CN117039820A - Surplus power overvoltage suppression method and system for high-capacity flexible direct current converter valve - Google Patents
Surplus power overvoltage suppression method and system for high-capacity flexible direct current converter valve Download PDFInfo
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- CN117039820A CN117039820A CN202311148952.3A CN202311148952A CN117039820A CN 117039820 A CN117039820 A CN 117039820A CN 202311148952 A CN202311148952 A CN 202311148952A CN 117039820 A CN117039820 A CN 117039820A
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Classifications
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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
- H02H7/268—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 for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/20—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage
- H02H3/202—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
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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 relates to a method and a system for inhibiting surplus power overvoltage of a high-capacity flexible direct current converter valve, wherein the method comprises the following steps: all types of faults of the alternating current system are subjected to global simulation scanning, and three grades are classified according to the adopted measures according to simulation results: minor, moderate, and severe faults; for slight faults, hardware or control additional strategies are not needed, and fault ride-through is realized by means of the overvoltage tolerance capability of the equipment; for medium faults, the transmitting end rapidly reduces the transmitted direct current power after identifying the faults, so as to realize fault ride-through; for serious faults, the receiving end needs to quickly enter a power quick cut-off mode after the faults are identified, and the transmission of surplus power on the direct current side is quickly blocked. The invention can effectively reduce the overvoltage level of the converter valve when the receiving end alternating current system fails, and avoid blocking caused by failure of fault ride-through; can be widely applied to the field of direct current transmission.
Description
Technical Field
The invention relates to the technical field of direct-current transmission, in particular to a method and a system for inhibiting surplus power overvoltage of a high-capacity flexible direct-current converter valve for long-distance overhead line transmission.
Background
The flexible direct current adopts a fully-controlled IGBT device, is a voltage source type converter, gets rid of dependence on an alternating current power grid in principle, has important technical advantages of no commutation failure, black start capability, active and reactive independent decoupling control, flexible operation mode, capability of realizing large-scale tide regulation and control and the like, is widely applied to application scenes such as asynchronous power grid interconnection, new energy transmission and the like, and is an important technology for realizing a 'double-carbon' target and constructing a novel power system in the future.
The flexible direct current device has weaker transient voltage tolerance, taking an IGBT device with the rated voltage of 4.5kV as an example, the maximum current which can be repeatedly turned off during unlocking operation is only 2 times of rated current, and the maximum operation voltage under the current is 3.4kV. Therefore, when the AC/DC system fails, the overvoltage of the converter valve reaches the protection fixed value to be blocked, so that failure of fault ride-through is caused easily. Particularly for a long-distance high-capacity flexible direct current system, when an alternating current system fault occurs at a receiving end, on one hand, the sending end cannot reduce the sent direct current power in time due to the long distance, so that surplus power continuously flows into the receiving end converter valve; on the other hand, due to the long line, the equivalent inductance is large, and the energy stored on the line is large, and the energy flows into the receiving-end converter valve. Therefore, for a long-distance large-capacity flexible direct current system, the development speed and the amplitude of direct current overvoltage caused by the fault of a receiving end alternating current system are faster, particularly for a flexible direct current system with the speed of more than 2000 km, if no measures are taken, the overvoltage of a converter valve sub-module under the fault of the alternating current system can even reach more than 4kV, and the maximum overvoltage capacity of a converter valve under the unlocking running state of the converter valve is far more than 3.4kV, so that the overvoltage protection action of the converter valve is caused, the converter valve is locked and tripped, and the fault ride through fails.
To solve this problem, there are two general solutions: one is to increase the number of modules or increase the capacitance of the modules, thereby improving the capacity of the converter valve itself to absorb surplus power and reducing the overvoltage of a single module; the other is to configure the energy consumption device to consume surplus power. Both of the foregoing methods, however, require a substantial increase in equipment costs and engineering investments. There is a need to study low cost excess power overvoltage suppression methods and systems.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a method and a system for inhibiting excess power overvoltage of a high-capacity flexible direct current converter valve, which can effectively reduce the overvoltage level of the converter valve when a receiving end alternating current system fails and avoid blocking caused by failure of fault ride-through.
In order to achieve the above purpose, the present invention adopts the following technical scheme: a method for inhibiting surplus power overvoltage of a high-capacity flexible direct current converter valve comprises the following steps: all types of faults of the alternating current system are subjected to global simulation scanning, and three grades are classified according to the adopted measures according to simulation results: minor, moderate, and severe faults; for slight faults, hardware or control additional strategies are not needed, and fault ride-through is realized by means of the overvoltage tolerance capability of the equipment; for medium faults, the transmitting end rapidly reduces the transmitted direct current power after identifying the faults, so as to realize fault ride-through; for serious faults, the receiving end needs to quickly enter a power quick cut-off mode after the faults are identified, and the transmission of surplus power on the direct current side is quickly blocked.
Further, according to the simulation result, the steps are classified into three classes according to the measures taken, including:
taking the positive sequence voltage drop amplitude as a criterion, and taking no measures according to simulation results, wherein the fault which can be directly traversed is a slight fault, and the corresponding boundary voltage drop is Uacset1; the corresponding fault that the power supply end can pass through is a medium fault, and the corresponding boundary voltage drops to Uacset2; faults that must be in "power fast phase mode" are critical faults.
Further, the overpressure tolerance capability of the device itself, including: short-time overload capacity and the characteristic that overvoltage and overcurrent peaks are asynchronous when voltage of the flexible direct current module fluctuates;
short-time overload capacity, namely rapidly increasing the current of the converter valve to the maximum overload level when the alternating current is low in voltage, and increasing the dissipation of surplus power;
the characteristics that overvoltage and overcurrent peaks are asynchronous when the voltage of the flexible direct current module fluctuates are utilized, and the surplus power absorbed by an energy storage element of the converter valve is increased by utilizing the higher overvoltage capacity of the converter valve when the current is small.
Further, for a slight fault, at least it is ensured that under a single-phase ground fault, no measures are taken, and only the capability of the device is utilized to limit the overvoltage of the converter valve within a safety range, and if the overvoltage cannot be met, the number of sub-modules or the module capacitance should be increased until the requirement is met.
Further, the transmitting end rapidly reduces the transmitted direct current power, including:
the method comprises the steps that a sending end automatically monitors the rising of port direct current voltage, and when the port direct current voltage rises to a boundary voltage drop value Udcset1 corresponding to a slight fault, the reference value of active current in a converter control system is quickly reduced to a preset value idset1;
after the medium fault is identified by the receiving end, the medium fault is transmitted to the transmitting end converter station through inter-station communication, and the transmitting end converter station rapidly reduces the active current reference value to a preset value idset1 after receiving the rapid power reduction instruction transmitted by the receiving end.
Further, the preset value idset1 is: idset1/idN is less than Uacset2/UacN, uacset2 is a boundary voltage drop value corresponding to a medium fault, idN is a transmitting end active current rated value, and UacN is a receiving end alternating current bus voltage rated value.
Further, "power fast cut-off mode", includes:
for a flexible direct current system adopting a half-bridge type converter and a direct current breaker, the direct current breaker is quickly tripped to block the transmission of direct current power, and at the moment, surplus power is dissipated in a sending-end flexible direct current converter valve and an energy dissipation lightning arrester of the direct current breaker;
for a flexible direct current system adopting a full-bridge-half-bridge hybrid direct current breaker, a receiving end rapidly controls the port direct current voltage to be 0 so as to block the direct current side power from accumulating in a converter valve, at the moment, the direct current is increased, and surplus power is converted into electromagnetic energy stored in an inductor on a direct current line.
A high capacity flexible dc converter valve surplus power overvoltage suppression system comprising: the fault dividing module carries out global simulation scanning on all types of faults of the alternating current system, and divides the faults into three grades according to the simulation results and the measures taken: minor, moderate, and severe faults; the slight fault processing module is used for realizing fault ride-through by means of the overvoltage tolerance capability of the equipment without adopting hardware or controlling an additional strategy for slight faults; the medium fault processing module is used for rapidly reducing the transmitted direct current power by the transmitting end after identifying the medium fault so as to realize fault ride-through; and for the serious fault, the receiving end rapidly enters a power rapid cut-off mode after the fault is identified, so that the transmission of surplus power on the direct current side is rapidly blocked.
A computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by a computing device, cause the computing device to perform any of the methods described above.
A computing apparatus, comprising: one or more processors, memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs comprising instructions for performing any of the methods described above.
Due to the adoption of the technical scheme, the invention has the following advantages:
1. the invention systematically divides the fault types of surplus power according to different influences on the system for the first time, and proposes fault processing strategies of different levels, thereby realizing the maximum guarantee of the power transmission capacity during faults on the premise of guaranteeing the surplus power fault ride-through capacity.
2. The invention realizes the hard cut-off of direct current power in a few milliseconds through the proposed power quick cut-off mode, and thoroughly solves the problem of overvoltage of the converter valve under the most severe faults such as alternating current three-phase metal short circuit and the like.
3. The technical scheme of the invention solves the problem of serious overvoltage caused by the increase of the transmission distance on the premise of not depending on any hardware equipment investment, and effectively avoids the improvement of the manufacturing cost of the converter valve and the engineering investment.
Drawings
FIG. 1 is a flowchart of a method for suppressing excess power overvoltage of a high-capacity flexible DC converter valve in an embodiment of the invention;
FIG. 2 is a schematic diagram of a flexible DC system with a large capacity and a long distance of + -800 kV/8GW in an embodiment of the invention;
FIG. 3 is a detailed flow chart of a method for suppressing excess power overvoltage of a high-capacity flexible DC converter valve in an embodiment of the invention;
fig. 4 is a dc power policy control block diagram of a fast reduced transmission at a transmitting end according to an embodiment of the present invention;
fig. 5 is a flowchart of a power fast cut-off mode implementation in an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which are obtained by a person skilled in the art based on the described embodiments of the invention, fall within the scope of protection of the invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
The invention relates to a method and a system for suppressing surplus power overvoltage of a high-capacity flexible direct current converter valve transmitted by a long-distance overhead line, which comprise the following steps: dividing all types of faults of an alternating current system into three levels according to the measures taken, and respectively adopting different inhibition methods, namely a three-section surplus power inhibition method; for slight faults, hardware or control additional strategies are not needed, and fault ride-through is realized by means of the overvoltage tolerance capability of the equipment; for medium faults, the transmitting end rapidly reduces the transmitted direct current power to realize fault ride-through after identifying the faults; for serious faults, the fault ride through is realized by entering a power quick cut-off mode, and the power quick cut-off mode is as follows: for a flexible direct current system adopting a half-bridge type converter and a direct current breaker, the direct current breaker is quickly tripped to block the transmission of direct current power, and for a flexible direct current system adopting a full-bridge and half-bridge hybrid type direct current breaker, the port direct current voltage is quickly controlled to be 0. The invention can effectively prevent the overvoltage level of the converter valve from exceeding the standard to lock the converter valve when surplus power is caused by the alternating current fault of the high-capacity flexible direct current system transmitted by the long-distance overhead line, improve the reliability and reduce the manufacturing cost of equipment. The invention can be applied to the field of direct current transmission.
In one embodiment of the invention, a method for suppressing excess power overvoltage of a high-capacity flexible direct current converter valve is provided. In this embodiment, as shown in fig. 1, the method includes the following steps:
1) All types of faults of the alternating current system are subjected to global simulation scanning, and three grades are classified according to the adopted measures according to simulation results: minor, moderate, and severe faults;
2) For slight faults, hardware or control additional strategies are not needed, and fault ride-through is realized by means of the overvoltage tolerance capability of the equipment;
3) For medium faults, the transmitting end rapidly reduces the transmitted direct current power after identifying the faults, so as to realize fault ride-through;
4) For serious faults, the receiving end needs to quickly enter a power quick cut-off mode after the faults are identified, and the transmission of surplus power on the direct current side is quickly blocked.
In the step 1), all types of faults of the alternating current system include: single-phase earth transient faults, single-phase earth permanent faults, interphase short-circuit faults, two-phase earth faults, and three-phase short-circuit faults.
The simulation result is divided into three grades according to the adopted measures, and different suppression methods are adopted respectively, namely a three-section surplus power suppression method. The method comprises the following steps:
taking the positive sequence voltage drop amplitude as a criterion, and taking no measures according to simulation results, wherein the fault which can be directly traversed is a slight fault, and the corresponding boundary voltage drop is Uacset1; the corresponding fault that the power supply end can pass through is a medium fault, and the corresponding boundary voltage drops to Uacset2; faults that must be in "power fast phase mode" are critical faults.
When Uac > Uacset1, a slight fault; when Uacset1 > Uac > Uacset2, a moderate fault is present; when Uac < Uacset2, a severe fault is present. Wherein Uac is the amplitude of the AC bus.
In this embodiment, a light fault is defined as a level one, a medium fault is defined as a level two, and a severe fault is defined as a level three.
In step 2) above, the overpressure tolerance capability of the device itself includes the following two capabilities: short-time overload capacity and the characteristic that overvoltage and overcurrent peaks are asynchronous when voltage of the flexible direct current module fluctuates.
In this embodiment, the short-time overload capability is specifically: and when the alternating current is low in voltage, the current of the converter valve is quickly increased to the maximum overload level, the dissipation of surplus power is increased, the junction temperature calculation of the converter valve is carried out by combining the fault duration time in the short-time overload capacity, and the maximum bridge arm current which can run at the limited junction temperature is determined.
The characteristics of asynchronous overvoltage and overcurrent peak values when the voltage of the flexible direct current module fluctuates are utilized, and the characteristics are as follows: the capacity of the maximum operation voltage of the module of the flexible direct current under small current is determined by combining a module double-pulse test according to the principle that the operation voltage is not more than the rated voltage of the module after the peak voltage is overlapped and cut off by utilizing the higher overvoltage capacity of the converter valve with small current and increasing surplus power absorbed by an energy storage element of the converter valve.
In the step 2), for the slight fault, at least it is ensured that under the single-phase ground fault, no measures are taken, and only the capability of the equipment is utilized to limit the overvoltage of the converter valve within a safety range, if the overvoltage cannot be met, the number of sub-modules or the module capacitance should be increased until the requirement is met.
In the step 3), the transmitting end rapidly reduces the transmitted direct current power, and the method comprises the following steps:
3.1 Automatically monitoring the rising of the port direct current voltage by the transmitting end, and rapidly reducing the reference value idref of the active current in the converter control system to a preset value idset1 when the port direct current voltage rises to a boundary voltage drop value Udcset1 corresponding to a slight fault;
3.2 After the medium fault is identified by the receiving end, the medium fault is transmitted to the transmitting end converter station through inter-station communication, and the transmitting end converter station rapidly reduces the active current reference value idref to a preset value idset1 after receiving the rapid power reduction command transmitted by the receiving end.
In this embodiment, the preset value idset1 is: idset1/idN is less than Uacset2/UacN, uacset2 is a boundary voltage drop value corresponding to a medium fault, idN is a transmitting end active current rated value, and UacN is a receiving end alternating current bus voltage rated value, so that the amplitude of the rapid power reduction is ensured to be large enough.
In the step 4), the "power fast cut-off mode" specifically includes:
for a flexible direct current system adopting a half-bridge type converter and a direct current breaker, the direct current breaker is quickly tripped to block the transmission of direct current power, and at the moment, surplus power is dissipated in a sending-end flexible direct current converter valve and an energy dissipation lightning arrester of the direct current breaker;
for a flexible direct current system adopting a full-bridge-half-bridge hybrid direct current breaker, a receiving end rapidly controls the port direct current voltage to be 0 so as to block the direct current side power from accumulating in a converter valve, at the moment, the direct current is increased, and surplus power is converted into electromagnetic energy stored in an inductor on a direct current line.
In the embodiment, a ±800kV/8GW high-capacity flexible dc system as shown in fig. 2 is adopted, and fig. 3 is a detailed flowchart of a method for suppressing excess power overvoltage of a high-capacity flexible dc converter valve for long-distance overhead line transmission, where in the embodiment, the method includes the following steps:
1) Establishing an electromagnetic transient simulation model of a high-capacity flexible direct current system of +/-800 kV/8 GW;
2) And carrying out global simulation scanning on single-phase grounding transient faults, single-phase grounding permanent faults, interphase short-circuit faults, two-phase grounding faults, three-phase short-circuit faults and different voltage drop levels based on a simulation model, wherein in the calculation process, the low-voltage current limiting of a converter valve is required to be adjusted to the maximum overload level of the short-time converter valve, and an overvoltage protection fixed value is adjusted to a fixed value considering the characteristic of asynchronous overvoltage and overcurrent peak values when the voltage of the flexible direct current module fluctuates. After the simulation result is obtained, all faults which can be directly traversed are slight faults. The alternating current bus voltage amplitude with the largest voltage drop degree under the fault is Uac1, a certain safety margin Umar is taken, and a slight fault threshold Uacset1 = Uac1+ Umar is set. If the direct crossing cannot be realized under the single-phase grounding fault, the number of sub-modules and the capacitance are increased, and the steps are repeated.
3) For faults which cannot be directly traversed, a strategy for increasing the sending end to quickly reduce the power is added, and two methods are included: firstly, a transmitting end automatically monitors the rising of the port direct current voltage, and when the port direct current voltage rises to a certain fixed value Udcset1, the reference value idref of active current in the converter control system is quickly reduced to the fixed value idset1; and secondly, after the medium fault is identified by the receiving end, the medium fault is transmitted to the transmitting end converter station through inter-station communication, and after the transmitting end converter station receives the rapid power reduction instruction transmitted by the receiving end, the active current reference value idref is rapidly reduced to a fixed value idset1. Either action of the two criteria directly reduces the power. The strategy for fast power reduction at the transmit end is shown in fig. 4. After the simulation result is obtained, all faults which can be traversed are defined as medium faults, the alternating current bus voltage amplitude with the largest voltage drop degree under the faults is Uac2, a certain safety margin Umar is taken, and the medium fault margin Uacset2 = Uac2+ Umar is set.
4) For the faults which cannot be traversed in step 3), the faults are directly defined as serious faults, namely faults with alternating current bus amplitude Uac < Uacset 2. For such faults, a strategy of "power fast cut-off mode" is adopted, which is as follows, according to the adopted topology structure: for a flexible direct current system adopting a half-bridge type converter and a direct current breaker, the direct current breaker is quickly tripped to block the transmission of direct current power, and at the moment, surplus power is dissipated in a sending-end flexible direct current converter valve and an energy dissipation lightning arrester of the direct current breaker; for a flexible direct current system adopting a full-bridge-half-bridge hybrid direct current breaker, the port direct current voltage is rapidly controlled to be 0, so that the accumulation of direct current side power in a converter valve is blocked, at the moment, the direct current is increased, and surplus power is converted into electromagnetic energy stored in an inductor on a direct current line, as shown in fig. 5.
In summary, when the invention is used, all types of faults of the alternating current system are subjected to global simulation scanning, and three grades are classified according to measures taken according to simulation results: slight, medium and severe faults, and respectively adopting different suppression methods, namely a three-section surplus power suppression method. For slight faults, hardware or control additional strategies are not needed, and fault ride-through can be realized by means of the overvoltage tolerance capability of the equipment; for medium faults, the transmitting end can quickly reduce the transmitted direct current power after identifying the faults, so that fault ride-through can be realized; for serious faults, the receiving end needs to quickly enter a power quick cut-off mode after the faults are identified, so that the transmission of surplus power on the direct current side is quickly blocked.
In one embodiment of the present invention, there is provided a high capacity flexible dc converter valve surplus power overvoltage suppression system comprising:
the fault dividing module carries out global simulation scanning on all types of faults of the alternating current system, and divides the faults into three grades according to the simulation results and the measures taken: minor, moderate, and severe faults;
the slight fault processing module is used for realizing fault ride-through by means of the overvoltage tolerance capability of the equipment without adopting hardware or controlling an additional strategy for slight faults;
the medium fault processing module is used for rapidly reducing the transmitted direct current power by the transmitting end after identifying the medium fault so as to realize fault ride-through;
and for the serious fault, the receiving end rapidly enters a power rapid cut-off mode after the fault is identified, so that the transmission of surplus power on the direct current side is rapidly blocked.
In the above embodiment, the steps are classified into three levels according to the measures taken according to the simulation result, including:
taking the positive sequence voltage drop amplitude as a criterion, and taking no measures according to simulation results, wherein the fault which can be directly traversed is a slight fault, and the corresponding boundary voltage drop is Uacset1; the corresponding fault that the power supply end can pass through is a medium fault, and the corresponding boundary voltage drops to Uacset2; faults that must be in "power fast phase mode" are critical faults.
In the above embodiment, the overpressure tolerance capability of the device itself includes: short-time overload capacity and the characteristic that overvoltage and overcurrent peaks are asynchronous when voltage of the flexible direct current module fluctuates.
Short-time overload capacity, namely rapidly increasing the current of the converter valve to the maximum overload level when the alternating current is low in voltage, and increasing the dissipation of surplus power;
the characteristics that overvoltage and overcurrent peaks are asynchronous when the voltage of the flexible direct current module fluctuates are utilized, and the surplus power absorbed by an energy storage element of the converter valve is increased by utilizing the higher overvoltage capacity of the converter valve when the current is small.
In the above embodiment, for a slight fault, at least it is required to ensure that no measures are taken in case of a single-phase ground fault, and only the capability of the device itself is used to limit the overvoltage of the converter valve within a safe range, and if the overvoltage cannot be satisfied, the number of sub-modules or the module capacitance should be increased until the requirement is satisfied.
In the above embodiment, the transmitting end rapidly reduces the transmitted dc power, including:
the method comprises the steps that a sending end automatically monitors the rising of port direct current voltage, and when the port direct current voltage rises to a boundary voltage drop value Udcset1 corresponding to a slight fault, the reference value of active current in a converter control system is quickly reduced to a preset value idset1;
after the medium fault is identified by the receiving end, the medium fault is transmitted to the transmitting end converter station through inter-station communication, and the transmitting end converter station rapidly reduces the active current reference value to a preset value idset1 after receiving the rapid power reduction instruction transmitted by the receiving end.
In this embodiment, the preset value idset1 is: idset1/idN is less than Uacset2/UacN, uacset2 is a boundary voltage drop value corresponding to a medium fault, idN is a transmitting end active current rated value, and UacN is a receiving end alternating current bus voltage rated value.
In the above embodiment, the "power quick cut-off mode" includes:
for a flexible direct current system adopting a half-bridge type converter and a direct current breaker, the direct current breaker is quickly tripped to block the transmission of direct current power, and at the moment, surplus power is dissipated in a sending-end flexible direct current converter valve and an energy dissipation lightning arrester of the direct current breaker;
for a flexible direct current system adopting a full-bridge-half-bridge hybrid direct current breaker, the port direct current voltage is rapidly controlled to be 0 so as to block the direct current side power from accumulating in the converter valve, at the moment, the direct current is increased, and surplus power is converted into electromagnetic energy stored in an inductor on a direct current line.
The system provided in this embodiment is used to execute the above method embodiments, and specific flow and details refer to the above embodiments, which are not described herein.
In one embodiment of the present invention, a computing device structure is provided, which may be a terminal, and may include: a processor (processor), a communication interface (Communications Interface), a memory (memory), a display screen, and an input device. The processor, the communication interface and the memory complete communication with each other through a communication bus. The processor is configured to provide computing and control capabilities. The memory comprises a non-volatile storage medium storing an operating system and a computer program which when executed by a processor implements a method in one of the above embodiments; the internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The communication interface is used for carrying out wired or wireless communication with an external terminal, and the wireless mode can be realized through WIFI, a manager network, NFC (near field communication) or other technologies. The display screen can be a liquid crystal display screen or an electronic ink display screen, the input device can be a touch layer covered on the display screen, can also be a key, a track ball or a touch pad arranged on the shell of the computing equipment, and can also be an external keyboard, a touch pad or a mouse and the like. The processor may invoke logic instructions in memory.
Further, the logic instructions in the memory described above may be implemented in the form of software functional units and stored in a computer-readable storage medium when sold or used as a stand-alone product. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
In one embodiment of the present invention, a computer program product is provided, the computer program product comprising a computer program stored on a non-transitory computer readable storage medium, the computer program comprising program instructions which, when executed by a computer, are capable of performing the methods provided by the method embodiments described above.
In one embodiment of the present invention, a non-transitory computer readable storage medium storing server instructions that cause a computer to perform the methods provided by the above embodiments is provided.
The foregoing embodiment provides a computer readable storage medium, which has similar principles and technical effects to those of the foregoing method embodiment, and will not be described herein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. The method for inhibiting excess power overvoltage of the high-capacity flexible direct current converter valve is characterized by comprising the following steps of:
all types of faults of the alternating current system are subjected to global simulation scanning, and three grades are classified according to the adopted measures according to simulation results: minor, moderate, and severe faults;
for slight faults, hardware or control additional strategies are not needed, and fault ride-through is realized by means of the overvoltage tolerance capability of the equipment;
for medium faults, the transmitting end rapidly reduces the transmitted direct current power after identifying the faults, so as to realize fault ride-through;
for serious faults, the receiving end needs to quickly enter a power quick cut-off mode after the faults are identified, and the transmission of surplus power on the direct current side is quickly blocked.
2. The method for suppressing excess power overvoltage of a high-capacity flexible direct current converter valve according to claim 1, wherein the steps are classified into three classes according to the measures taken according to the simulation result, comprising:
taking the positive sequence voltage drop amplitude as a criterion, and taking no measures according to simulation results, wherein the fault which can be directly traversed is a slight fault, and the corresponding boundary voltage drop is Uacset1; the corresponding fault that the power supply end can pass through is a medium fault, and the corresponding boundary voltage drops to Uacset2; faults that must be in "power fast phase mode" are critical faults.
3. The method for excess power overvoltage suppression of a high capacity flexible dc converter valve according to claim 1, wherein the overvoltage tolerance capability of the device itself comprises: short-time overload capacity and the characteristic that overvoltage and overcurrent peaks are asynchronous when voltage of the flexible direct current module fluctuates;
short-time overload capacity, namely rapidly increasing the current of the converter valve to the maximum overload level when the alternating current is low in voltage, and increasing the dissipation of surplus power;
the characteristics that overvoltage and overcurrent peaks are asynchronous when the voltage of the flexible direct current module fluctuates are utilized, and the surplus power absorbed by an energy storage element of the converter valve is increased by utilizing the higher overvoltage capacity of the converter valve when the current is small.
4. The method for suppressing excess power overvoltage of a high-capacity flexible direct current converter valve according to claim 1, wherein for a slight fault, at least under the condition of single-phase ground fault, no measures are required, the overvoltage of the converter valve can be limited within a safety range only by utilizing the capacity of the equipment, and if the overvoltage cannot be satisfied, the number of sub-modules or the module capacitance is increased until the requirement is satisfied.
5. The method for suppressing excess power overvoltage of a high-capacity flexible direct current converter valve according to claim 1, wherein the transmitting end rapidly reduces the transmitted direct current power, comprising:
the method comprises the steps that a sending end automatically monitors the rising of port direct current voltage, and when the port direct current voltage rises to a boundary voltage drop value Udcset1 corresponding to a slight fault, the reference value of active current in a converter control system is quickly reduced to a preset value idset1;
after the medium fault is identified by the receiving end, the medium fault is transmitted to the transmitting end converter station through inter-station communication, and the transmitting end converter station rapidly reduces the active current reference value to a preset value idset1 after receiving the rapid power reduction instruction transmitted by the receiving end.
6. The method for suppressing excess power overvoltage of a high-capacity flexible direct current converter valve according to claim 5, wherein the preset value idset1 is: idset1/idN is less than Uacset2/UacN, uacset2 is a boundary voltage drop value corresponding to a medium fault, idN is a transmitting end active current rated value, and UacN is a receiving end alternating current bus voltage rated value.
7. The method for suppressing excess power overvoltage of a high-capacity flexible direct current converter valve according to claim 1, wherein the power quick cut-off mode comprises:
for a flexible direct current system adopting a half-bridge type converter and a direct current breaker, the direct current breaker is quickly tripped to block the transmission of direct current power, and at the moment, surplus power is dissipated in a sending-end flexible direct current converter valve and an energy dissipation lightning arrester of the direct current breaker;
for a flexible direct current system adopting a full-bridge-half-bridge hybrid direct current breaker, a receiving end rapidly controls the port direct current voltage to be 0 so as to block the direct current side power from accumulating in a converter valve, at the moment, the direct current is increased, and surplus power is converted into electromagnetic energy stored in an inductor on a direct current line.
8. The utility model provides a surplus power overvoltage suppression system of high-capacity flexible direct current converter valve which characterized in that includes:
the fault dividing module carries out global simulation scanning on all types of faults of the alternating current system, and divides the faults into three grades according to the simulation results and the measures taken: minor, moderate, and severe faults;
the slight fault processing module is used for realizing fault ride-through by means of the overvoltage tolerance capability of the equipment without adopting hardware or controlling an additional strategy for slight faults;
the medium fault processing module is used for rapidly reducing the transmitted direct current power by the transmitting end after identifying the medium fault so as to realize fault ride-through;
and for the serious fault, the receiving end rapidly enters a power rapid cut-off mode after the fault is identified, so that the transmission of surplus power on the direct current side is rapidly blocked.
9. A computer readable storage medium storing one or more programs, wherein the one or more programs comprise instructions, which when executed by a computing device, cause the computing device to perform any of the methods of claims 1-7.
10. A computing device, comprising: one or more processors, memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs comprising instructions for performing any of the methods of claims 1-7.
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