition that the voltage drop of the alternating-current converter bus is smaller than or equal to the voltage difference threshold value, the reactive power control mode of the VSC is kept unchanged.
Optionally, the formula for calculating the ac-commutated bus voltage drop of the LCC connection from the detected ac-commutated bus voltage is as follows:
ΔU＝(1-U L )
wherein DeltaU is the voltage drop of the alternating current converter bus and is used for representing the severity of faults, U L Is the ac converter bus voltage.
Optionally, the basis formula for switching the reactive power control mode of the VSC to the reactive power clamp control is as follows:
wherein Q is ref Representing the reactive power of the VSC, svsc representing the capacity of the VSC and Pvsc representing the measured active power of the VSC.
Optionally, the method further comprises: the delay time for switching the reactive power control mode of the VSC to the reactive power clamp control is set to 2ms.
Optionally, the method further comprises:
calculating an arc extinction angle of the LCC in a system recovery process after a short circuit fault or a grid voltage drop fault of the receiving end alternating current grid is eliminated;
switching the reactive power control mode of the VSC to the constant ac voltage control mode or the steady state Q under the condition that the arc extinguishing angle of the LCC is equal to or larger than the preset minimum arc extinguishing angle and the delay time of the control mode switching action is not smaller than 2ms ref ＝0。
Alternatively, the arc extinction angle is calculated as follows:
wherein, gamma is the arc extinction angle, k is the converter transformation ratio, I d Is direct current of inversion side, X c Is equivalent commutation reactance, U L Is the voltage of the alternating current conversion busbar at the inversion side, beta is the triggering angle at the inversion side,is the phase shift angle of the voltage waveform, when the ac system is in symmetric failure, +.>Is 0.
According to another aspect of the present invention, there is provided an apparatus for suppressing a failure of a mixed dc commutation of an LCC-VSC at a receiving end, comprising:
the first calculation module is used for calculating the voltage drop of the alternating current conversion bus connected with the LCC according to the detected alternating current conversion bus voltage when the receiving-end alternating current power grid has short circuit fault or power grid voltage drop;
the first switching module is used for switching the reactive power control mode of the VSC to reactive power clamp control under the condition that the voltage drop of the alternating current converting bus is larger than a preset voltage difference threshold value;
and the maintaining module is used for maintaining the reactive power control mode of the VSC unchanged under the condition that the voltage drop of the alternating-current converting bus is smaller than or equal to the voltage difference threshold value.
According to a further aspect of the present invention there is provided a computer readable storage medium storing a computer program for performing the method according to any one of the above aspects of the present invention.
According to still another aspect of the present invention, there is provided an electronic device including: a processor; a memory for storing the processor-executable instructions; the processor is configured to read the executable instructions from the memory and execute the instructions to implement the method according to any of the above aspects of the present invention.
Therefore, the invention provides a method for inhibiting the commutation failure of LCC-VSC mixed direct current at the receiving end, and the proposed commutation failure inhibition strategy can rapidly step reactive power to a maximum value, thereby effectively inhibiting the commutation failure of LCC-HVDC. And the problem of fluctuation of bus voltage and reactive power can be weakened, and the recovery speed of the system fault is effectively improved. For severe voltage drops, the reactive compensation capability of the VSC reaches a limit and the system will still experience a secondary commutation failure. However, the reactive power clamp control strategy can improve the power recovery speed of the system and the recovery characteristic of the system.
Drawings
Exemplary embodiments of the present invention may be more completely understood in consideration of the following drawings:
FIG. 1 is a flow chart of a method for suppressing a mixed DC commutation failure of an LCC-VSC at a receiving end according to an exemplary embodiment of the invention;
FIG. 2 is another flow chart of a method for suppressing a failure of a mixed DC commutation of an LCC-VSC at a receiving end according to an exemplary embodiment of the invention;
fig. 3 is a schematic diagram of an exemplary topology of a hybrid cascading multi-terminal dc power transmission system according to an exemplary embodiment of the present invention;
fig. 4a, 4b, and 4c are schematic diagrams of VSC reactive power, inverter side ac bus voltage, and arc extinction angle, respectively, of scenario 1 provided by an exemplary embodiment of the present invention;
fig. 5a, 5b, and 5c are schematic diagrams of VSC reactive power, inverter side ac bus voltage, and arc extinction angle, respectively, of scenario 2 provided by an exemplary embodiment of the present invention;
FIG. 6 is a graphical representation of CFPI values for original control and improved control of the present scheme provided by an exemplary embodiment of the present invention;
fig. 7 is a schematic structural diagram of an apparatus for suppressing a LCC-VSC hybrid dc commutation failure at a receiving end according to an exemplary embodiment of the present invention;
fig. 8 is a structure of an electronic device provided in an exemplary embodiment of the present invention.
Detailed Description
Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. It should be apparent that the described embodiments are only some embodiments of the present invention and not all embodiments of the present invention, and it should be understood that the present invention is not limited by the example embodiments described herein.
It should be noted that: the relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise.
It will be appreciated by those of skill in the art that the terms "first," "second," etc. in embodiments of the present invention are used merely to distinguish between different steps, devices or modules, etc., and do not represent any particular technical meaning nor necessarily logical order between them.
It should also be understood that in embodiments of the present invention, "plurality" may refer to two or more, and "at least one" may refer to one, two or more.
It should also be appreciated that any component, data, or structure referred to in an embodiment of the invention may be generally understood as one or more without explicit limitation or the contrary in the context.
In addition, the term "and/or" in the present invention is merely an association relationship describing the association object, and indicates that three relationships may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone. In the present invention, the character "/" generally indicates that the front and rear related objects are an or relationship.
It should also be understood that the description of the embodiments of the present invention emphasizes the differences between the embodiments, and that the same or similar features may be referred to each other, and for brevity, will not be described in detail.
Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description.
The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods, and apparatus should be considered part of the specification.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.
Embodiments of the invention are operational with numerous other general purpose or special purpose computing system environments or configurations with electronic devices, such as terminal devices, computer systems, servers, etc. Examples of well known terminal devices, computing systems, environments, and/or configurations that may be suitable for use with the terminal device, computer system, server, or other electronic device include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, hand-held or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network personal computers, small computer systems, mainframe computer systems, and distributed cloud computing technology environments that include any of the foregoing, and the like.
Electronic devices such as terminal devices, computer systems, servers, etc. may be described in the general context of computer system-executable instructions, such as program modules, being executed by a computer system. Generally, program modules may include routines, programs, objects, components, logic, data structures, etc., that perform particular tasks or implement particular abstract data types. The computer system/server may be implemented in a distributed cloud computing environment in which tasks are performed by remote processing devices that are linked through a communications network. In a distributed cloud computing environment, program modules may be located in both local and remote computing system storage media including memory storage devices.
Exemplary method
Fig. 1 is a flow chart of a method for suppressing a mixed dc commutation failure of an LCC-VSC at a receiving end according to an exemplary embodiment of the present invention. The embodiment can be applied to an electronic device, as shown in fig. 1, a method 100 for suppressing a mixed dc commutation failure of an LCC-VSC at a receiving end includes the following steps:
step 101, when a short circuit fault or grid voltage drop occurs in a receiving end alternating current grid, calculating an alternating current conversion bus voltage drop connected with an LCC according to the detected alternating current conversion bus voltage;
102, switching a reactive power control mode of the VSC to reactive power clamp control under the condition that the voltage drop of an alternating current converter bus is larger than a preset voltage difference threshold value;
step 103, under the condition that the voltage drop of the alternating-current converting bus is smaller than or equal to the voltage difference threshold value, the reactive power control mode of the VSC is kept unchanged.
Specifically, referring to fig. 2, the method for suppressing the failure of the receiving end for the LCC-VSC hybrid dc commutation based on the reactive power clamp control provided by the invention fully utilizes the maximum potential reactive power of all the parallel VSCs. The method comprises the following steps:
step 1: detecting an ac converter bus voltage U L ；
Step 2: ac commutation bus voltage drop Δu= (1-U) for LCC connection L ) ΔU is used to characterize the severity of the fault;
step 3: if DeltaU > epsilon, where epsilon is a measure of the voltage difference, typically 0.1p.u., a reactive power control mode of the VSC is switched to the proposed reactive power clamp control, a severe fault is indicated. According to the following
The reactive power control mode of the VSC is switched to the reactive power clamping control mode, so that the maximum reactive power output by the VSC can be realized. Wherein Q is ref Representing the reactive power of the VSC, svsc representing the capacity of the VSC and Pvsc representing the measured active power of the VSC. The delay time of the control mode switching action is set to 2ms to simulate the failure detection delay.
Step 4: if DeltaU is less than or equal to epsilon, the reactive power control mode of the VSC is kept unchanged;
step 5: in the system recovery process after fault elimination, the arc extinction angle gamma of the LCC is used as a judgment basis for stable operation.
Gamma can be expressed as:
wherein k is the converter transformation ratio, I d Is direct current of inversion side, X c Is equivalent commutation reactance, U L Is the inversion side commutation bus voltage, beta is the inversion side trigger angle,is the phase shift angle of the voltage waveform, when the ac system is in symmetric failure, +.>Is 0.
If gamma is not less than gamma re ，γ re At the minimum arc extinction angle, the reactive power control mode of the VSC is switched to constant ac voltage control or qref=0.
In addition, a typical LCC-VSC hybrid direct current model is established in PSCAD. The model structure is shown in fig. 3. In the mixed cascading multi-terminal direct current transmission system, an LCC topological structure is used for both the positive electrode and the negative electrode of a transmitting terminal, a topological structure consisting of cascading LCC and VSC is used for both the positive electrode and the negative electrode of a receiving terminal, LCC topology is used for both the positive electrode and the negative electrode of the receiving terminal, and three VSCs which are connected in parallel are used for both the low-voltage group. Taking a typical +/-800 kV power transmission system as an example, an +/-800 kV LCC converter is used at a transmitting end, an +/-400 kV LCC converter is used at a receiving end in a high-voltage group, and an +/-400 kV parallel VSC converter is used at a low-voltage group. The transmitting end uses an LCC converter with the transmission capacity of 8GW of plus or minus 800kV, the receiving end uses an LCC converter with the interelectrode voltage of plus or minus 400kV at the high end, and uses three parallel VSC converters with the interelectrode voltage of plus or minus 400kV at the low end. The high-end and low-end capacities are both 4GW. Furthermore, the capacity of a single VSC is 1500MVA, the rated power is 833MVA, and the reactive power is about 1247MVar. The main structure and control strategy of LCC are the same as CIGRE standard test model. The VSC1 station adopts constant direct voltage control and constant reactive power control, and the VSC2 and VSC3 stations adopt constant active power control and constant reactive power control. The main parameters of the system are shown in table 1.
TABLE 1
By way of comparison, the following two control strategies will simulate and verify under different ac system faults.
Scheme one: original control strategies in CIGRE standard test models.
Scheme II: the reactive power clamp control improvement strategy presented herein is employed.
1. System transient characteristic comparison
In this section, two grounding inductance values of l=0.4h and 0.2h are selected from large to small to simulate different ac system conditions. The effectiveness of the proposed control strategy is analyzed by comparing the change of each charge of the LCC-VSC system under different fault conditions using scheme one and scheme two, respectively.
Scene 1: three-phase short circuit fault occurs on the alternating current bus connected with the LCC, and the grounding inductance is set to be 0.4H. Fault start time t=0.8 s, fault duration 0.1s. The simulation results are shown in fig. 4a, 4b and 4 c. When the scheme is used after the fault, the VSC basically does not generate reactive power, the arc extinguishing angle is reduced to 0, and the commutation failure of the LCC at the receiving end is caused. When the scheme II is used, when a fault is detected, the VSC1 station can switch to a constant alternating voltage control mode, the reactive power output by the VSC is larger, the voltage drop is smaller, the arc extinguishing angle does not suddenly fluctuate, the LCC of the receiving end does not have commutation failure fault, and the reactive power clamping control scheme can ensure the stability of the alternating voltage of the receiving end and reduce the risk of commutation failure.
Scene 2: the receiving end alternating current bus is provided with a three-phase grounding short circuit fault, the grounding inductance is set to be 0.2H, and the fault point is close to the alternating current bus, so that the fault is serious. Fault start time t=0.8 s, fault duration 0.1s. The simulation results are shown in fig. 5a, 5b and 5 c. Under the original control strategy, the LCC arc extinction angle gamma is reduced to 0 twice, which means that two continuous commutation faults occur. With the proposed reactive power clamp control strategy, the three VSC stations change the reactive power to qref=0.98 p.u.. The figure shows that although the first commutation failure is unavoidable, no second commutation failure occurs. Meanwhile, after the fault is removed, the direct current relatively quickly resumes normal operation.
2. Anti-interference performance comparison in case of commutation failure
The probability of commutation failure in the system is measured using a Commutation Failure Immunity Index (CFII) and a Commutation Failure Probability Index (CFPI) in the present invention, and the calculation formula is as follows.
U in ac And rated line voltage of the inversion side converter bus. L (L) min Is the critical fault inductance. P (P) dc Is the rated direct current power of the high-voltage direct current transmission system.
Wherein N is CF Is the commutation failure times, N A Is the analog total number for each cycle. The higher the value of CFII, the lower the value of CFPI, the more resistant the inverter LCC is to commutation failure.
The Multirun model simulation with PSCAD/EMTDC software set 100 failure points at equal intervals over a period of 0.02 s. The critical fault inductance is the minimum inductance that will not fail at all points of failure during one cycle. CFPI is the percentage of failure points of the 100 failure points at which commutation failure occurs.
The probability of inverter commutation failure when a three-phase or single-phase fault occurs in the ac bus is shown in table 2. As can be seen from the data in table 2, the CFII value for scheme two with the proposed reactive power clamp control is higher than the CFII value for scheme one, which verifies the correctness and validity of the proposed inhibit commutation failure strategy.
TABLE 2
As can be seen from the graph of CFPI values in fig. 6, when the voltage of the commutation bus drops to about 5%, the original control strategy starts to generate a commutation failure fault, and when the voltage of the commutation bus drops to 10%, the commutation failure fault is necessarily generated. By adopting the proposed commutation failure suppression strategy based on reactive power clamp control, commutation failure starts to occur when the voltage of the alternating current bus is reduced to about 15%, and commutation failure inevitably occurs when the voltage of the alternating current commutation bus is reduced to 35%. The comparison result shows that the improved control strategy can effectively improve the capacity of inhibiting commutation failure of the receiving LCC-HVDC system.
Thus, the commutation failure suppression strategy presented herein can quickly step reactive power to a maximum value, thereby effectively suppressing commutation failure of LCC-HVDC. 2. The control strategy provided can weaken the fluctuation problem of bus voltage and reactive power, and effectively improve the recovery speed of system faults. 3. For severe voltage drops, the reactive compensation capability of the VSC reaches a limit and the system will still experience a secondary commutation failure. However, the reactive power clamp control strategy can improve the power recovery speed of the system and the recovery characteristic of the system.
Exemplary apparatus
Fig. 7 is a schematic structural diagram of an apparatus for suppressing a LCC-VSC hybrid dc commutation failure at a receiving end according to an exemplary embodiment of the present invention. As shown in fig. 7, the apparatus 700 includes:
the first calculation module 710 is configured to calculate an ac converter bus voltage drop of the LCC connection according to the detected ac converter bus voltage when a short circuit fault or a grid voltage drop occurs in the receiving ac grid;
a first switching module 720, configured to switch a reactive power control mode of the VSC to reactive power clamping control when the ac commutation bus voltage drop is greater than a preset voltage differential threshold;
the maintaining module 730 is configured to maintain the reactive power control mode of the VSC unchanged when the ac commutation bus voltage drop is equal to or less than the voltage differential threshold.
Optionally, the formula for calculating the ac-commutated bus voltage drop of the LCC connection from the detected ac-commutated bus voltage is as follows:
ΔU＝(1-U L )
wherein DeltaU is alternating current converterBus voltage drop for characterizing severity of fault, U L Is the ac converter bus voltage.
Optionally, the basis formula for switching the reactive power control mode of the VSC to the reactive power clamp control is as follows:
wherein Q is ref Representing the reactive power of the VSC, svsc representing the capacity of the VSC and Pvsc representing the measured active power of the VSC.
Optionally, the apparatus 700 further comprises: and the setting module is used for setting the delay time for switching the reactive power control mode of the VSC to the reactive power clamp control to be 2ms.
Optionally, the apparatus 700 further comprises:
the second calculation module is used for calculating the arc extinction angle of the LCC in the system recovery process after the short circuit fault or the grid voltage drop fault of the receiving end alternating current grid is eliminated;
a second switching module for switching the reactive power control mode of the VSC to the constant ac voltage control mode or the steady state Q when the arc extinction angle of the LCC is equal to or greater than a preset minimum arc extinction angle and the delay time of the control mode switching action is not less than 2ms ref ＝0。
Alternatively, the arc extinction angle is calculated as follows:
wherein, gamma is the arc extinction angle, k is the converter transformation ratio, I d Is direct current of inversion side, X c Is equivalent commutation reactance, U L Is the voltage of the alternating current conversion busbar at the inversion side, beta is the triggering angle at the inversion side,is the phase shift angle of the voltage waveform, when the AC system has symmetrical faultWhen (I)>Is 0.
Exemplary electronic device
Fig. 8 is a structure of an electronic device provided in an exemplary embodiment of the present invention. As shown in fig. 8, the electronic device 80 includes one or more processors 81 and memory 82.
The processor 81 may be a Central Processing Unit (CPU) or other form of processing unit having data processing and/or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.
Memory 82 may include one or more computer program products that may include various forms of computer-readable storage media, such as volatile memory and/or non-volatile memory. The volatile memory may include, for example, random Access Memory (RAM) and/or cache memory (cache), and the like. The non-volatile memory may include, for example, read Only Memory (ROM), hard disk, flash memory, and the like. One or more computer program instructions may be stored on the computer readable storage medium that can be executed by the processor 81 to implement the methods of the software programs of the various embodiments of the present invention described above and/or other desired functions. In one example, the electronic device may further include: an input device 83 and an output device 84, which are interconnected by a bus system and/or other forms of connection mechanisms (not shown).
In addition, the input device 83 may also include, for example, a keyboard, a mouse, and the like.
The output device 84 can output various information to the outside. The output means 84 may include, for example, a display, speakers, a printer, and a communication network and remote output devices connected thereto, etc.
Of course, only some of the components of the electronic device relevant to the present invention are shown in fig. 8 for simplicity, components such as buses, input/output interfaces, etc. being omitted. In addition, the electronic device may include any other suitable components depending on the particular application.
Exemplary computer program product and computer readable storage Medium
In addition to the methods and apparatus described above, embodiments of the invention may also be a computer program product comprising computer program instructions which, when executed by a processor, cause the processor to perform steps in a method according to various embodiments of the invention described in the "exemplary methods" section of this specification.
The computer program product may write program code for performing operations of embodiments of the present invention in any combination of one or more programming languages, including an object oriented programming language such as Java, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device, partly on a remote computing device, or entirely on the remote computing device or server.
Furthermore, embodiments of the invention may also be a computer-readable storage medium, having stored thereon computer program instructions, which when executed by a processor, cause the processor to perform steps in a method according to various embodiments of the invention described in the "exemplary method" section of the description above.
The computer readable storage medium may employ any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium can include, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the readable storage medium would include the following: an electrical connection having one or more wires, a portable disk, a hard disk, random Access Memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
The basic principles of the present invention have been described above in connection with specific embodiments, however, it should be noted that the advantages, benefits, effects, etc. mentioned in the present invention are merely examples and not intended to be limiting, and these advantages, benefits, effects, etc. are not to be considered as essential to the various embodiments of the present invention. Furthermore, the specific details disclosed herein are for purposes of illustration and understanding only, and are not intended to be limiting, as the invention is not necessarily limited to practice with the above described specific details.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different manner from other embodiments, so that the same or similar parts between the embodiments are mutually referred to. For system embodiments, the description is relatively simple as it essentially corresponds to method embodiments, and reference should be made to the description of method embodiments for relevant points.
The block diagrams of the devices, systems, apparatuses, systems according to the present invention are merely illustrative examples and are not intended to require or imply that the connections, arrangements, configurations must be made in the manner shown in the block diagrams. As will be appreciated by one of skill in the art, the devices, systems, apparatuses, systems may be connected, arranged, configured in any manner. Words such as "including," "comprising," "having," and the like are words of openness and mean "including but not limited to," and are used interchangeably therewith. The terms "or" and "as used herein refer to and are used interchangeably with the term" and/or "unless the context clearly indicates otherwise. The term "such as" as used herein refers to, and is used interchangeably with, the phrase "such as, but not limited to.
The method and system of the present invention may be implemented in a number of ways. For example, the methods and systems of the present invention may be implemented by software, hardware, firmware, or any combination of software, hardware, firmware. The above-described sequence of steps for the method is for illustration only, and the steps of the method of the present invention are not limited to the sequence specifically described above unless specifically stated otherwise. Furthermore, in some embodiments, the present invention may also be embodied as programs recorded in a recording medium, the programs including machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers a recording medium storing a program for executing the method according to the present invention.
It is also noted that in the systems, devices and methods of the present invention, components or steps may be disassembled and/or assembled. Such decomposition and/or recombination should be considered as equivalent aspects of the present invention. The previous description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The foregoing description has been presented for purposes of illustration and description. Furthermore, this description is not intended to limit embodiments of the invention to the form disclosed herein. Although a number of example aspects and embodiments have been discussed above, a person of ordinary skill in the art will recognize certain variations, modifications, alterations, additions, and subcombinations thereof.
Claims (9)
1. A method for suppressing a failure of a mixed direct current commutation with a LCC-VSC at a receiving end, comprising:
when a short circuit fault or grid voltage drop occurs in the receiving end alternating current grid, calculating the voltage drop of the alternating current conversion bus connected with the LCC according to the detected alternating current conversion bus voltage;
under the condition that the voltage drop of the alternating-current converter bus is larger than a preset voltage difference threshold value, switching a reactive power control mode of the VSC to reactive power clamp control;
and under the condition that the voltage drop of the alternating-current converting bus is smaller than or equal to the voltage difference threshold value, the reactive power control mode of the VSC is kept unchanged.
2. The method of claim 1, wherein the formula for calculating the ac converter bus voltage drop for the LCC connection based on the detected ac converter bus voltage is as follows:
ΔU＝(1-U L )
wherein DeltaU is the voltage drop of the alternating current converter bus and is used for representing the severity of faults, U L Is the ac converter bus voltage.
3. The method according to claim 1, characterized in that the basis formula for switching the reactive power control mode of the VSC to the reactive power clamp control is as follows:
wherein Q is ref Representing the reactive power of the VSC, svsc representing the capacity of the VSC and Pvsc representing the measured active power of the VSC.
4. The method as recited in claim 1, further comprising: the delay time for switching the reactive power control mode of the VSC to the reactive power clamp control is set to 2ms.
5. The method as recited in claim 1, further comprising:
calculating an arc extinguishing angle of the LCC in a system recovery process after the short circuit fault or the grid voltage drop fault of the receiving end alternating current grid is eliminated;
switching the reactive power control mode of the VSC to a constant ac voltage control mode or a steady state Q in the case where the arc extinction angle of the LCC is equal to or greater than a preset minimum arc extinction angle and the delay time of the control mode switching action is not less than 2ms ref ＝0。
6. The method of claim 5, wherein the arc extinction angle is calculated as:
wherein, gamma is the arc extinction angle, k is the converter transformation ratio, I d Is direct current of inversion side, X c Is equivalent commutation reactance, U L Is the voltage of the alternating current conversion busbar at the inversion side, beta is the triggering angle at the inversion side,is the phase shift angle of the voltage waveform, when the ac system is in symmetric failure, +.>Is 0.
7. A device for suppressing a failure of a mixed dc commutation with LCC-VSC at a receiving end, comprising:
the first calculation module is used for calculating the voltage drop of the alternating current conversion bus connected with the LCC according to the detected alternating current conversion bus voltage when the receiving-end alternating current power grid has short circuit fault or power grid voltage drop;
the first switching module is used for switching the reactive power control mode of the VSC to reactive power clamp control under the condition that the voltage drop of the alternating current converting bus is larger than a preset voltage difference threshold value;
and the maintaining module is used for maintaining the reactive power control mode of the VSC unchanged under the condition that the voltage drop of the alternating current converting bus is smaller than or equal to the voltage difference threshold value.
8. A computer readable storage medium, characterized in that the storage medium stores a computer program for executing the method of any of the preceding claims 1-6.
9. An electronic device, the electronic device comprising:
a processor;
a memory for storing the processor-executable instructions;
the processor is configured to read the executable instructions from the memory and execute the instructions to implement the method of any of the preceding claims 1-6.
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| CN117955148A (en) * | 2024-03-26 | 2024-04-30 | 浙江大学 | Commutation failure fault collaborative recovery method for hybrid multi-feed direct current transmission system |
| CN117955148B (en) * | 2024-03-26 | 2024-05-28 | 浙江大学 | Commutation failure fault collaborative recovery method for hybrid multi-feed direct current transmission system |
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