CN116148589B - Simplified analysis method and system for fault current of low-frequency power transmission system - Google Patents

Simplified analysis method and system for fault current of low-frequency power transmission system Download PDF

Info

Publication number
CN116148589B
CN116148589B CN202211437213.1A CN202211437213A CN116148589B CN 116148589 B CN116148589 B CN 116148589B CN 202211437213 A CN202211437213 A CN 202211437213A CN 116148589 B CN116148589 B CN 116148589B
Authority
CN
China
Prior art keywords
current
fault current
fault
equivalent
inductance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202211437213.1A
Other languages
Chinese (zh)
Other versions
CN116148589A (en
Inventor
向念文
叶寿洪
王书来
陆翌
裘鹏
林进钿
韩彬
赵国亮
乔光尧
赵泽昕
倪晓军
丁超
倪嘉伟
柯一帆
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.)
State Grid Smart Grid Research Institute Co ltd
China Electric Power Research Institute Co Ltd CEPRI
Hefei University of Technology
Electric Power Research Institute of State Grid Zhejiang Electric Power Co Ltd
Original Assignee
State Grid Smart Grid Research Institute Co ltd
China Electric Power Research Institute Co Ltd CEPRI
Hefei University of Technology
Electric Power Research Institute of State Grid Zhejiang Electric 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 State Grid Smart Grid Research Institute Co ltd, China Electric Power Research Institute Co Ltd CEPRI, Hefei University of Technology, Electric Power Research Institute of State Grid Zhejiang Electric Power Co Ltd filed Critical State Grid Smart Grid Research Institute Co ltd
Priority to CN202211437213.1A priority Critical patent/CN116148589B/en
Publication of CN116148589A publication Critical patent/CN116148589A/en
Application granted granted Critical
Publication of CN116148589B publication Critical patent/CN116148589B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/088—Aspects of digital computing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/58—Testing of lines, cables or conductors
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
    • Y04S10/52—Outage or fault management, e.g. fault detection or location

Abstract

The invention provides a simplified analysis method and a simplified analysis system for fault current of a low-frequency power transmission system, wherein the fault current is three-phase grounding fault current, and belongs to the technical field of power system fault protection. The method comprises the following steps: detecting a system which normally operates to obtain element inherent parameters and normal operation parameters of the system; the evolution process of the fault current is divided into three stages: charging a pre-converter-latch capacitor, discharging the pre-converter-latch capacitor, and charging a post-converter-latch capacitor; and respectively equating the fault loops of the three stages into RLC equivalent circuits, deducing a fault current analytic formula by the RLC equivalent circuits, and synthesizing to obtain the fault current analytic formula. The method can realize the three-phase grounding fault current simplified analysis calculation of the low-frequency power transmission system based on M3C without complex modeling simulation, can provide basis for relay protection setting calculation and electrical equipment selection verification, and has short calculation time and wide applicability.

Description

Simplified analysis method and system for fault current of low-frequency power transmission system
Technical Field
The invention relates to the technical field of power system fault protection, in particular to a low-frequency power transmission system fault current simplified analysis method and system, wherein the fault current is three-phase grounding fault current.
Background
The low-frequency power transmission is an alternating current power transmission mode with the transmission frequency lower than the power frequency (50/60 Hz), has the advantages of strong line power transmission capability, zero-crossing on-off of current and easiness in networking, and has unique advantages when applied to middle-distance offshore wind power. The key link of low-frequency power transmission is that an alternating-current-alternating-current frequency converter is utilized to conduct different-frequency energy interaction between a low-frequency system and a power frequency system, a modularized multi-level matrix converter (M3C) is an alternating-current converter which is currently suitable for a low-frequency power transmission technology, a full-bridge submodule cascading technology is adopted to achieve direct-current-link-free alternating-current exchange flow, and after a three-phase grounding fault occurs in a converter station, the peak value of current flowing through a submodule is far higher than a steady-state value, so that safe and stable operation of the whole system is seriously threatened.
M3C was proposed in 2001, and its theory has tended to mature over 20 years of research and improvement. Many researches on device-level control strategies of M3C have been carried out, mainly around sub-module capacitance voltage balance control, control under the unbalanced working condition of power grid voltage, flexible start-stop strategies and the like, but few researches on electromagnetic transient processes of M3C after faults are involved. The fault current path and the change rule are required to be comprehensively analyzed, the fault current analysis type of the bridge arm before and after the locking of the converter is deduced, key factors influencing the overcurrent and the overvoltage of the sub-module are analyzed, and references are provided for planning and designing the power system, relay protection setting calculation and electrical equipment selection verification.
The transient behavior research method after the M3C fault can refer to a flexible direct current transmission system based on a modularized multi-level converter (MMC), and domestic and foreign scholars can conduct a great deal of researches on the grounding fault of the flexible direct current transmission system under the alternating current and direct current side, including researches on the submodule discharging mechanism, the short circuit path and the bridge arm current change during the fault, and deduces corresponding fault current analysis type.
The Chinese patent application publication CN 103825267A discloses a method for calculating short-circuit current at MMC-MTDC direct current side in 5 months and 28 days of 2014, wherein the calculated steady-state operation current is taken as the steady-state component of the short-circuit current; solving fault components of short-circuit current according to the MMC equivalent passive circuit, the direct-current transmission line and a direct-current voltage source equivalent calculation network of the fault point; and finally, adding the steady-state component and the fault component to obtain a final short-circuit current calculation result, so that a system model can be greatly simplified, and the calculation efficiency is remarkably improved.
According to the bipolar short-circuit fault current calculation method of the HVDC system based on MMC disclosed in the Chinese patent application publication No. CN 106407494A of 2017, 2 and 15, the discharging process is equivalent according to the fault current component and the discharging current generation mechanism, and an adjusting factor is introduced to fit the curve of the discharging current, so that a final discharging current calculation formula is obtained.
The current fault current analysis method mainly aims at fault current analysis of an MMC-HVDC system, but M3C is different from the MMC in topological structure and operation state, the operation characteristic of the converter after faults is greatly changed, the number of full-bridge submodules conducted by bridge arms in the converter is not a fixed value, the electromagnetic transient process is complex after three-phase grounding faults occur, and fault current out-of-limit is likely to cause damage to power electronic devices in the converter, so that analysis calculation is needed for fault current after faults of a low-frequency power transmission system based on M3C, and then targeted fault current limiting measures are adopted.
Disclosure of Invention
The invention aims to solve the technical problem of simplifying a complex electromagnetic transient process after an M3C converter fails, and overcomes the defect that the existing fault current analysis method cannot be suitable for solving the fault current of a novel low-frequency power transmission system, so that the invention provides the fault current simplification analysis method and system for the low-frequency power transmission system, and the change trend of the fault current in a period of time after the fault occurs is rapidly represented by analyzing and calculating an RLC equivalent circuit of a fault loop.
The invention aims to achieve the purpose, and provides a simplified analysis method for fault current of a low-frequency power transmission system, wherein the fault current is three-phase grounding fault current, and the simplified analysis method comprises the following steps:
obtaining peak value U of three-phase output voltage of M3C converter by sampling s Angular frequency ω, s is phase sequence, s=a, b, c;
according to the state of the M3C converter when the fault occurs, the fault loop in the evolution process of the fault current is equivalent to a pre-charge RLC equivalent circuit, a discharge RLC equivalent circuit and a post-charge RLC equivalent circuit, and according to the peak value U s Three fault current analysis methods are established by the angular frequency omega and the three RLC equivalent circuits, and the fault current i of the pre-charging stage is calculated f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 ；
According to the fault current i of the pre-charge phase f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 Obtaining fault current i at any fault occurrence time t after fault f 。
Preferably, the fault current i at any fault occurrence time t after the fault f The analytical formula of (2) is as follows:
wherein t is 0 For the starting time of the pre-charge phase, t 1 For the start time of the discharge phase, t 2 To start the post-charge phase, t 3 Is the end time of the post-charge phase.
Preferably, the fault current i of the pre-charge phase f1 The solving process of (2) is as follows:
the pre-charging RLC equivalent circuit is an alternating current power supply u s Current limiting resistor R, first equivalent capacitor C in low frequency power transmission system e And equivalent inductance L e A loop formed by the first equivalent capacitance C e Is connected with an alternating current power supply u s First equivalent capacitance C e Is connected with equivalent inductance L by negative electrode e Equivalent inductance L e The other end of the current limiting resistor R is connected with the alternating current power supply u s The current passing through the loop is the fault current i of the pre-charge stage f1 The method comprises the steps of carrying out a first treatment on the surface of the The resistance value of the current limiting resistor R is recorded as R eq ；
The fault current analysis of the pre-charging stage is as follows:
wherein, gamma 1 Additional phase of fault current for the pre-charge phase, Z 1 The impedance of the pre-charge RLC equivalent circuit is calculated by:
wherein C is eq For the first equivalent capacitance C e Capacitance value C of (C) eq ＝9C 0 /N，L eq Is equivalent to inductance L e Inductance value L of (1) eq ＝L arm /3+L k N is the number of full-bridge sub-modules in a single bridge arm in the M3C converter, C 0 Is the capacitance value L of an energy storage capacitor C in the M3C converter arm Is the inductance value L of the bridge arm inductance L1 in the M3C converter, L k The inductance value of the line inductance L2 in the low-frequency power transmission system.
Preferably, the fault current i of the discharge phase f2 The solving process of (2) is as follows:
fault current i of the discharge phase f2 By capacitive discharge current i c And an alternating-current side short-circuit current i s The expression of the synthesized product is:
i f2 ＝i C +1 s
the discharging RLC equivalent circuit comprises a capacitor discharging RLC equivalent circuit and an alternating current short circuit RLC equivalent circuit;
the capacitor discharging RLC equivalent circuit is composed of a current-limiting resistor R and a first equivalent capacitor C in a low-frequency power transmission system e And equivalent inductance L e A loop formed by the first equivalent capacitance C e Is connected with equivalent inductance L by positive electrode e Equivalent inductance L e The other end of the current limiting resistor R is connected with the first equivalent capacitor C e The current passing through the circuit is the capacitor discharge current i c The method comprises the steps of carrying out a first treatment on the surface of the The resistance value of the current limiting resistor R is recorded as R eq ；
The AC short circuit RLC equivalent circuit is an AC power supply u s Current limiting resistor R and equivalent inductance L in low-frequency power transmission system e A loop formed by the same, wherein the equivalent inductance L e Is connected with an alternating current power supply u s . The other end of the current limiting resistor R is connected with the alternating current power supply u s The current passing through the loop is an alternating-current side short-circuit current i s ；
The fault current analysis of the discharging stage is as follows:
wherein C is eq For the first equivalent capacitance C e Capacitance value C of (C) eq ＝9C 0 N, N is the number of full-bridge sub-modules in a single bridge arm in the M3C converter, C 0 The capacitance value of the energy storage capacitor C in the M3C converter;
τ is a time constant, A is a constant coefficient, ω i Is the angular frequency of the capacitor discharge current, theta is the phase angle of the capacitor discharge current, gamma 2 For additional phase of short-circuit current at AC side, Z 2 The impedance of the circuit is the equivalent circuit of the AC short circuit RLC, and the calculation is respectively as follows:
τ＝2L eq /R eq
in U m Is the voltage at the energy storage capacitor C during the normal operation of the low-frequency power transmission system, I m Is the current at the energy storage capacitor C and L when the low-frequency power transmission system is in normal operation eq Is equivalent to inductance L e Inductance value L of (1) eq ＝L arm /3+L k ，L arm Is the inductance value L of the bridge arm inductance L1 in the M3C converter, L k The inductance value of the line inductance L2 in the low-frequency power transmission system.
Preferably, the fault current i of the post-charge phase f3 The solving process of (2) is as follows:
the back charging RLC equivalent circuit is an AC power supply u s Current limiting resistor R, second equivalent capacitor C in low frequency power transmission system e ' and equivalent inductance L e A loop formed by the second equivalent capacitance C e ' the positive electrode is connected with an alternating current power supply u s Second equivalent capacitance C e ' negative electrode connected equivalent inductance L e Equivalent inductance L e The other end of the current limiting resistor R is connected with the power supply u s The current passing through the loop is the fault current i of the post-charging stage f3 The method comprises the steps of carrying out a first treatment on the surface of the The resistance value of the current limiting resistor R is recorded as R eq ；
The fault current analysis of the post-charging stage is as follows:
wherein, gamma 3 Additional phase of fault current for post-charge phase, Z 3 The impedance of the RLC equivalent circuit for post-charge is calculated by:
wherein C' eq Is the second equivalent capacitance C e Capacitance of 'C' eq ＝3C 0 /N，L eq Is equivalent to inductance L e Inductance value L of (1) eq ＝L arm /3+L k N is the number of full-bridge sub-modules in a single bridge arm in the M3C converter, C 0 Is the capacitance value L of an energy storage capacitor C in the M3C converter arm Is the inductance value L of the bridge arm inductance L1 in the M3C converter, L k The inductance value of the line inductance L2 in the low-frequency power transmission system.
Preferably, the three-phase output voltage peak value U of the M3C converter s And the angular frequency ω is sampled as follows:
obtaining a waveform of the three-phase output voltage of the M3C converter in a complete period T through sampling, and then taking a peak value U of the three-phase output voltage of the M3C converter as the maximum value in the waveform s The angular frequency ω is calculated from ω=2pi/T.
The invention also provides a low-frequency power transmission system which comprises a fan, a modularized multi-level matrix converter, three identical line inductances L2, three identical current-limiting resistors R and an alternating current power supply u s And recording the modularized multi-level matrix converter as an M3C converter, wherein the output end of the fan is connected with the input end of the M3C converter, and three phases of the output end of the M3C converter are respectively connected with a line inductor L2 and a current limiting resistor R in series and then connected into an alternating current power supply.
Preferably, the M3C converter includes three identical sub-converters, each sub-converter includes identical three-phase bridge arms, and an input end of each bridge arm is connected in series with a bridge arm inductance L1; each bridge arm comprises N identical and cascaded full-bridge submodules, and each full-bridge submodule comprises an energy storage capacitor C.
The invention also provides a fault current simplification analysis system of the low-frequency power transmission system, which comprises the following steps:
peak value U for sampling three-phase output voltage of M3C converter s A sampling module of angular frequency omega;
the control module is used for equating a fault loop in the evolution process of the fault current into a front charge RLC equivalent circuit, a discharge RLC equivalent circuit and a rear charge RLC equivalent circuit according to the state of the M3C converter when the fault occurs;
for according to peak value U s The angular frequency omega and the three RLC equivalent circuits establish three fault current analytic control modules;
for obtaining the fault current i of the pre-charge phase from three fault current resolution calculations f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 A calculation module of (a);
for fault current i in accordance with the pre-charge phase f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 Obtaining fault current i at any fault occurrence time t after fault f A calculation module of (a);
and a microprocessor and a memory, each of said modules, microprocessors being programmed or configured to perform the steps of the fault current reduction analysis method for a low frequency transmission system as claimed in any one of claims 1 to 6.
The present invention also provides a computer-readable storage medium having stored therein a computer program programmed or configured to perform the low frequency transmission system fault current simplification parsing method of any one of claims 1 to 6.
The invention provides a simplified analysis method and a simplified analysis system for fault current of a low-frequency power transmission system, which divide the evolution process of the fault current into three stages according to the behavior of an M3C converter after the fault occurs, and deduce the analysis method for the fault current by an RLC equivalent circuit of a fault loop of the three stages, wherein the simplified analysis method and the simplified analysis system for the fault current have the following advantages that:
1. the invention analyzes the fault current path and the change rule based on the mechanism of fault current generation, and obtains the RLC equivalent circuit of three stages after the system fault, which has simple structure, easy understanding and strong popularization value in the aspect of the fault analysis of the low-frequency power transmission system based on M3C.
2. According to the invention, the fault current can be rapidly analyzed and calculated by only acquiring the intrinsic parameters of the elements of the system and sampling the normal operation parameters, the change rule of the fault current along with time after the fault occurs can be accurately described without complex modeling and simulation work, and a reference basis is provided for relay protection setting calculation and electrical equipment selection verification.
Drawings
Fig. 1 is a topology diagram of a low frequency power transmission system according to the present invention.
Fig. 2 is a topology diagram of a pre-charge RLC equivalent circuit.
Fig. 3 is a topology diagram of a capacitive discharge RLC equivalent circuit.
Fig. 4 is a topology diagram of an ac short RLC equivalent circuit.
Fig. 5 is a topology diagram of a post-charge RLC equivalent circuit.
Fig. 6 is a diagram of a fault current analysis calculation verification result according to an embodiment of the present invention.
Fig. 7 is a graph of a total voltage analysis, calculation and verification result of a full-bridge submodule capacitor after a fault according to an embodiment of the present invention.
Fig. 8 is a topology of a full-bridge sub-module.
FIG. 9 is a flow chart of the parsing method of the present invention.
Detailed Description
Fig. 1 is a topology diagram of a low frequency power transmission system provided by the present invention. The low-frequency power transmission system comprises a fan, a modularized multi-level matrix converter, three identical line inductances L2, three identical current limiting resistors R and an alternating current power supply u s And recording the modularized multi-level matrix converter as an M3C converter, wherein the output end of the fan is connected with the input end of the M3C converter, and three phases of the output end of the M3C converter are respectively connected with a line inductor L2 and a current limiting resistor R in series and then connected into an alternating current power supply.
In the embodiment of the invention, the M3C converter comprises three identical sub converters, each sub converter comprises identical three-phase bridge arms, and the input end of each bridge arm is connected in series with a bridge arm inductance L1; each bridge arm comprises N identical and cascaded full-bridge submodules, and each full-bridge submodule comprises an energy storage capacitor C.
In fig. 1, three sub-converters are designated as an a sub-converter, a b sub-converter and a C sub-converter, respectively, and any one full-bridge sub-module of the M3C converter is designated as SM kij K is the phase sequence, k=a, b, c, i is the bridge arm sequence number, i=u, w, v, j is the sequence number of the full bridge sub-module, i=1, 2. A, b and c in the figure are three-phase output ends of equivalent fans and are respectively connected with input ends of three bridge arms in the corresponding sub-converters, and three SM of the three bridge arms in each sub-converter kin And after being connected in parallel, the corresponding phase output ends of the sub-converters are formed. In addition u in FIG. 1 a ，u b ，u c Is three phases of an alternating current power supply.
Fig. 8 is a topology diagram of a full-bridge submodule, and it can be seen from the diagram that the full-bridge submodule is composed of four switching tubes with antiparallel diodes and an energy storage capacitor C, wherein Q1, Q2, Q3 and Q4 are switching tubes, and D1, D2, D3 and D4 are diodes. The Quan Qiaozi module is composed of three parallel branches, namely, a first branch is formed by connecting Q1 and Q2 in series, and Q1 is in anti-parallel connection with D1 and Q2 is in anti-parallel connection with D2; the second branch is formed by connecting Q3 and Q4 in series, and Q3 is in anti-parallel connection with D3 and Q4 is in anti-parallel connection with D4; the third branch is an energy storage capacitor C.
The invention provides a fault current simplified analysis method of a low-frequency power transmission system, wherein the fault current is three-phase grounding fault current. Fig. 9 is a flowchart of the parsing method, and as can be seen from the figure, the simplified parsing method includes the following steps:
step 1, obtaining a peak value U of three-phase output voltage of an M3C converter through sampling s Angular frequency ω, s is the phase sequence, s=a, b, c. In an embodiment of the present invention, the three-phase output voltage peak value U of the M3C converter s And the angular frequency ω is sampled as follows: obtaining a waveform of the three-phase output voltage of the M3C converter in a complete period T through sampling, and then taking a peak value U of the three-phase output voltage of the M3C converter as the maximum value in the waveform s Calculated from ω=2pi/TAngular frequency omega.
Step 2, according to the state of the M3C converter when the fault occurs, the fault loop in the evolution process of the fault current is equivalent to a pre-charge RLC equivalent circuit, a discharge RLC equivalent circuit and a post-charge RLC equivalent circuit, and according to the peak value U s Three fault current analysis methods are established by the angular frequency omega and the three RLC equivalent circuits, and the fault current i of the pre-charging stage is calculated f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 。
Step 3, according to the fault current i of the previous charging stage f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 Obtaining fault current i at any fault occurrence time t after fault f 。
In the embodiment of the invention, the fault current i at any fault occurrence time t after the fault f The analytical formula of (2) is as follows:
wherein t is 0 For the starting time of the pre-charge phase, t 1 For the start time of the discharge phase, t 2 To start the post-charge phase, t 3 Is the end time of the post-charge phase.
Fault current i of the pre-charge phase f1 The solving process of (2) is as follows:
fig. 2 is a topology diagram of a pre-charge RLC equivalent circuit, which is an ac power supply u, as can be seen from fig. 2 s Current limiting resistor R, first equivalent capacitor C in low frequency power transmission system e And equivalent inductance L e A loop formed by the first equivalent capacitance C e Is connected with an alternating current power supply u s First equivalent capacitance C e Is connected with equivalent inductance L by negative electrode e Equivalent inductance L e The other end of the current limiting resistor R is connected with the alternating current power supply u s The current passing through the loop is the fault current i of the pre-charge stage f1 The method comprises the steps of carrying out a first treatment on the surface of the The resistance value of the current limiting resistor R is recorded as R eq ；
The fault current analysis of the pre-charging stage is as follows:
wherein, gamma 1 Additional phase of fault current for the pre-charge phase, Z 1 The impedance of the pre-charge RLC equivalent circuit is calculated by:
wherein C is eq For the first equivalent capacitance C e Capacitance value C of (C) eq ＝9C 0 /N，L eq Is equivalent to inductance L e Inductance value L of (1) eq ＝L arm /3+L k N is the number of full-bridge sub-modules in a single bridge arm in the M3C converter, C 0 Is the capacitance value L of an energy storage capacitor C in the M3C converter arm Is the inductance value L of the bridge arm inductance L1 in the M3C converter, L k The inductance value of the line inductance L2 in the low-frequency power transmission system.
Fault current i of the discharge phase f2 The solving process of (2) is as follows:
fault current i of the discharge phase f2 By capacitive discharge current i c And an alternating-current side short-circuit current i s The expression of the synthesized product is:
i f2 ＝i C +i s
the discharging RLC equivalent circuit comprises a capacitor discharging RLC equivalent circuit and an alternating current short circuit RLC equivalent circuit.
FIG. 3 is a topology of a capacitive discharge RLC equivalent circuit, which is one as can be seen from FIG. 3A current-limiting resistor R and a first equivalent capacitor C in the low-frequency power transmission system e And equivalent inductance L e A loop formed by the first equivalent capacitance C e Is connected with equivalent inductance L by positive electrode e Equivalent inductance L e The other end of the current limiting resistor R is connected with the first equivalent capacitor C e The current passing through the circuit is the capacitor discharge current i c The method comprises the steps of carrying out a first treatment on the surface of the The resistance value of the current limiting resistor R is recorded as R eq ；
Fig. 4 is a topology diagram of an ac short circuit RLC equivalent circuit, which is shown in fig. 4 as an ac power supply u s Current limiting resistor R and equivalent inductance L in low-frequency power transmission system e A loop formed by the same, wherein the equivalent inductance L e Is connected with an alternating current power supply u s . The other end of the current limiting resistor R is connected with the alternating current power supply u s The current passing through the loop is an alternating-current side short-circuit current i s 。
The fault current analysis of the discharging stage is as follows:
wherein C is eq For the first equivalent capacitance C e Capacitance value C of (C) eq ＝9C 0 N, N is the number of full-bridge sub-modules in a single bridge arm in the M3C converter, C 0 The capacitance value of the energy storage capacitor C in the M3C converter;
τ is a time constant, A is a constant coefficient, ω i Is the angular frequency of the capacitor discharge current, theta is the phase angle of the capacitor discharge current, gamma 2 For additional phase of short-circuit current at AC side, Z 2 The impedance of the circuit is the equivalent circuit of the AC short circuit RLC, and the calculation is respectively as follows:
τ＝2L eq /R eq
in U m Is the voltage at the energy storage capacitor C during the normal operation of the low-frequency power transmission system, I m Is the current at the energy storage capacitor C and L when the low-frequency power transmission system is in normal operation eq Is equivalent to inductance L e Inductance value L of (1) eq ＝L arm /3+L k ，L arm Is the inductance value L of the bridge arm inductance L1 in the M3C converter, L k The inductance value of the line inductance L2 in the low-frequency power transmission system.
Fault current i of the post-charge phase f3 The solving process of (2) is as follows:
fig. 5 is a topology diagram of a post-charge RLC equivalent circuit, which is an ac power supply u, as can be seen from fig. 5 s Current limiting resistor R, second equivalent capacitor C in low frequency power transmission system e ' and equivalent inductance L e A loop formed by the second equivalent capacitance C e ' the positive electrode is connected with an alternating current power supply u s Second equivalent capacitance C e Is connected with equivalent inductance L by negative electrode e Equivalent inductance L e The other end of the current limiting resistor R is connected with the power supply u s The current passing through the loop is the fault current i of the post-charging stage f3 The method comprises the steps of carrying out a first treatment on the surface of the The resistance value of the current limiting resistor R is recorded as R eq ；
The fault current analysis of the post-charging stage is as follows:
wherein, gamma 3 Additional phase of fault current for post-charge phase, Z 3 The impedance of the RLC equivalent circuit for post-charge is calculated by:
wherein C' eq Is the second equivalent capacitance C e Capacitance of 'C' eq ＝3C 0 /N，L eq Is equivalent to inductance L e Inductance value L of (1) eq ＝L arm /3+L k N is the number of full-bridge sub-modules in a single bridge arm in the M3C converter, C 0 Is the capacitance value L of an energy storage capacitor C in the M3C converter arm Is the inductance value L of the bridge arm inductance L1 in the M3C converter, L k The inductance value of the line inductance L2 in the low-frequency power transmission system.
In particular, based on the three-stage fault current analysis process, the total voltage of the full-bridge submodule capacitor in the three stages after the fault can be further solved and respectively recorded as the total voltage U of the full-bridge submodule capacitor in the front charging stage n Full bridge submodule capacitor total voltage U in discharging stage f2 Total voltage U of full-bridge submodule capacitor in post-charge phase f3 The calculation formula is as follows:
the invention also provides a fault current simplification analysis system of the low-frequency power transmission system, which comprises the following steps:
peak value U for sampling three-phase output voltage of M3C converter s A sampling module of angular frequency omega;
the control module is used for equating a fault loop in the evolution process of the fault current into a front charge RLC equivalent circuit, a discharge RLC equivalent circuit and a rear charge RLC equivalent circuit according to the state of the M3C converter when the fault occurs;
for according to peak value U s The angular frequency omega and the three RLC equivalent circuits establish three fault current analytic control modules;
for obtaining the fault current i of the pre-charge phase from three fault current resolution calculations f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 A calculation module of (a);
for fault current i in accordance with the pre-charge phase f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 Obtaining fault current i at any fault occurrence time t after fault f A calculation module of (a);
and a microprocessor and a memory, each of said modules, microprocessors being programmed or configured to perform the steps of the fault current reduction analysis method for a low frequency transmission system as claimed in any one of claims 1 to 6.
The present invention also provides a computer-readable storage medium having stored therein a computer program programmed or configured to perform the low frequency transmission system fault current simplification parsing method of any one of claims 1 to 6.
Simulations were performed in order to verify the effect of the present invention. The PSCAD electromagnetic simulation platform is used for constructing a simulation model of the low-frequency power transmission system based on the system parameters of the table 1, and a three-phase ground fault case is set for testing the analysis method.
Table 1 low frequency power transmission system parameters
The simulation and analysis calculation result pairs of the embodiment of the invention are shown in fig. 6 and fig. 7. It can be seen that the input storage capacitor is in a charged and discharged state before the M3C converter is locked. And in the charging process, the bridge arm equivalent capacitance is larger, so that the overcurrent problem can not occur. The bridge arm fault current in the discharging process consists of a capacitor discharging current and an alternating current short circuit current, wherein the capacitor discharging current is the main part of bridge arm overcurrent. After the converter is locked, the energy storage capacitors of all the full-bridge submodules form a charging loop through anti-parallel diodes, and the energy stored by the loop inductance and the energy supply of an alternating current system can cause the energy storage capacitors of the full-bridge submodules to have overvoltage problems.
The analytical calculation curve is basically consistent with the simulation curve, so that the accuracy of the analytical formula is verified. The analysis calculation curve and the simulation curve have larger deviation in the charge and discharge process before locking, and the main reason is that the calculation model ignores the process of switching real-time change of the bridge arm submodules and ignores factors such as reactance resistance of the bridge arm, on-state resistance of the power electronic device and the like.
In summary, the fault current simplified analysis method and system for the low-frequency power transmission system provided by the invention have the advantages that the fault current analysis method is deduced by the RLC equivalent circuit of the three-stage fault loop, complex modeling simulation is avoided, the fault current can be rapidly analyzed and calculated according to the element inherent parameters and the normal operation parameters of the system, and the applicability and popularization value are relatively high.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The scheme in the embodiment of the invention can be realized by adopting various computer languages, such as object-oriented programming language Java, an transliteration script language JavaScript and the like.
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.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims (8)

1. The simplified analysis method for the fault current of the low-frequency power transmission system is characterized by comprising the following steps of:
obtaining peak value U of three-phase output voltage of M3C converter by sampling s Angular frequency ω, s is phase sequence, s=a, b, c;
according to the state of the M3C converter when the fault occurs, the fault loop in the evolution process of the fault current is equivalent to a pre-charge RLC equivalent circuit, a discharge RLC equivalent circuit and a post-charge RLC equivalent circuit, and according to the peak value U s Three fault current analysis methods are established by the angular frequency omega and the three RLC equivalent circuits, and the fault current i of the pre-charging stage is calculated f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 ；
According to the fault current i of the pre-charge phase f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 Obtaining fault current i at any fault occurrence time t after fault f 。
2. The simplified analysis method of fault current of low frequency power transmission system according to claim 1, wherein the fault current i at any fault occurrence time t after the fault f The analytical formula of (2) is as follows:
wherein t is 0 For the starting time of the pre-charge phase, t 1 For the start time of the discharge phase, t 2 To start the post-charge phase, t 3 Is the end time of the post-charge phase.
3. The simplified analysis method of fault current of low frequency power transmission system according to claim 1, wherein the fault current i of the pre-charging stage f1 The solving process of (2) is as follows:
the pre-charging RLC equivalent circuit is an alternating current power supply u s Current limiting resistor R, first equivalent capacitor C in low frequency power transmission system e And equivalent inductance L e A loop formed by the first equivalent capacitance C e Is connected with an alternating current power supply u s First equivalent capacitance C e Is connected with equivalent inductance L by negative electrode e Equivalent inductance L e The other end of the current limiting resistor R is connected with the alternating current power supply u s The current passing through the loop is the fault current i of the pre-charge stage f1 The method comprises the steps of carrying out a first treatment on the surface of the The resistance value of the current limiting resistor R is recorded as R eq ；
The fault current analysis of the pre-charging stage is as follows:
wherein, gamma 1 Additional phase of fault current for the pre-charge phase, Z 1 The impedance of the pre-charge RLC equivalent circuit is calculated by:
wherein C is eq For the first equivalent capacitance C e Capacitance value C of (C) eq ＝9C 0 /N，L eq Is equivalent to inductance L e Inductance value L of (1) eq ＝L arm /3+L k N is the number of full-bridge sub-modules in a single bridge arm in the M3C converter, C 0 Is the capacitance value L of an energy storage capacitor C in the M3C converter arm Is the inductance value L of the bridge arm inductance L1 in the M3C converter, L k The inductance value of the line inductance L2 in the low-frequency power transmission system.
4. The simplified analysis method of fault current of low frequency power transmission system according to claim 1, wherein the fault current i of the discharging phase f2 The solving process of (2) is as follows:
fault current i of the discharge phase f2 By capacitive discharge current i c And an alternating-current side short-circuit current i s The expression of the synthesized product is:
i f2 ＝i C +i s
the discharging RLC equivalent circuit comprises a capacitor discharging RLC equivalent circuit and an alternating current short circuit RLC equivalent circuit;
the capacitor discharging RLC equivalent circuit is composed of a current-limiting resistor R and a first equivalent capacitor C in a low-frequency power transmission system e And equivalent inductance L e A loop formed by the first equivalent capacitance C e Is connected with equivalent inductance L by positive electrode e Equivalent inductance L e The other end of the current limiting resistor R is connected with the first equivalent capacitor C e The current passing through the circuit is the capacitor discharge current i C The method comprises the steps of carrying out a first treatment on the surface of the The resistance value of the current limiting resistor R is recorded as R eq ；
The AC short circuit RLC equivalent circuit is an AC power supply u s Current limiting resistor R and equivalent inductance L in low-frequency power transmission system e A loop formed by the same, wherein the equivalent inductance L e Is connected with an alternating current power supply u s The other end of the current limiting resistor R is connected with the alternating current power supply u s The current passing through the loop is an alternating-current side short-circuit current i s ；
The fault current analysis of the discharging stage is as follows:
wherein C is eq For the first equivalent capacitance C e Capacitance value C of (C) eq ＝9C 0 N, N is the number of full-bridge sub-modules in a single bridge arm in the M3C converter, C 0 The capacitance value of the energy storage capacitor C in the M3C converter;
τ is a time constant, A is a constant coefficient, ω i Is the angular frequency of the capacitor discharge current, theta is the phase angle of the capacitor discharge current, gamma 2 For additional phase of short-circuit current at AC side, Z 2 The impedance of the circuit is the equivalent circuit of the AC short circuit RLC, and the calculation is respectively as follows:
τ＝2L eq /R eq
in U m Is the voltage at the energy storage capacitor C during the normal operation of the low-frequency power transmission system, I m Is the current at the energy storage capacitor C and L when the low-frequency power transmission system is in normal operation eq Is equivalent to inductance L e Inductance value L of (1) eq ＝L arm /3+L k ，L arm Is the inductance value L of the bridge arm inductance L1 in the M3C converter, L k The inductance value of the line inductance L2 in the low-frequency power transmission system.
5. The simplified analysis method of fault current of low frequency power transmission system according to claim 1, wherein the fault current i of the post-charging stage f3 The solving process of (2) is as follows:
the back charging RLC equivalent circuit is an AC power supply u s Current limiting resistor R, second equivalent capacitor C in low frequency power transmission system e ' and equivalent inductance L e A loop formed by the second equivalent capacitance C e ' the positive electrode is connected with an alternating current power supply u s Second equivalent capacitance C e ' negative electrode connected equivalent inductance L e Equivalent inductance L e The other end of the current limiting resistor R is connected with the power supply u s The current passing through the loop is the fault current i of the post-charging stage f3 The method comprises the steps of carrying out a first treatment on the surface of the The resistance value of the current limiting resistor R is recorded as R eq ；
The fault current analysis of the post-charging stage is as follows:
wherein, gamma 3 Additional phase of fault current for post-charge phase, Z 3 The impedance of the RLC equivalent circuit for post-charge is calculated by:
wherein C' eq Is the second equivalent capacitance C e Capacitance of 'C' eq ＝3C 0 /N，L eq Is equivalent to inductance L e Inductance value L of (1) eq ＝L arm /3+L k N is the number of full-bridge sub-modules in a single bridge arm in the M3C converter, C 0 Is the capacitance value L of an energy storage capacitor C in the M3C converter arm Is the inductance value L of the bridge arm inductance L1 in the M3C converter, L k The inductance value of the line inductance L2 in the low-frequency power transmission system.
6. The simplified fault current analysis method of a low frequency power transmission system according to claim 1, wherein the peak value U of the three-phase output voltage of the M3C converter s And the angular frequency ω is sampled as follows:
obtaining a waveform of the three-phase output voltage of the M3C converter in a complete period T through sampling, and then taking a peak value U of the three-phase output voltage of the M3C converter as the maximum value in the waveform s The angular frequency ω is calculated from ω=2pi/T.
7. A simplified fault current analysis system for a low frequency power transmission system, comprising:
peak value U for sampling three-phase output voltage of M3C converter s A sampling module of angular frequency omega;
the control module is used for equating a fault loop in the evolution process of the fault current into a front charge RLC equivalent circuit, a discharge RLC equivalent circuit and a rear charge RLC equivalent circuit according to the state of the M3C converter when the fault occurs;
for according to peak value U s The angular frequency omega and the three RLC equivalent circuits establish three fault current analytic control modules;
for obtaining the fault current i of the pre-charge phase from three fault current resolution calculations f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 A calculation module of (a);
for fault current i in accordance with the pre-charge phase f1 Fault current i during discharge phase f2 And fault current i in the post-charge phase f3 Obtaining fault current i at any fault occurrence time t after fault f A calculation module of (a);
and a microprocessor and a memory, each of said modules, microprocessors being programmed or configured to perform the steps of the fault current reduction analysis method for a low frequency transmission system as claimed in any one of claims 1 to 6.
8. A computer-readable storage medium, wherein a computer program programmed or configured to execute the low-frequency transmission system fault current simplification parsing method according to any one of claims 1 to 6 is stored in the computer-readable storage medium.
CN202211437213.1A 2022-11-15 2022-11-15 Simplified analysis method and system for fault current of low-frequency power transmission system Active CN116148589B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202211437213.1A CN116148589B (en) 2022-11-15 2022-11-15 Simplified analysis method and system for fault current of low-frequency power transmission system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202211437213.1A CN116148589B (en) 2022-11-15 2022-11-15 Simplified analysis method and system for fault current of low-frequency power transmission system

Publications (2)

Publication Number Publication Date
CN116148589A CN116148589A (en) 2023-05-23
CN116148589B true CN116148589B (en) 2023-09-19

Family

ID=86349671

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202211437213.1A Active CN116148589B (en) 2022-11-15 2022-11-15 Simplified analysis method and system for fault current of low-frequency power transmission system

Country Status (1)

Country Link
CN (1) CN116148589B (en)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114034971A (en) * 2021-10-27 2022-02-11 华南理工大学 Method, system, device and medium for processing line fault in low-frequency power transmission system
CN114156933A (en) * 2021-12-03 2022-03-08 西安端怡科技有限公司 Method for coping after MMMC bridge arm fault
CN114200213A (en) * 2021-11-01 2022-03-18 国网浙江省电力有限公司杭州供电公司 Capacitance online monitoring method and device of low-frequency power transmission matrix converter
CN114329980A (en) * 2021-12-30 2022-04-12 国网浙江省电力有限公司电力科学研究院 Electromechanical transient modeling method and topological structure of modular multilevel matrix converter
CN114696359A (en) * 2022-04-08 2022-07-01 国网浙江省电力有限公司电力科学研究院 Fault-tolerant operation method and device for low-frequency power transmission system
CN114784845A (en) * 2021-11-09 2022-07-22 国电南瑞科技股份有限公司 M3C low-frequency converter and fault ride-through method and system thereof
CN115149567A (en) * 2022-05-11 2022-10-04 国网浙江省电力有限公司 M3C-based data-driven model-free control method for low-frequency power transmission system

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114034971A (en) * 2021-10-27 2022-02-11 华南理工大学 Method, system, device and medium for processing line fault in low-frequency power transmission system
CN114200213A (en) * 2021-11-01 2022-03-18 国网浙江省电力有限公司杭州供电公司 Capacitance online monitoring method and device of low-frequency power transmission matrix converter
CN114784845A (en) * 2021-11-09 2022-07-22 国电南瑞科技股份有限公司 M3C low-frequency converter and fault ride-through method and system thereof
CN114156933A (en) * 2021-12-03 2022-03-08 西安端怡科技有限公司 Method for coping after MMMC bridge arm fault
CN114329980A (en) * 2021-12-30 2022-04-12 国网浙江省电力有限公司电力科学研究院 Electromechanical transient modeling method and topological structure of modular multilevel matrix converter
CN114696359A (en) * 2022-04-08 2022-07-01 国网浙江省电力有限公司电力科学研究院 Fault-tolerant operation method and device for low-frequency power transmission system
CN115149567A (en) * 2022-05-11 2022-10-04 国网浙江省电力有限公司 M3C-based data-driven model-free control method for low-frequency power transmission system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
柔性低频输电高频谐振风险评估及抑制方法研究;华文 等;浙江电力;第41卷(第10期);全文 *

Also Published As

Publication number Publication date
CN116148589A (en) 2023-05-23

Similar Documents

Publication Publication Date Title
Li et al. A pole-to-pole short-circuit fault current calculation method for DC grids
Herman et al. A proportional-resonant current controller for selective harmonic compensation in a hybrid active power filter
Saad et al. Real time simulation of MMCs using the state-space nodal approach
CN108229021B (en) Blocking modeling method of modular multilevel converter based on real-time digital simulator
CN110190618B (en) Flexible direct current converter station model equivalent method under alternating current fault ride-through working condition
Strezoski et al. Sequence domain calculation of active unbalanced distribution systems affected by complex short circuits
CN106407494A (en) Bipolar short circuit fault current calculation method of MMC-based HVDC system
Freijedo et al. Harmonic resonances in wind power plants: modeling, analysis and active mitigation methods
Li et al. Modeling and control of a full-bridge modular multilevel STATCOM
CN111654052A (en) Flexible direct current converter modeling device and method based on dynamic phasor method
CN106787890A (en) A kind of CDSM MMC bridge arms electromagnetic transient modeling method and apparatus
CN115563921A (en) Method and system for determining fault transient electric quantity of flexible direct current transmission line
Irnawan et al. Evaluation of half-bridge modular multilevel converter model for VSC-HVDC transient stability studies
CN109600064B (en) Method and system for calculating alternating current asymmetric fault main loop of modular multilevel converter
Tremblay et al. Real-time simulation of a fully detailed type-IV wind turbine
CN116613961B (en) Mixed MMC simulation model and method for simulating locking state of bridge arm
CN116148589B (en) Simplified analysis method and system for fault current of low-frequency power transmission system
CN108376992B (en) MMC equivalent simulation method for hybrid sub-module
CN110048427A (en) A kind of multiterminal flexible direct current distribution power flow protection fixed value calculation method
Li Real-time simulation of CDSM modular multilevel converter for HIL test applications
Galarza Software and processor-in-the-loop execution for a grid connected modular multi-level converter
CN108365631B (en) Reactive voltage control circuit simulation method and system of distributed grid-connected converter
CN111769562A (en) Virtual impedance-based power quality frequency division control method and system
Arunprasanth et al. A generic point-to-point mmc-vsc system for real-time and off-line simulation studies
Ahmed et al. A comprehensive modeling of double tuned filter for efficient mitigation of harmonic distortion

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant