CN116345413A - Method and system for determining overvoltage and overcurrent based on phase-to-phase ground fault - Google Patents

Method and system for determining overvoltage and overcurrent based on phase-to-phase ground fault Download PDF

Info

Publication number
CN116345413A
CN116345413A CN202211266543.9A CN202211266543A CN116345413A CN 116345413 A CN116345413 A CN 116345413A CN 202211266543 A CN202211266543 A CN 202211266543A CN 116345413 A CN116345413 A CN 116345413A
Authority
CN
China
Prior art keywords
phase
current
wind power
fault
positive sequence
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202211266543.9A
Other languages
Chinese (zh)
Inventor
曹庆伟
郭小江
姚中原
申旭辉
张宇
孙栩
汤海雁
陈怡静
李春华
赵瑞斌
李铮
奚嘉雯
唐程
胡皓
曾煜君
陈翼帆
潘赫男
张钧阳
张颖
韩斯琪
胡家兵
尚磊
李英彪
林晨升
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Huaneng Power International Jiangsu Energy Development Co Ltd
Institute Of New Energy Wuhan Co ltd
Huazhong University of Science and Technology
Huaneng Clean Energy Research Institute
Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch
Shengdong Rudong Offshore Wind Power Co Ltd
Original Assignee
Huaneng Power International Jiangsu Energy Development Co Ltd
Institute Of New Energy Wuhan Co ltd
Huazhong University of Science and Technology
Huaneng Clean Energy Research Institute
Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch
Shengdong Rudong Offshore Wind Power Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huaneng Power International Jiangsu Energy Development Co Ltd, Institute Of New Energy Wuhan Co ltd, Huazhong University of Science and Technology, Huaneng Clean Energy Research Institute, Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch, Shengdong Rudong Offshore Wind Power Co Ltd filed Critical Huaneng Power International Jiangsu Energy Development Co Ltd
Priority to CN202211266543.9A priority Critical patent/CN116345413A/en
Publication of CN116345413A publication Critical patent/CN116345413A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
    • 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
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
    • 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]
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

The application provides a method and a system for determining overvoltage and overcurrent based on phase-to-phase ground fault, wherein the method comprises the following steps: respectively determining a corresponding negative sequence fault current maximum value and a corresponding non-fault phase voltage maximum value when the phase-to-phase ground fault occurs according to a total impedance value, a positive sequence voltage and an alternating current positive sequence current corresponding to the system when the phase-to-phase ground fault occurs; and taking the maximum value of the negative sequence fault current as negative sequence overcurrent when the phase-to-phase ground fault occurs, and taking the maximum value of the voltage of the non-fault phase as overvoltage when the wind power is sent out from a system through soft direct. According to the technical scheme, the negative sequence overcurrent and overvoltage values when the phase-to-phase ground fault occurs can be accurately determined according to the total impedance value, the positive sequence voltage and the alternating positive sequence current corresponding to the system when the wind power is sent out from the system through the soft direct connection, and the wind power is controlled to stably run through the soft direct connection based on the negative sequence overcurrent and overvoltage values.

Description

Method and system for determining overvoltage and overcurrent based on phase-to-phase ground fault
Technical Field
The present disclosure relates to the field of over-current and over-voltage, and more particularly, to a method and system for determining over-voltage and over-current based on an inter-phase ground fault.
Background
A high-voltage direct current transmission system (high voltage dc transmission system based on voltage source converter, VSC-HVDC) based on a voltage source converter provides an economic and efficient grid connection mode for a wind farm. The grid-connected technology of wind power through a flexible direct current output system is also one of the important focusing directions. Wind farms typically employ direct drive fans, and their grid-side converters (grid side converters, GSCs) typically employ two-level converters (two-level voltage source converters, 2L-VSCs). Modular multilevel converters (modular multilevel converter, MMC) are increasingly becoming the topology of VSC-HVDC mainstream due to their unique advantages. And interphase faults are one of the most common faults in power systems. When an alternating current system between the GSC and the transmitting end MMC has interphase faults, the system can generate larger transient over-current and over-voltage under the influence of negative sequence current. Due to the low overcurrent and low overvoltage characteristics of the power electronic devices, the system is difficult to realize fault ride-through, so that the safe and reliable operation of the system is affected. Therefore, it is of great significance to study the over-current and over-voltage characteristics under interphase faults.
Disclosure of Invention
The method and the system for determining the overvoltage and the overcurrent based on the phase-to-phase ground fault at least solve the technical problem that the system is difficult to realize fault ride-through due to the low overcurrent and low overvoltage characteristics of the power electronic device in the prior art, so that the safe and reliable operation of the system is affected.
An embodiment of a first aspect of the present application provides a method for determining an overvoltage and an overcurrent based on an indirect phase-to-earth fault, the method including:
acquiring a total impedance value corresponding to a system when the wind power is sent out from the system through a flexible direct connection and has an indirect ground fault, a positive sequence voltage output by a multi-level converter at a sending end and an alternating current positive sequence current output by a fan;
respectively determining a corresponding negative sequence fault current maximum value and a corresponding non-fault phase voltage maximum value when the wind power is subjected to phase-to-phase ground fault through a soft direct delivery system according to the total impedance value, the positive sequence voltage and the alternating current positive sequence current;
and taking the maximum value of the negative sequence fault current as negative sequence overcurrent when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system, and taking the maximum value of the voltage of the non-fault phase as overvoltage when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system.
Preferably, the method further comprises:
determining positive sequence overvoltage corresponding to a common connection point of a wind turbine in a system through flexible direct transmission when the wind power fails to phase-to-phase ground according to the total impedance value, the positive sequence voltage and the alternating current positive sequence current;
and obtaining a reactance value corresponding to a fan converter reactor in the system, and determining negative sequence overvoltage corresponding to a common connection point of the fan in the system through flexible direct transmission when the wind power fails to the ground phase according to the reactance value corresponding to the fan converter reactor, the total impedance value, the positive sequence voltage and the alternating current positive sequence current.
Preferably, the calculation formula of the negative sequence fault current maximum value is as follows:
Figure BDA0003893516990000021
wherein I is fanmax For the maximum value of the negative sequence fault current, U mp Positive sequence voltage X output by a multi-level converter at a transmitting end in a wind power soft direct transmitting system all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, I wp The alternating current positive sequence current is output by the fan.
Preferably, the calculation formula of the voltage maximum value of the non-fault phase is as follows:
Figure BDA0003893516990000022
in U famax Is the voltage maximum of the non-fault phase, U mp Positive sequence voltage X output by a multi-level converter at a transmitting end in a wind power soft direct transmitting system all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, I wp The alternating current positive sequence current is output by the fan.
Further, the calculation formula of the positive sequence overvoltage corresponding to the common connection point of the fan when the phase-to-phase ground fault occurs is as follows: u (U) wpmax ：
Figure BDA0003893516990000023
The calculation formula of the negative sequence overvoltage corresponding to the common connection point of the fan when the phase-to-phase ground fault occurs is as follows:
Figure BDA0003893516990000024
in U wpmax In order to generate positive sequence overvoltage corresponding to the common connection point of the fans when phase-to-phase ground faults occur, U wnmax Negative sequence overvoltage corresponding to common connection point of fan when phase-to-phase ground fault occurs, U mp For wind power to be sent out through flexible straight to positive sequence voltage output by a multi-level converter at a sending end in a system, I wp For the alternating current positive sequence current output by the fan, X all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, X weq And the reactance value corresponding to the fan converter reactor is alpha, and the distance from the fault point to the multi-level converter at the transmitting end in the wind power soft and direct transmitting system is alpha.
An embodiment of a second aspect of the present application provides a system for determining an overvoltage and an overcurrent based on an indirect phase ground fault, including:
the system comprises an acquisition module, a control module and a control module, wherein the acquisition module is used for acquiring a total impedance value corresponding to a system when the wind power is sent out from the system through a flexible direct transmission mode and has an indirect ground fault, a positive sequence voltage output by a multi-level converter at a transmitting end and an alternating current positive sequence current output by a fan;
the first determining module is used for respectively determining a corresponding negative sequence fault current maximum value and a corresponding non-fault phase voltage maximum value when the wind power is subjected to phase-to-phase ground fault through the flexible direct-current sending system according to the total impedance value, the positive sequence voltage and the alternating positive sequence current;
and the second determining module is used for taking the maximum value of the negative sequence fault current as negative sequence overcurrent when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system, and taking the maximum value of the voltage of the non-fault phase as overvoltage when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system.
Preferably, the determining system further comprises:
the third determining module is used for determining positive sequence overvoltage corresponding to a common connection point of the wind power generator in the system through flexible direct transmission when the wind power is in phase-to-phase ground fault according to the total impedance value, the positive sequence voltage and the alternating current positive sequence current;
and the fourth determining module is used for obtaining the reactance value corresponding to the fan converter reactor in the system, and determining the negative sequence overvoltage corresponding to the common connection point of the fan in the system through flexible direct sending of the wind power when the direct-current fault occurs according to the reactance value corresponding to the fan converter reactor, the total impedance value, the positive sequence voltage and the alternating-current positive sequence current.
Preferably, the calculation formula of the negative sequence fault current maximum value is as follows:
Figure BDA0003893516990000031
wherein I is fanmax For the maximum value of the negative sequence fault current, U mp In a soft and straight wind power delivery systemPositive sequence voltage X output by terminal multi-level converter all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, I wp The alternating current positive sequence current is output by the fan.
An embodiment of a third aspect of the present application provides an electronic device, including: a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method as described in the embodiments of the first aspect when the program is executed.
An embodiment of a fourth aspect of the present application proposes a computer readable storage medium, on which a computer program is stored, which program, when being executed by a processor, implements a method as described in an embodiment of the first aspect.
The technical scheme provided by the embodiment of the application at least brings the following beneficial effects:
the application provides a method and a system for determining overvoltage and overcurrent based on phase-to-phase ground fault, wherein the method comprises the following steps: acquiring a total impedance value corresponding to a system when the wind power is sent out from the system through a flexible direct connection and has an indirect ground fault, a positive sequence voltage output by a multi-level converter at a sending end and an alternating current positive sequence current output by a fan; respectively determining a corresponding negative sequence fault current maximum value and a corresponding non-fault phase voltage maximum value when the wind power is subjected to phase-to-phase ground fault through a soft direct delivery system according to the total impedance value, the positive sequence voltage and the alternating current positive sequence current; and taking the maximum value of the negative sequence fault current as negative sequence overcurrent when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system, and taking the maximum value of the voltage of the non-fault phase as overvoltage when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system. According to the technical scheme, the negative sequence overcurrent and overvoltage values when the phase-to-phase ground fault occurs can be accurately determined according to the total impedance value, the positive sequence voltage and the alternating positive sequence current corresponding to the system when the wind power is sent out from the system through the soft direct connection, and the wind power is controlled to stably run through the soft direct connection based on the negative sequence overcurrent and overvoltage values.
Additional aspects and advantages of the application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the application.
Drawings
The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a flow chart of a method for determining overvoltage and overcurrent based on an indirect phase to ground fault according to one embodiment of the present application;
FIG. 2 is a schematic diagram of a control process of an MMC according to one embodiment of the present application;
FIG. 3 is a schematic diagram of a control process of a GSC provided according to an embodiment of the application;
FIG. 4 is an equivalent circuit diagram of a system in full-scale mode according to one embodiment of the present application;
FIG. 5 is an equivalent circuit diagram of a system in a current limit mode according to one embodiment of the present application;
FIG. 6 is an equivalent circuit diagram of a system in the event of an a-phase earth fault provided in accordance with one embodiment of the present application;
FIG. 7 is a schematic diagram of an indirect phase to earth fault at α provided in accordance with one embodiment of the present application;
FIG. 8 is a graph of ground coefficient versus fault point provided in accordance with one embodiment of the present application;
FIG. 9 is a graph of negative sequence current coefficient versus fault point provided in accordance with one embodiment of the present application;
FIG. 10 is a graph of PCC point positive sequence voltage versus fault point for a GSC provided according to an embodiment of the application;
FIG. 11 is a schematic diagram of an equivalent circuit for phase-to-ground fault in a current limit mode according to one embodiment of the present application;
FIG. 12 is a first block diagram of a determination system based on overvoltage and overcurrent from an indirect phase to ground fault according to one embodiment of the present application;
fig. 13 is a second block diagram of a determination system for overvoltage and overcurrent based on an indirect phase ground fault according to one embodiment of the present application.
Detailed Description
Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and intended for the purpose of explaining the present application and are not to be construed as limiting the present application.
The method and the system for determining the overvoltage and the overcurrent based on the phase-to-phase ground fault, which are provided by the application, comprise the following steps: acquiring a total impedance value corresponding to a system when the wind power is sent out from the system through a flexible direct connection and has an indirect ground fault, a positive sequence voltage output by a multi-level converter at a sending end and an alternating current positive sequence current output by a fan; respectively determining a corresponding negative sequence fault current maximum value and a corresponding non-fault phase voltage maximum value when the wind power is subjected to phase-to-phase ground fault through a soft direct delivery system according to the total impedance value, the positive sequence voltage and the alternating current positive sequence current; and taking the maximum value of the negative sequence fault current as negative sequence overcurrent when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system, and taking the maximum value of the voltage of the non-fault phase as overvoltage when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system. According to the technical scheme, the negative sequence overcurrent and overvoltage values when the phase-to-phase ground fault occurs can be accurately determined according to the total impedance value, the positive sequence voltage and the alternating positive sequence current corresponding to the system when the wind power is sent out from the system through the soft direct connection, and the wind power is controlled to stably run through the soft direct connection based on the negative sequence overcurrent and overvoltage values.
The following describes a method and a system for determining overvoltage and overcurrent based on phase-to-earth fault according to the embodiments of the present application with reference to the accompanying drawings.
Example 1
Fig. 1 is a flowchart of a method for determining overvoltage and overcurrent based on an indirect earth fault according to an embodiment of the present application, as shown in fig. 1, the method includes:
step 1: acquiring a total impedance value corresponding to a system when the wind power is sent out from the system through a flexible direct connection and has an indirect ground fault, a positive sequence voltage output by a multi-level converter at a sending end and an alternating current positive sequence current output by a fan;
step 2: respectively determining a corresponding negative sequence fault current maximum value and a corresponding non-fault phase voltage maximum value when the wind power is subjected to phase-to-phase ground fault through a soft direct delivery system according to the total impedance value, the positive sequence voltage and the alternating current positive sequence current;
in the embodiment of the present disclosure, the calculation formula of the negative sequence fault current maximum value is as follows:
Figure BDA0003893516990000061
wherein I is fanmax For the maximum value of the negative sequence fault current, U mp Positive sequence voltage X output by a multi-level converter at a transmitting end in a wind power soft direct transmitting system all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, I wp The alternating current positive sequence current is output by the fan.
The voltage maximum of the non-faulty phase is calculated as follows:
Figure BDA0003893516990000062
in U famax Is the voltage maximum of the non-fault phase, U mp Positive sequence voltage X output by a multi-level converter at a transmitting end in a wind power soft direct transmitting system all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, I wp The alternating current positive sequence current is output by the fan.
Step 3: and taking the maximum value of the negative sequence fault current as negative sequence overcurrent when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system, and taking the maximum value of the voltage of the non-fault phase as overvoltage when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system.
In an embodiment of the disclosure, the method further comprises:
step 4: determining positive sequence overvoltage corresponding to a common connection point of a wind turbine in a system through flexible direct transmission when the wind power fails to phase-to-phase ground according to the total impedance value, the positive sequence voltage and the alternating current positive sequence current;
step 5: and obtaining a reactance value corresponding to a fan converter reactor in the system, and determining negative sequence overvoltage corresponding to a common connection point of the fan in the system through flexible direct transmission when the wind power fails to the ground phase according to the reactance value corresponding to the fan converter reactor, the total impedance value, the positive sequence voltage and the alternating current positive sequence current.
Further, the calculation formula of the positive sequence overvoltage corresponding to the common connection point of the fan when the phase-to-phase ground fault occurs is as follows: u (U) wpmax ：
Figure BDA0003893516990000063
The calculation formula of the negative sequence overvoltage corresponding to the common connection point of the fan when the phase-to-phase ground fault occurs is as follows:
Figure BDA0003893516990000064
in U wpmax In order to generate positive sequence overvoltage corresponding to the common connection point of the fans when phase-to-phase ground faults occur, U wnmax Negative sequence overvoltage corresponding to common connection point of fan when phase-to-phase ground fault occurs, U mp For wind power to be sent out through flexible straight to positive sequence voltage output by a multi-level converter at a sending end in a system, I wp For the alternating current positive sequence current output by the fan, X all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, X weq Converter reactor for fanAnd the corresponding reactance value alpha is the distance from the fault point to the multi-level converter at the transmitting end in the wind power transmission system through flexible straight transmission.
In the embodiments of the present disclosure, to simplify the analysis, a wind farm may be equivalently one GSC; the MMC and the GSC adopt a double closed-loop control strategy, comprising a voltage outer loop and a current inner loop, and meanwhile, in order to control the negative sequence current, the negative sequence control is respectively added into the MMC and the GSC.
The control process of the MMC is as shown in fig. 2:
MMC adopts the traditional VF control strategy, firstly, a controller directly integrates time by 50Hz frequency to generate the phase angle theta of MMC modulation voltage MMC This phase angle is sent to Park transforms (T abc/dq ) And inverse Park transform (T dq/abc ) In the module, collect current I of MMC m And PCC point voltage U ms Separating positive and negative sequence components and d and q axis components respectively to obtain I mdqp 、I mdqn 、U msdqp 、U msdqn The PCC point voltage positive sequence component U msdqp Comparing with the reference value, inputting the error amount into the PI controller to obtain the command value of the positive sequence current, and then inputting the positive sequence current I mdqp Comparing the command value with the error value, inputting the error value into the PI controller, and adding/subtracting the cross-coupling term (ωL) eq I mdqp ) And a voltage feedforward term (U msdqp ) Thereby generating a positive-sequence modulation voltage, and then generating an actual positive-sequence modulation voltage U by passing the modulation voltage through a positive-sequence modulation voltage limiter mcdqp * . Similarly, the negative sequence control only maintains the inner loop control strategy, and the negative sequence current I mdqn Comparing the command value with the error value, inputting the error value into the PI controller, and adding/subtracting the cross-coupling term (ωL) eq I mdqn ) And a voltage feedforward term (U msdqn ) Thereby generating a negative sequence modulation voltage U mcdqn * . The positive and negative sequence modulated voltages are converted by inverse Park (T dq/abc ) Thereafter, three-phase modulation voltages are generated. In the figure, U mc For MMC AC outlet voltage, U ms For its PCC point voltage, I m Is MMC alternating voltage, U wc For GSC AC outlet voltage, U ws For its PCC point voltage, I w For GSC AC voltage, I dc 、u mdc GSC DC side current and MMC DC side voltage, θ MMC 、θ VSC Phase angles, X, of MMC and GSC side PCC points, respectively line For AC transmission line impedance, X w And X m Impedance from failure point to GSC outlet and failure point to MMC outlet, respectively, X weq And X meq The converter reactors are GSC and MMC respectively.
Wherein, as shown in FIG. 3, the GSC adopts a following-net control strategy, firstly, the positive sequence voltage phase theta of the fan PCC point is collected by a phase-locked loop (PLL) VSC The phase angle is fed to Park transform (T abc/dq ) And inverse Park transform (T dq/abc ) In the module, collecting the current of GSC and PCC point voltage, separating positive and negative sequence components and d and q axis components respectively as I wdqp 、I wdqn 、U wsdqp 、U wsdqn Secondly, the DC voltage U of GSC wdc Comparing with the reference value, inputting the error amount into the PI controller to obtain the command value of the positive sequence current, and then outputting the positive sequence current I wdqp Comparing the command value with the error value, inputting the error value into the PI controller, and adding/subtracting the cross-coupling term (ωLI wdqp ) And a voltage feedforward term (U wsdqp ) Thereby generating a positive sequence modulation voltage. Similarly, the negative sequence control only maintains the inner loop control strategy, and the negative sequence current I wdqn Comparing the command value with the error value, inputting the error value into the PI controller, and adding/subtracting the cross-coupling term (ωLI wdqn ) And a voltage feedforward term (U wsdqn ) Thereby generating a negative sequence modulated voltage. The positive and negative sequence modulated voltages are converted by inverse Park (T dq/abc ) After that, three-phase modulation voltage U is generated wcp * And U wcn *。
When shallow faults occur, the MMC outputs positive sequence current which is smaller than the current limiting value, and the MMC is in a full modulation mode and can be equivalently used as a voltage source; when a deep fault occurs, the MMC outputs positive sequence current to be limited to a limiting value, and the MMC is in a current limiting mode and can be equivalently regarded as currentA source, while GSC may be equivalently a current source. Wherein, the system equivalent circuit without considering the negative sequence control and in the full-tuning mode is shown in figure 4, the system equivalent circuit without considering the negative sequence control and in the current limiting mode is shown in figure 5, in the figure, U mcplim And I mlim Respectively an MMC positive sequence voltage limit value and an MMC total current limit value, U wc For MMC AC outlet voltage, X w For the impedance from the fault point to the GSC outlet, I w Is GSC AC current, I m Is MMC alternating current, X m For the impedance from the fault point to the MMC outlet, f (n) Is the failure point.
The following description is made regarding the full modulation mode:
the key to realizing phase-to-phase ground fault ride-through is to acquire key influencing factors of system overvoltage and overcurrent. Therefore, the invention adopts an analysis method of decoupling circuit characteristics and control characteristics, ignores the negative sequence control of MMC and GSC to obtain the expressions of the overcurrent and overvoltage of the system, and extracts key influencing factors therein.
When the system has two-phase ground fault, taking the b-phase and c-phase faults as examples, and neglecting the system resistance, the equivalent circuit of the system is shown in FIG. 6, wherein the calculation formula of the fault current can be as follows
Figure BDA0003893516990000081
Wherein I is fap Positive sequence current of system when b phase and c phase have ground fault, I fan Negative sequence current of system when b phase and c have ground fault, U mp For the positive sequence voltage output by the multi-level converter at the transmitting end in the system, < >>
Figure BDA0003893516990000082
X mn For the negative sequence component of the impedance from the fault point to the MMC outlet, X wn As the negative sequence component of the impedance from the fault point to the GSC outlet, in a system, the transformer is typically directly grounded, so the present invention assumes that the positive, negative, and zero sequence impedances in the system are the same. When an indirect earth fault occurs at alpha, X as shown in FIG. 7 mp 、X n ' can be expressed as +.>
Figure BDA0003893516990000083
Wherein X is mp For positive sequence component of impedance from fault point to MMC outlet, X all All reactance from the GSC AC outlet to the MMC AC outlet is represented, including MMC converter reactors, line reactance, GSC filters and their converter reactors. Let formula->
Figure BDA0003893516990000084
Substituted into->
Figure BDA0003893516990000085
In the system, it can be found that when GSC output current lags MMC output voltage by 90 DEG, namely the fan only emits reactive power, the negative sequence current in the system reaches the maximum value of +.>
Figure BDA0003893516990000091
Let formula->
Figure BDA0003893516990000092
Substitution into
Figure BDA0003893516990000093
In (3) finishing to obtain->
Figure BDA0003893516990000094
Wherein k is i Is a negative sequence current coefficient, and the expression is +.>
Figure BDA0003893516990000095
Meanwhile, according to the operation characteristics of the power grid, transient overvoltage can occur to a non-fault phase, the overvoltage level of a fault point is highest, and the problem that a fan is disconnected due to overvoltage is also considered by PCC points of GSC.
The sound phase voltage (a phase) of the fault point is U fa ＝U fap +U fan +U fa0 ＝2jI fap X n ' the sound phase amplitude of the fault point is U fa ＝k u (U mp +αI wp X all ) Wherein ku is the inter-phase short circuit grounding coefficient，
Figure BDA0003893516990000096
The fault point sound phase voltage is maximum and U is obtained when the GSC output current lags behind the MMC voltage by 90 DEG, namely when the GSC only sends reactive power famax ＝k u (U mp +αI wp X all ) The PCC point positive sequence voltage and the negative sequence voltage of the GSC are U wp ＝-I fn X n '+I wp X wp ，U wn ＝αjI fn X weq It can be seen that when the GSC output current lags behind the MMC voltage by 90 DEG, i.e. the GSC only emits reactive power, the positive and negative sequence voltage amplitude is at most
Figure BDA0003893516990000097
Further, based on the relationship between the ground coefficient and the fault point α as shown in fig. 8, the relationship between the negative sequence current coefficient and the fault point α as shown in fig. 9, and the relationship between the positive sequence voltage of the PCC point of the GSC and the fault point α as shown in fig. 10, it is possible to obtain: when GSC positive sequence current lags MMC positive sequence voltage by 90 degrees, the overvoltage and overcurrent level of the system are highest; the closer the fault point is to the MMC, the higher the system overvoltage and overcurrent levels are; negative sequence current level and overvoltage level of system and GSC positive sequence current I wp Related to the following.
The following description is made regarding the current limit mode:
when the alternating current system has a deep fault, the fault current reaches the MMC current limiting value, and at the moment, the MMC presents the current source characteristic and is in the current limiting mode. The system overvoltage is significantly lower in the current limit mode than in the full modulation mode, so that the system overvoltage level is not analyzed in the current limit mode. However, in the current limiting mode, the MMC output current is equal to the current limiter limiting value, reaches the upper limit of system protection, is larger than the current in the full modulation mode, the negative sequence current is further increased, and the problem of over-current of an MMC bridge arm is further aggravated.
The equivalent circuit of the phase-to-phase ground fault in the current limiting mode is shown in FIG. 11, and the phase-to-phase ground fault negative sequence current is
Figure BDA0003893516990000101
It can be seen that the magnitude of the system negative sequence current is independent of the fault location, and only related to the MMC and GSC output current magnitude and phase. When the GSC output current is in phase with the MMC output current, namely the GSC only sends out reactive power, the negative sequence current of the system is maximum. In the current limit mode, the negative sequence current at the time of the phase-to-phase ground short fault can be reduced to some extent by reducing the positive sequence current in the system, as in the full modulation mode.
In summary, the method for determining the overvoltage and the overcurrent based on the phase-to-earth fault provided by the application can accurately determine the negative sequence overcurrent and the overvoltage value when the phase-to-earth fault occurs according to the total impedance value, the positive sequence voltage and the alternating positive sequence current corresponding to the system when the wind power is sent out from the system through the soft direct transmission, and control the stable operation of the wind power sent out from the system through the soft direct transmission based on the determined negative sequence overcurrent and overvoltage value.
Example two
Figure 12 is a schematic diagram of a system for determining overvoltage and overcurrent based on an indirect phase to ground fault according to one embodiment of the present application, as shown in fig. 12, includes:
the acquisition module 100 is used for acquiring a total impedance value corresponding to a system when the wind power is sent out from the system through a flexible direct connection and has an indirect ground fault, a positive sequence voltage output by a multi-level converter at a sending end and an alternating current positive sequence current output by a fan;
the first determining module 200 is configured to determine, according to the total impedance value, the positive sequence voltage and the ac positive sequence current, a negative sequence fault current maximum value and a non-fault phase voltage maximum value corresponding to when the wind power is sent out from the system through the flexible direct current to generate an indirect phase ground fault;
the second determining module 300 is configured to use the maximum value of the negative sequence fault current as a negative sequence overcurrent when the wind power is indirectly faulted by a soft direct delivery system, and use the maximum value of the voltage of the non-fault phase as an overvoltage when the wind power is indirectly faulted by the soft direct delivery system.
In an embodiment of the present disclosure, as shown in fig. 13, the determining system further includes:
a third determining module 400, configured to determine, according to the total impedance value, the positive sequence voltage, and the ac positive sequence current, a positive sequence overvoltage corresponding to a common connection point of a wind turbine in the wind power soft direct delivery system when an indirect ground fault occurs;
and a fourth determining module 500, configured to obtain a reactance value corresponding to a fan converter reactor in the system, and determine, according to the reactance value corresponding to the fan converter reactor, the total impedance value, the positive sequence voltage, and the alternating current positive sequence current, that a negative sequence overvoltage corresponding to a common connection point of the fan in the system occurs when a relative ground fault occurs, where the wind power is sent out through a flexible direct.
In the embodiment of the present disclosure, the calculation formula of the negative sequence fault current maximum value is as follows:
Figure BDA0003893516990000102
wherein I is fanmax For the maximum value of the negative sequence fault current, U mp Positive sequence voltage X output by a multi-level converter at a transmitting end in a wind power soft direct transmitting system all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, I wp The alternating current positive sequence current is output by the fan.
In an embodiment of the disclosure, the calculation formula of the voltage maximum value of the non-fault phase is as follows:
Figure BDA0003893516990000111
in U famax Is the voltage maximum of the non-fault phase, U mp Positive sequence voltage X output by a multi-level converter at a transmitting end in a wind power soft direct transmitting system all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, I wp The output of the fan isA positive sequence current flows.
Further, the calculation formula of the positive sequence overvoltage corresponding to the common connection point of the fan when the phase-to-phase ground fault occurs is as follows: u (U) wpmax ：
Figure BDA0003893516990000112
The calculation formula of the negative sequence overvoltage corresponding to the common connection point of the fan when the phase-to-phase ground fault occurs is as follows:
Figure BDA0003893516990000113
in U wpmax In order to generate positive sequence overvoltage corresponding to the common connection point of the fans when phase-to-phase ground faults occur, U wnmax Negative sequence overvoltage corresponding to common connection point of fan when phase-to-phase ground fault occurs, U mp The wind power is sent out from the positive sequence voltage output by the multi-level converter at the sending end in the system through soft direct, I wp For the alternating current positive sequence current output by the fan, X all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, X weq And the reactance value corresponding to the fan converter reactor is alpha, and the distance from the fault point to the multi-level converter at the transmitting end in the wind power soft and direct transmitting system is alpha.
In summary, according to the above-mentioned determination system based on the phase-to-earth fault and the over-current, the technical scheme provided by the application can accurately determine the negative sequence over-current and the over-voltage value when the phase-to-earth fault occurs according to the total impedance value, the positive sequence voltage and the alternating positive sequence current corresponding to the system when the wind power is subjected to the phase-to-earth fault through the soft direct delivery system, and control the stable operation of the wind power through the soft direct delivery system based on the determination of the negative sequence over-current and the over-voltage value.
Example III
In order to achieve the above embodiments, the present disclosure further proposes an electronic device including: a memory, a processor, and a computer program stored on the memory and executable on the processor, which when executed, implements the method as described in embodiment one.
Example IV
In order to implement the above-mentioned embodiments, the present disclosure also proposes a computer-readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements the method according to the first embodiment.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and additional implementations are included within the scope of the preferred embodiment of the present application in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the embodiments of the present application.
Although embodiments of the present application have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the application, and that variations, modifications, alternatives, and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the application.

Claims (10)

1. A method for determining overvoltage and overcurrent based on phase-to-phase ground faults, the method comprising:
acquiring a total impedance value corresponding to a system when the wind power is sent out from the system through a flexible direct connection and has an indirect ground fault, a positive sequence voltage output by a multi-level converter at a sending end and an alternating current positive sequence current output by a fan;
respectively determining a corresponding negative sequence fault current maximum value and a corresponding non-fault phase voltage maximum value when the wind power is subjected to phase-to-phase ground fault through a soft direct delivery system according to the total impedance value, the positive sequence voltage and the alternating current positive sequence current;
and taking the maximum value of the negative sequence fault current as negative sequence overcurrent when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system, and taking the maximum value of the voltage of the non-fault phase as overvoltage when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system.
2. The method of claim 1, wherein the method further comprises:
determining positive sequence overvoltage corresponding to a common connection point of a wind turbine in a system through flexible direct transmission when the wind power fails to phase-to-phase ground according to the total impedance value, the positive sequence voltage and the alternating current positive sequence current;
and obtaining a reactance value corresponding to a fan converter reactor in the system, and determining negative sequence overvoltage corresponding to a common connection point of the fan in the system through flexible direct transmission when the wind power fails to the ground phase according to the reactance value corresponding to the fan converter reactor, the total impedance value, the positive sequence voltage and the alternating current positive sequence current.
3. The method of claim 1, wherein the negative sequence fault current maximum is calculated as:
Figure FDA0003893516980000011
wherein I is fanmax For the maximum value of the negative sequence fault current, U mp Positive sequence voltage X output by a multi-level converter at a transmitting end in a wind power soft direct transmitting system all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, I wp The alternating current positive sequence current is output by the fan.
4. The method of claim 1, wherein the voltage maximum for the non-faulted phase is calculated as:
Figure FDA0003893516980000012
in U famax Is the voltage maximum of the non-fault phase, U mp Positive sequence voltage X output by a multi-level converter at a transmitting end in a wind power soft direct transmitting system all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, I wp The alternating current positive sequence current is output by the fan.
5. The method of claim 2, wherein the positive sequence overvoltage corresponding to the fan common connection point when the phase-to-phase ground fault occurs is calculated as follows: u (U) wpmax ：
Figure FDA0003893516980000021
The calculation formula of the negative sequence overvoltage corresponding to the common connection point of the fan when the phase-to-phase ground fault occurs is as follows:
Figure FDA0003893516980000022
in U wpmax In order to generate positive sequence overvoltage corresponding to the common connection point of the fans when phase-to-phase ground faults occur, U wnmax Negative sequence overvoltage corresponding to common connection point of fan when phase-to-phase ground fault occurs, U mp For wind power to be sent out through flexible straight to positive sequence voltage output by a multi-level converter at a sending end in a system, I wp For the alternating current positive sequence current output by the fan, X all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, X weq And the reactance value corresponding to the fan converter reactor is alpha, and the distance from the fault point to the multi-level converter at the transmitting end in the wind power soft and direct transmitting system is alpha.
6. A system for determining overvoltage and overcurrent based on phase-to-earth faults, comprising:
the system comprises an acquisition module, a control module and a control module, wherein the acquisition module is used for acquiring a total impedance value corresponding to a system when the wind power is sent out from the system through a flexible direct transmission mode and has an indirect ground fault, a positive sequence voltage output by a multi-level converter at a transmitting end and an alternating current positive sequence current output by a fan;
the first determining module is used for respectively determining a corresponding negative sequence fault current maximum value and a corresponding non-fault phase voltage maximum value when the wind power is subjected to phase-to-phase ground fault through the flexible direct-current sending system according to the total impedance value, the positive sequence voltage and the alternating positive sequence current;
and the second determining module is used for taking the maximum value of the negative sequence fault current as negative sequence overcurrent when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system, and taking the maximum value of the voltage of the non-fault phase as overvoltage when the wind power is subjected to phase-to-phase ground fault through the soft direct delivery system.
7. The determination system of claim 6, wherein the determination system further comprises:
the third determining module is used for determining positive sequence overvoltage corresponding to a common connection point of the wind power generator in the system through flexible direct transmission when the wind power is in phase-to-phase ground fault according to the total impedance value, the positive sequence voltage and the alternating current positive sequence current;
and the fourth determining module is used for obtaining the reactance value corresponding to the fan converter reactor in the system, and determining the negative sequence overvoltage corresponding to the common connection point of the fan in the system through flexible direct sending of the wind power when the direct-current fault occurs according to the reactance value corresponding to the fan converter reactor, the total impedance value, the positive sequence voltage and the alternating-current positive sequence current.
8. The determination system of claim 6 wherein the negative sequence fault current maximum is calculated as:
Figure FDA0003893516980000023
wherein I is fanmax For the maximum value of the negative sequence fault current, U mp Positive sequence voltage X output by a multi-level converter at a transmitting end in a wind power soft direct transmitting system all For the total reactance value corresponding to the wind power soft and straight delivery system, alpha is the distance from the fault point to the multi-level converter at the delivery end in the wind power soft and straight delivery system, I wp The alternating current positive sequence current is output by the fan.
9. An electronic device, comprising: memory, a processor and a computer program stored on the memory and executable on the processor, which processor, when executing the program, implements the method according to any one of claims 1 to 5.
10. A computer readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements the method according to any one of claims 1 to 5.
CN202211266543.9A 2022-10-17 2022-10-17 Method and system for determining overvoltage and overcurrent based on phase-to-phase ground fault Pending CN116345413A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202211266543.9A CN116345413A (en) 2022-10-17 2022-10-17 Method and system for determining overvoltage and overcurrent based on phase-to-phase ground fault

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202211266543.9A CN116345413A (en) 2022-10-17 2022-10-17 Method and system for determining overvoltage and overcurrent based on phase-to-phase ground fault

Publications (1)

Publication Number Publication Date
CN116345413A true CN116345413A (en) 2023-06-27

Family

ID=86875279

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202211266543.9A Pending CN116345413A (en) 2022-10-17 2022-10-17 Method and system for determining overvoltage and overcurrent based on phase-to-phase ground fault

Country Status (1)

Country Link
CN (1) CN116345413A (en)

Similar Documents

Publication Publication Date Title
CN105375532B (en) A kind of fault phase-selecting method suitable for double-fed fan motor field interconnection
Kirakosyan et al. Fault ride through and grid support topology for the VSC-HVDC connected offshore wind farms
Du The control of VSC-HVDC and its use for large industrial power systems
CN109347144B (en) Low voltage ride through method of wind power flexible direct current output system
CN112398156B (en) Marine wind power system fault joint traversing method based on soft-direct MMC converter
CN111969567B (en) Series-parallel direct current transmission system receiving end alternating current fault processing method and system
CN113193586B (en) Flexible direct current compensation control method and system
Wang et al. A comprehensive improved coordinated control strategy for a STATCOM integrated HVDC system with enhanced steady/transient state behaviors
Zhou et al. Characteristic investigation and overvoltage suppression of MMC-HVDC integrated offshore wind farms under onshore valve-side SPG fault
CN111799751A (en) Flexible controller direct current unit fault current calculation method and system
CN114447984A (en) Low-voltage ride-through control method suitable for offshore wind power collection line fault and application
CN111814102A (en) Harmonic parameter optimization method suitable for offshore wind power transmission system through alternating current submarine cable network
CN115833213A (en) Method and system for determining single-phase fault characteristics of grid connection of wind power through flexible direct-current power transmission
Borges Davi et al. Fault current and fault voltage analysis of power transmission systems with high penetration of inverter-based wind generators.
Davi et al. Impacts of inverter-interfaced wind power plants in the phase-selection and directional protection functions
CN115149577B (en) Double-fed asynchronous wind driven generator transient overvoltage suppression method considering phase jump
CN115825539B (en) Method and system for determining voltage and current of wind power grid-connected two-phase ground fault
CN116345413A (en) Method and system for determining overvoltage and overcurrent based on phase-to-phase ground fault
CN113991734B (en) Doubly-fed wind turbine generator control system and method with high voltage ride through capability
CN114268120B (en) MMC alternating current side near-end asymmetric fault short-circuit current calculation method
Yuan et al. FRT improvement strategy for offshore wind farm considering operation state
CN116131294B (en) Control method and system for asymmetric alternating current fault ride through
Amarís Power Quality Solutions for Voltage Dip compensation at wind farms
Zhang et al. A MMC Topology with AC Short-Circuit Fault Ride-Through Capability and its Control Strategies
Barra et al. Comparison Between Two-Level and Modular Multilevel Converters in High Voltage Direct Current Systems Under Fault Conditions

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination