CN114696359A - Fault-tolerant operation method and device for low-frequency power transmission system - Google Patents

Fault-tolerant operation method and device for low-frequency power transmission system Download PDF

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CN114696359A
CN114696359A CN202210369374.5A CN202210369374A CN114696359A CN 114696359 A CN114696359 A CN 114696359A CN 202210369374 A CN202210369374 A CN 202210369374A CN 114696359 A CN114696359 A CN 114696359A
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bridge
low
fault
frequency
bridge arm
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许烽
金玉琪
黄晓明
胡俊华
陈晓刚
徐华
潘武略
陆承宇
陆翌
裘鹏
张健
毛航银
倪晓军
林进钿
陈骞
丁超
郑眉
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State Grid Zhejiang Electric Power Co Ltd
Electric Power Research Institute of State Grid Zhejiang Electric Power Co Ltd
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State Grid Zhejiang Electric Power Co Ltd
Electric Power Research Institute of State Grid Zhejiang Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases

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  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention discloses a fault-tolerant operation method and device for a low-frequency power transmission system. The technical scheme adopted by the invention is as follows: if a full-bridge submodule fails in the bridge arm, the failed full-bridge submodule only needs to be bypassed as long as the number of the failed full-bridge submodule does not exceed the number of the redundant submodules; if the number of the fault sub-modules in the bridge arm exceeds the redundancy number or a certain bridge arm of M3C cannot continuously and normally operate due to other fault reasons, switching the M3C from the nine-bridge-arm operation state to the six-bridge-arm operation state on line; for a two-terminal low-frequency power transmission system, when a low-frequency power transmission line has a single-phase permanent fault, a single-phase line is isolated, the low-frequency side of M3C is changed from three-phase operation to two-phase operation, and the low-frequency power transmission system continuously keeps an operation state. The invention can realize that the low-frequency power transmission system still has all or partial power transmission capability under module faults, bridge arm faults and line faults, and can effectively improve the operation reliability of the low-frequency power transmission system.

Description

Fault-tolerant operation method and device for low-frequency power transmission system
Technical Field
The invention belongs to the field of power transmission of power systems, and particularly relates to a fault-tolerant operation method and device of a low-frequency power transmission system.
Background
The low-frequency power transmission is beneficial to supplement of a power frequency alternating current power transmission mode and a direct current power transmission mode by reducing the power transmission frequency, reducing the line impedance, reducing the cable charging reactive power and improving the transmission capacity and the regulation and control capacity of a power grid, and is suitable for scenes of medium-distance and long-distance offshore wind power transmission, urban power grid partition interconnection, island interconnection power supply and the like. The core for realizing the low-frequency transmission system is an AC-AC frequency converter, and through years of research, the low-frequency transmission system is developed to a third generation AC-AC frequency converter-a modular multilevel matrix converter (M3C) from a frequency doubling transformer and a cycle frequency converter at present. M3C contains nine legs, each leg containing one leg reactance and multiple cascaded full-bridge submodules.
For low-frequency engineering, the operational reliability is a very critical data, but the influence of equipment failure, external disturbance and the like is inevitable. Under the current condition of engineering, how to improve the operation reliability of the low-frequency power transmission engineering, namely the fault-tolerant operation capability, without increasing the investment as much as possible is very important and has significant meaning.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a fault-tolerant operation method and device for a low-frequency power transmission system based on M3C, which starts from three layers of a module level, a device level and a system level, and realizes that the low-frequency power transmission system still has all or part of power transmission capability under module faults, bridge arm faults and line faults only through control logic optimization under the condition of utilizing the existing primary equipment framework.
Therefore, the invention adopts a technical scheme that: a fault-tolerant operation method of a low-frequency power transmission system comprises an exchange frequency station and a low-frequency power transmission network, wherein the exchange frequency station is more than two ends, the exchange frequency station adopts M3C, M3C comprises 9 bridge arms, each bridge arm comprises a bridge arm reactance and a plurality of cascaded full-bridge submodules, and the method comprises the following steps:
1) if a full-bridge submodule fails in a bridge arm, as long as the number of the failed full-bridge submodule does not exceed the number of the redundant submodules, the failed full-bridge submodule only needs to be operated by a bypass, the exchange frequency station can still normally operate, the power transmission capability is not influenced, and the bridge arm has certain fault-tolerant operation capability due to the existence of the redundant submodules;
2) if the number of the fault sub-modules in the bridge arm exceeds the redundancy number or a certain bridge arm of M3C cannot continuously and normally run due to other fault reasons, the M3C is switched from the nine-bridge-arm running state to the six-bridge-arm running state on line, the low-frequency power transmission system can still keep the running state, but the transmission power is reduced to some extent;
3) for a two-terminal low-frequency power transmission system, when a low-frequency power transmission line has a single-phase permanent fault, a single-phase line is isolated, the low-frequency side of M3C is changed from three-phase operation to two-phase operation, and the low-frequency power transmission system continues to keep the operation state, but the transmission power is reduced to some extent.
The invention mainly aims at line fault tolerance of M3C and a two-end type low-frequency power transmission system, and relates to a module level, a device level and a system level.
Further, in 1), it is assumed that each bridge arm includes N full-bridge submodules, where Nm is the number of rated full-bridge submodules, Nr is the number of redundant full-bridge submodules, and N is Nm + Nr, when the total number of full-bridge submodules with a fault in the bridge arm is less than or equal to Nr, the operation of the ac-ac frequency station is not affected, the bypass switch of the full-bridge submodule with the fault is in a closed state, and the full-bridge submodule is in a bypass state.
Further, in 2), the bridge arm selection method for switching the nine bridge arms into the six bridge arms is as follows: assuming that x (a, b, c) represents three phases of the power frequency and y (u, v, w) represents three phases of the low frequency, nine bridge arms are identified by xy; if the bridge arm withdrawn due to fault is x0y0Then select and x again0And y0Two irrelevant bridge arms are withdrawn, and the withdrawn bridge arm identifications are not the same in x and y.
Further, in the step 2), after the nine-leg bridge is switched to the six-leg bridge for operation, the operation is restricted by the formula (1), wherein Q issIs reactive power, Q, of the M3C power frequency sidelIs reactive power, V, of the low frequency side of M3CNOIs a neutral point of low frequency system, IcirIs a six-arm M3C circulating current, as shown in formula (2), wherein k is 1,2, …,6, ibkIs the bridge arm current;
Figure BDA0003587395190000021
Figure BDA0003587395190000022
after the six-bridge arm is switched to, V is required to be met in order to ensure that the six-bridge arm M3C normally operatesNOWhen Q is equal to 0, Q is controlledsAnd QlEqual to zero, or QsAnd QlThe direction is opposite.
Further, in the step 3), after the single-phase line is isolated due to a permanent fault, the sub frequency conversion valve connected with the fault is locked, two sub frequency conversion valves connected with the other two phases continue to operate, and the low-frequency side outputs the low-frequency voltage with the phase angle difference of 180 degrees.
Furthermore, the sub-frequency conversion valve is composed of three bridge arms connected with a power frequency three-phase and a low frequency one-phase, and is similar to a STATCOM converter valve structure when viewed from a power frequency side.
The other technical scheme adopted by the invention is as follows: a fault tolerant operation device for a low frequency power transmission system, comprising:
a module failure unit: if a full-bridge submodule fails in a bridge arm, as long as the number of the failed full-bridge submodules does not exceed the number of the redundant submodules, the failed full-bridge submodule only needs to perform bypass operation, the exchange frequency station can still normally operate, the power transmission capability is not influenced, and the bridge arm has certain fault-tolerant operation capability due to the existence of the redundant submodules;
a bridge arm fault unit: if the number of the fault sub-modules in the bridge arm exceeds the redundancy number or one bridge arm of the M3C cannot continuously and normally run due to other fault reasons, the M3C is switched from the nine-bridge-arm running state to the six-bridge-arm running state on line, the low-frequency power transmission system can still keep the running state, but the transmission power is reduced to some extent;
a line fault unit: for a two-terminal low-frequency power transmission system, when a low-frequency power transmission line has a single-phase permanent fault, a single-phase line is isolated, the low-frequency side of M3C is changed from three-phase operation to two-phase operation, and the low-frequency power transmission system continues to keep the operation state, but the transmission power is reduced to some extent.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention can realize that the low-frequency power transmission system still maintains all or part of power transmission capability under module faults, bridge arm faults and line faults, and can effectively improve the operation reliability of the low-frequency power transmission system under the condition of not increasing equipment investment.
Drawings
FIG. 1 is a schematic diagram of a low frequency power transmission system of the present invention;
FIG. 2 is a schematic diagram of a fault tolerant method of operation of a low frequency power transmission system according to the present invention;
FIG. 3 is a schematic view of a M3C sub-converter valve of the present invention;
fig. 4 is a schematic structural diagram of the fault-tolerant operation device of the low-frequency power transmission system.
Detailed Description
To describe the present invention more specifically, the following detailed description of the technical solution of the present invention and the related principles thereof are provided with reference to the accompanying drawings and the detailed description.
Example 1
The embodiment is a fault-tolerant operation method of a low-frequency power transmission system. Fig. 1 is a schematic diagram of a three-terminal low frequency power transmission system, which, as can be seen, includes a three-terminal ac switching station and a low frequency power transmission network. The main equipment of the AC-AC frequency-switching station from the power frequency side to the low frequency side is provided with a connecting transformer, a starting resistor, a modular multilevel matrix converter (M3C) and the like in sequence. M3C contains 9 legs, each leg containing one leg reactance and multiple cascaded full bridge submodules.
The fault-tolerant operation method of the low-frequency power transmission system mainly aims at line faults of M3C and a two-end type low-frequency power transmission system, and relates to a module level, a device level and a system level, as shown in FIG. 2, the specific conditions are as follows:
(1) if a full-bridge submodule fails in a bridge arm, the exchange frequency station can still normally operate as long as the number of the full-bridge submodules with the failures does not exceed the number of the redundant submodules, and the power transmission capability is not affected. The failed full-bridge sub-module only needs to be bypassed. The existence of the redundant sub-modules enables the bridge arm to have certain fault-tolerant operation capability.
In this case, it is assumed that each bridge arm includes N full-bridge submodules, where Nm is the number of rated full-bridge submodules, Nr is the number of redundant full-bridge submodules, and N is Nm + Nr. When the total number of the full-bridge submodules with faults in the bridge arm is less than or equal to Nr, the operation of the alternating-current frequency-converting station is not influenced, the bypass switch of the full-bridge submodule with the faults is in a closed state, and the full-bridge submodule is in a bypass state.
(2) If the number of the fault sub-modules in the bridge arm exceeds the redundancy number or a certain bridge arm of the M3C cannot continuously and normally operate due to other reasons such as faults and the like, the M3C is switched from the nine-bridge-arm operation state to the six-bridge-arm operation state on line, the low-frequency power transmission system can still keep the operation state, but the power is reduced to some extent.
In this case, the bridge arm selection method for switching the nine bridge arms to the six bridge arms is as follows: assuming that x (a, b, c) represents the three phases of the power frequency and y (u, v, w) represents the three phases of the low frequency, nine arms can be identified by xy. If the bridge arm withdrawn due to fault is x0y0Then select and x again0And y0Two irrelevant bridge arms are withdrawn, and the withdrawn bridge arm identifications are not the same in x and y. For example, if the bw bridge arm needs to exit due to a fault, two normal bridge arms which can select two combination modes of au, cv or av and cu exit together, and M3C is switched from the nine-bridge arm state to the six-bridge arm state.
After the nine bridge arms are switched into the six bridge arms to operate, the operation is restricted by a formula (1), wherein QsIs reactive power, Q, of the M3C power frequency sidelIs reactive power, V, at the low frequency side of M3CNOIs a neutral point of low frequency system, IcirIs a six-arm M3C loop, as shown in formula (2), wherein k is 1,2, …,6, ibkIs the bridge arm current.
Figure BDA0003587395190000051
Figure BDA0003587395190000052
After the six-bridge arm is switched to, V is required to be met in order to ensure that the six-bridge arm M3C normally operatesNOWhen Q is equal to 0, Q is controlledsAnd QlEqual to zero, or QsAnd QlThe direction is opposite. Since the number of arms is reduced by 1/3, the power transmission capability of the six-arm M3C is 2/3 of the nine-arm M3C.
(3) For a two-terminal low-frequency power transmission system, when a low-frequency power transmission line has a single-phase permanent fault, a single-phase line is isolated, the low-frequency side of M3C is changed from three-phase operation to two-phase operation, and the low-frequency power transmission system continues to keep the operation state, but the transmission power is reduced to some extent.
In this case, after the single-phase line is isolated due to a permanent fault, the sub frequency conversion valve connected with the fault phase is locked, the two sub frequency conversion valves connected with the other two phases continue to operate, and the low-frequency side outputs the low-frequency voltage with the phase angle difference of 180 degrees. At transmission capacity, the low frequency power transmission system for two phase operation is 2/3 for three phase operation. The sub-frequency conversion valve is composed of three bridge arms connected with a power frequency three-phase and a low frequency one-phase, and is similar to a STATCOM converter valve structure when viewed from a power frequency side.
Example 2
The embodiment is a fault-tolerant operation device of a low-frequency power transmission system, and is composed of a module fault unit, a bridge arm fault unit and a line fault unit, as shown in fig. 4.
Module failure unit: if a full-bridge submodule fails in a bridge arm, the exchange frequency station can still normally operate as long as the number of the failed full-bridge submodules does not exceed the number of the redundant submodules, the power transmission capability is not affected, and the failed full-bridge submodule only needs to be bypassed.
A bridge arm fault unit: if the number of the fault sub-modules in the bridge arm exceeds the redundancy number or a certain bridge arm of the M3C cannot continuously and normally operate due to other fault reasons, the M3C is switched from the nine-bridge-arm operation state to the six-bridge-arm operation state on line, and the low-frequency power transmission system can still keep the operation state.
A line fault unit: for a two-end type low-frequency power transmission system, when a low-frequency power transmission line has a single-phase permanent fault, a single-phase line is isolated, the low-frequency side of the M3C is changed from three-phase operation to two-phase operation, and the low-frequency power transmission system continuously keeps an operation state.
In the module fault unit, each bridge arm is assumed to contain N full-bridge submodules, wherein Nm is the number of rated full-bridge submodules, Nr is the number of redundant full-bridge submodules, and N is Nm + Nr.
In the bridge arm fault unit, the bridge arm selection method for switching the nine bridge arms into the six bridge arms is as follows: assuming that x (a, b, c) represents three phases of the power frequency and y (u, v, w) represents three phases of the low frequency, nine bridge arms are identified by xy; if the bridge arm withdrawn due to fault is x0y0Then select and x again0And y0Two irrelevant bridge arms are withdrawn, and the withdrawn bridge arm identifications are not the same in x and y.
In the bridge arm fault unit, after the nine bridge arms are switched into the six bridge arms to operate, the operation is restricted by a formula (1), wherein QsIs reactive power, Q, of the M3C power frequency sidelIs reactive power, V, at the low frequency side of M3CNOIs a neutral point of low frequency system, IcirIs a six-arm M3C circulating current, as shown in formula (2), wherein k is 1,2, …,6, ibkIs the bridge arm current;
Figure BDA0003587395190000061
Figure BDA0003587395190000062
after the six-bridge arm is switched to, V is required to be met in order to ensure that the six-bridge arm M3C normally operatesNOWhen Q is equal to 0, Q is controlledsAnd QlEqual to zero, or QsAnd QlThe direction is opposite.
In the line fault unit, after a single-phase line is isolated due to a permanent fault, the sub frequency conversion valve connected with the fault is locked, two sub frequency conversion valves connected with other two phases continue to operate, and the low-frequency side outputs low-frequency voltage with phase angle difference of 180 degrees. At transmission capacity, the low frequency power transmission system for two phase operation is 2/3 for three phase operation. The sub-frequency conversion valve is composed of three bridge arms connected with a power frequency three-phase and a low frequency one-phase, and is similar to a STATCOM converter valve structure when viewed from a power frequency side.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (10)

1. A fault-tolerant operation method of a low-frequency power transmission system comprises an exchange frequency station and a low-frequency power transmission network, wherein the exchange frequency station adopts M3C, M3C comprises 9 bridge arms, each bridge arm comprises a bridge arm reactance and a plurality of cascaded full-bridge submodules, the fault-tolerant operation method is characterized in that,
1) if a full-bridge submodule fails in the bridge arm, the failed full-bridge submodule only needs to be bypassed as long as the number of the failed full-bridge submodule does not exceed the number of the redundant submodules;
2) if the number of the fault sub-modules in the bridge arm exceeds the redundancy number or a certain bridge arm of M3C cannot continuously and normally operate due to other fault reasons, switching the M3C from the nine-bridge-arm operation state to the six-bridge-arm operation state on line;
3) for a two-terminal low-frequency power transmission system, when a low-frequency power transmission line has a single-phase permanent fault, a single-phase line is isolated, the low-frequency side of M3C is changed from three-phase operation to two-phase operation, and the low-frequency power transmission system continuously keeps an operation state.
2. The fault-tolerant operation method of a low-frequency power transmission system according to claim 1, wherein in 1), each bridge arm is assumed to include N full-bridge submodules, where Nm is a rated number of full-bridge submodules, Nr is a redundant number of full-bridge submodules, and N is Nm + Nr.
3. The fault-tolerant operation method of the low-frequency power transmission system according to claim 1, wherein in 2), the bridge arm selection method for switching a nine-bridge arm into a six-bridge arm is as follows: assuming that x (a, b, c) represents three phases of the power frequency and y (u, v, w) represents three phases of the low frequency, nine bridge arms are identified by xy; if the bridge arm withdrawn due to fault is x0y0Then select and x again0And y0Two irrelevant bridge arms are withdrawn, and the withdrawn bridge arm identifications are not the same in x and y.
4. The fault-tolerant operation method of the low-frequency power transmission system according to claim 1, wherein in the step 2), after the nine-leg is switched to the six-leg to operate, the operation is restricted by a formula (1), wherein Q issIs reactive power, Q, of the M3C power frequency sidelIs reactive power, V, at the low frequency side of M3CNOIs a neutral point of low frequency system, IcirIs a six-arm M3C circulating current, as shown in formula (2), wherein k is 1,2, …,6, ibkIs the bridge arm current;
Figure FDA0003587395180000011
Figure FDA0003587395180000021
after the six-bridge arm is switched to, in order to ensure the normal operation of the six-bridge arm M3CNeed to satisfy VNOWhen Q is equal to 0, Q is controlledsAnd QlEqual to zero, or QsAnd QlThe direction is opposite.
5. The fault-tolerant operation method of the low-frequency power transmission system according to claim 1, wherein in the step 3), after the single-phase line is isolated due to the permanent fault, the sub frequency conversion valve connected with the fault is locked, while the two sub frequency conversion valves connected with the other two phases continue to operate, and the low-frequency side outputs the low-frequency voltage with the phase angle difference of 180 degrees.
6. The utility model provides a fault-tolerant running device of low frequency transmission system, low frequency transmission system include exchange frequency station and low frequency transmission network more than the both ends, exchange frequency station adopts M3C, M3C contains 9 bridge arms, and each bridge arm contains a bridge arm reactance and a plurality of cascade full-bridge submodule pieces, its characterized in that includes:
module failure unit: if a full-bridge submodule fails in the bridge arm, the failed full-bridge submodule only needs to be bypassed as long as the number of the failed full-bridge submodule does not exceed the number of the redundant submodules;
a bridge arm fault unit: if the number of the fault sub-modules in the bridge arm exceeds the redundancy number or a certain bridge arm of M3C cannot continuously and normally operate due to other fault reasons, switching the M3C from the nine-bridge-arm operation state to the six-bridge-arm operation state on line;
a line fault unit: for a two-terminal low-frequency power transmission system, when a low-frequency power transmission line has a single-phase permanent fault, a single-phase line is isolated, the low-frequency side of M3C is changed from three-phase operation to two-phase operation, and the low-frequency power transmission system continuously keeps an operation state.
7. The fault-tolerant operation device of a low-frequency power transmission system according to claim 6, wherein in the module fault unit, each bridge arm is assumed to have N full-bridge submodules, where Nm is the number of rated full-bridge submodules, Nr is the number of redundant full-bridge submodules, and N is Nm + Nr, when the total number of full-bridge submodules with faults in the bridge arm is less than or equal to Nr, the operation of the interchange frequency station is not affected, the bypass switch of the full-bridge submodule with faults is in a closed state, and the full-bridge submodule is in a bypass state.
8. The fault-tolerant operation device of a low-frequency power transmission system according to claim 6, wherein in the bridge arm fault unit, a bridge arm selection method for switching a nine bridge arm into a six bridge arm is as follows: assuming that x (a, b, c) represents three phases of the power frequency and y (u, v, w) represents three phases of the low frequency, nine bridge arms are identified by xy; if the bridge arm withdrawn due to fault is x0y0Then select and x again0And y0Two irrelevant bridge arms are withdrawn, and the withdrawn bridge arm identifications are not the same in x and y.
9. The fault-tolerant operation device of a low-frequency power transmission system according to claim 6, wherein in the bridge arm fault unit, after a nine-bridge arm is switched to a six-bridge arm for operation, the fault-tolerant operation device is constrained by the formula (1), wherein Q issIs reactive power, Q, of the M3C power frequency sidelIs reactive power, V, of the low frequency side of M3CNOIs a neutral point of low frequency system, IcirIs a six-arm M3C circulating current, as shown in formula (2), wherein k is 1,2, …,6, ibkIs the bridge arm current;
Figure FDA0003587395180000031
Figure FDA0003587395180000032
after the six-bridge arm is switched to, V is required to be met in order to ensure that the six-bridge arm M3C normally operatesNOWhen Q is equal to 0, Q is controlledsAnd QlEqual to zero, or QsAnd QlThe direction is opposite.
10. The fault-tolerant operation device of a low-frequency transmission system according to claim 6, wherein in the line fault unit, after the single-phase line is isolated due to the permanent fault, the sub frequency conversion valve connected with the fault is locked, two sub frequency conversion valves connected with the other two phases continue to operate, and the low-frequency side outputs the low-frequency voltage with the phase angle difference of 180 degrees.
CN202210369374.5A 2022-04-08 2022-04-08 Fault-tolerant operation method and device for low-frequency power transmission system Pending CN114696359A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116148589A (en) * 2022-11-15 2023-05-23 合肥工业大学 Simplified analysis method and system for fault current of low-frequency power transmission system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116148589A (en) * 2022-11-15 2023-05-23 合肥工业大学 Simplified analysis method and system for fault current of low-frequency power transmission system
CN116148589B (en) * 2022-11-15 2023-09-19 合肥工业大学 Simplified analysis method and system for fault current of low-frequency power transmission system

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