CN106921157A - A kind of AC singlephase earth fault control method of flexible ring net controller - Google Patents

A kind of AC singlephase earth fault control method of flexible ring net controller Download PDF

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Publication number
CN106921157A
CN106921157A CN201511001470.0A CN201511001470A CN106921157A CN 106921157 A CN106921157 A CN 106921157A CN 201511001470 A CN201511001470 A CN 201511001470A CN 106921157 A CN106921157 A CN 106921157A
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China
Prior art keywords
phase
voltage
converter
network controller
flexible ring
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CN201511001470.0A
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CN106921157B (en
Inventor
阳岳希
高凯
庞辉
李强
邵宝珠
别晓玉
马巍巍
李胜辉
李洪志
许韦华
张潇桐
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Electric Power Research Institute of State Grid Liaoning Electric Power Co Ltd
State Grid Smart Grid Research Institute of SGCC
State Grid Corp of China SGCC
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Electric Power Research Institute of State Grid Liaoning Electric Power Co Ltd
State Grid Smart Grid Research Institute of SGCC
State Grid Corp of China SGCC
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—ELECTRIC POWER NETWORKS; 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for AC mains or AC distribution networks
    • H02J3/36—Arrangements for transfer of electric power between AC networks via high-voltage DC [HVDC] links; Arrangements for transfer of electric power between generators and networks via HVDC links
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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

Abstract

本发明提供了一种柔性环网控制器的交流侧单相接地故障控制方法，包括步骤1：实时检测交流系统的三相电压；步骤2：判断交流系统是否发生单相接地故障；步骤3：获取非故障相的电压峰值的最大值；步骤4：重新确定交流系统的直流电压指令值；步骤5：启动负序电流控制和零序电流控制；步骤6：判断单相接地故障是否清除，若清除则将述直流电压指令值恢复至交流系统正常运行时的直流电压指令值。与现有技术相比，本发明提供的一种柔性环网控制器的交流侧单相接地故障控制方法，在交流侧发生单相接地故障期间，短时降低直流电压，利用混合子模块结构的负电压输出能力，使交流电流仍然保持三相对称的正弦波形，提高了柔性环网控制器的可靠性。

The invention provides a method for controlling a single-phase ground fault on the AC side of a flexible ring network controller, comprising step 1: detecting the three-phase voltage of the AC system in real time; step 2: judging whether a single-phase ground fault occurs in the AC system; step 3: Obtain the maximum value of the voltage peak value of the non-fault phase; Step 4: Re-determine the DC voltage command value of the AC system; Step 5: Start negative sequence current control and zero sequence current control; Step 6: Determine whether the single-phase ground fault is cleared, if Clearing restores the DC voltage command value to the DC voltage command value when the AC system is in normal operation. Compared with the prior art, the present invention provides a method for controlling a single-phase ground fault on the AC side of a flexible ring network controller. When a single-phase ground fault occurs on the AC side, the DC voltage is reduced for a short time, and the hybrid sub-module structure is used. The negative voltage output capability keeps the AC current in a three-phase symmetrical sinusoidal waveform, which improves the reliability of the flexible ring network controller.

Description

Alternating-current side single-phase earth fault control method of flexible ring network controller
Technical Field
The invention relates to the technical field of power electronics, in particular to a method for controlling a single-phase earth fault at an alternating current side of a flexible ring network controller.
Background
With the continuous increase of transmission load, the development of power grid is established, and the electromagnetic ring network is continuously formed. The existing general method for disconnecting the electromagnetic ring network is to add an alternating current breaker at a disconnecting point or implement the partitioned operation of the power grid, but the precondition of the method is that the power grid has the basic condition of the open-loop operation. When the electromagnetic ring network is difficult to operate in an open loop mode and meets the condition of safety constraint, technologies such as a unified power flow controller, a phase shifter, an interphase power controller, a controllable series compensation and the like can be adopted, and voltage phase angles are adjusted through an FACTS device, so that circulation currents in the electromagnetic ring network are eliminated, short-circuit currents are limited, power distribution between high/low voltage networks is optimized, and the operation reliability and economy of a system are improved. The flexible ring network controller is back-to-back flexible direct current, and can realize the rapid independent control of active power and reactive power; when the alternating current system breaks down, the flexible direct current does not provide short-circuit current, the fault can be isolated rapidly, and the device has a black start function, and provides a choice for solving the problem of the electromagnetic looped network.
However, when the converter-less transformer is adopted to construct the flexible ring network controller system scheme of the converter based on the hybrid submodule, when the alternating current system has a ground short circuit fault, the fault voltage can directly act on the converter due to the fact that the converter transformer is not isolated, so that large fault voltage stress and current stress are caused, and equipment damage is easily caused. Therefore, it is necessary to provide a fault control method capable of reducing the dc voltage for a short time during a single-phase ground fault on the ac side, and preventing the fault from being transmitted to the other ac system.
Disclosure of Invention
In order to meet the needs of the prior art, the present invention provides a method for controlling an ac-side single-phase ground fault of a flexible looped network controller.
The technical scheme of the invention is as follows:
the method comprises the following steps:
step 1: detecting the three-phase voltage of an alternating current system in real time;
step 2: judging whether the alternating current system has a single-phase earth fault;
and step 3: obtaining the maximum value U of the voltage peak value of a non-fault phase after the single-phase earth fault of the alternating current system occurss_max；
And 4, step 4: redetermining direct-current voltage command value U 'of alternating-current system'd；
And 5: starting negative sequence current control and zero sequence current control;
step 6: judging whether the single-phase earth fault is cleared or not, and if so, judging that the direct-current voltage instruction value U'dRestoring the direct current voltage instruction value U to the normal operation of the alternating current systemd。
Preferably, in step 2, when the voltage of one phase of the ac system is reduced to 0 and the voltages of the other two phases are rapidly increased, a single-phase ground fault occurs in the ac system.
Preferably, the DC voltage command value U 'in step 4'dThe value range is as follows: u'd＜3Ud-2Us_max；
Wherein, UdThe direct current voltage instruction value is the direct current voltage instruction value when the alternating current system normally operates.
Preferably, the topology of the flexible ring network controller comprises a first converter and a second converter; the first converter and the second converter are both directly connected to an alternating current system;
each phase of half-bridge arm of the first converter is formed by connecting a full-bridge sub-module and at least one half-bridge sub-module in series;
each phase half bridge arm of the second converter is also formed by connecting a full-bridge submodule and at least one half-bridge submodule in series.
Compared with the closest prior art, the excellent effects of the invention are as follows:
1. the alternating-current side single-phase earth fault control method of the flexible ring network controller can completely inhibit overvoltage and overcurrent at the alternating-current side, prevent a current converter from bearing overhigh fault voltage and current, and improve the service life of equipment and the reliability of a system;
2. according to the alternating current side single-phase earth fault control method of the flexible ring network controller, the fluctuation of direct current voltage does not exceed +/-1%, the fluctuation of direct current is suppressed within +/-20%, and power electronic devices in a converter can be prevented from being damaged due to overcurrent;
3. according to the alternating current side single-phase earth fault control method of the flexible ring network controller, during the period that the single-phase earth fault occurs on the alternating current side, the direct current voltage is reduced for a short time, the negative voltage output capability of the hybrid submodule structure is utilized, the alternating current output by the converter station still keeps a three-phase symmetrical sine waveform, the fault component can be restrained, the fault is prevented from being transmitted to an alternating current system on the other side, and the reliability of the flexible ring network controller is improved.
Drawings
The invention is further described below with reference to the accompanying drawings.
FIG. 1: the topological structure schematic diagram of the flexible ring network controller in the embodiment of the invention;
FIG. 2: the response oscillogram of the half-bridge submodule in the normal operation of the alternating current system in the embodiment of the invention;
FIG. 3: the response waveform diagram of the half-bridge submodule in the embodiment of the invention when the single-phase earth fault occurs in the alternating current system;
FIG. 4: in the embodiment of the invention, the response oscillogram of the mixing submodule during the normal operation of the alternating current system is shown;
FIG. 5: the response oscillogram of the hybrid submodule in the embodiment of the invention when the single-phase earth fault occurs in the alternating-current system;
FIG. 6: the invention discloses a flow chart of an alternating-current side single-phase earth fault control method of a flexible ring network controller;
FIG. 7: the embodiment of the invention provides an alternating voltage oscillogram during fault-free control;
FIG. 8: the embodiment of the invention provides an alternating current oscillogram during fault-free control;
FIG. 9: the direct-current voltage oscillogram during the fault-free control in the embodiment of the invention;
FIG. 10: in the embodiment of the invention, a direct current waveform diagram is used during fault-free control;
FIG. 11: in the embodiment of the invention, an alternating voltage oscillogram during fault control is added;
FIG. 12: in the embodiment of the invention, an alternating current waveform diagram during fault control is added;
FIG. 13: in the embodiment of the invention, a direct-current voltage oscillogram during fault control is added;
FIG. 14: in the embodiment of the invention, a direct current waveform diagram during fault control is added.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
An embodiment of a method for controlling a single-phase ground fault on an ac side of a flexible ring network controller according to the present invention is shown in fig. 6, and specifically includes:
1. and detecting the three-phase voltage of the alternating current system in real time.
2. And judging whether the alternating current system has single-phase earth fault.
In this embodiment, when it is detected that the voltage of one phase of the ac system is reduced to 0 and the voltages of the other two phases are rapidly increased, a single-phase ground fault occurs in the ac system.
3. Obtaining the maximum value U of the voltage peak value of a non-fault phase after a single-phase earth fault occurs in an alternating-current systems_max。
4. Redetermining DC voltage command value U 'of AC system'd。
DC Voltage instruction value U 'in this embodiment'dThe value range is as follows: u'd＜3Ud-2Us_max；
Wherein, UdThe direct current voltage instruction value is the direct current voltage instruction value when the alternating current system normally operates.
5. And starting negative sequence current control and zero sequence current control.
6. Judging whether the single-phase earth fault is cleared or not, and if so, obtaining a direct-current voltage instruction value U'dRestoring the direct current voltage instruction value U to the normal operation of the alternating current systemd。
The topological structure of the flexible ring network controller adopting the alternating-current side single-phase ground fault control method is shown in fig. 1, and comprises a first converter and a second converter; and the first converter and the second converter are directly connected to an alternating current system. Wherein,
each phase of half bridge arm of the first current converter is formed by connecting a full bridge submodule and at least one half bridge submodule in series, and each phase of half bridge arm of the second current converter is formed by connecting a full bridge submodule and at least one half bridge submodule in series. That is, in this embodiment, the first converter and the second converter are both converters formed by hybrid submodules.
In the embodiment, the response waveform diagrams of the half-bridge sub-module and the hybrid sub-module in normal operation of the alternating current system are respectively shown in fig. 2 and 4, and the response waveform diagrams of the half-bridge sub-module and the hybrid sub-module in single-phase ground fault of the alternating current system are respectively shown in fig. 3 and 5.
In this embodiment, when the ac-side single-phase ground fault control method is not adopted, the ac voltage waveform, the ac current waveform, the dc voltage waveform, and the dc current waveform of the flexible ring network controller are respectively shown in fig. 7, 8, 9, and 10; the ac voltage waveform, the ac current waveform, the dc voltage waveform and the dc current waveform of the flexible ring network controller after the ac side single-phase ground fault control method are shown in fig. 11, 12, 13 and 14, respectively.
As can be seen from fig. 7 to 14, when the control method is not used, overvoltage and overcurrent of about 1.35 times are generated on the ac side after a fault occurs, and when the control method is used, overvoltage and overcurrent on the ac side can be completely suppressed, so that the inverter is prevented from being subjected to excessive fault voltage and current, and the service life of the equipment and the reliability of the system are improved. Meanwhile, when the control method is not adopted, the common mode oscillation fluctuation generated by the direct current voltage after the fault occurs is about +/-20%, the fluctuation generated by the direct current is about +/-130%, the fluctuation of the direct current voltage after the control method is adopted does not exceed +/-1%, the fluctuation of the direct current is restrained within +/-20%, and the power electronic devices in the converter can be prevented from being damaged due to overcurrent.
Finally, it should be noted that: the described embodiments are only some embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Claims (4)

1. An alternating-current side single-phase ground fault control method of a flexible ring network controller, the method comprising:
step 1: detecting the three-phase voltage of an alternating current system in real time;
step 2: judging whether the alternating current system has a single-phase earth fault;
and step 3: obtaining the maximum value U of the voltage peak value of a non-fault phase after the single-phase earth fault of the alternating current system occurss_max；
And 4, step 4: redetermining DC voltage fingers for the AC systemLine value of U'd；
And 5: starting negative sequence current control and zero sequence current control;
step 6: judging whether the single-phase earth fault is cleared or not, and if so, judging that the direct-current voltage instruction value U'dRestoring the direct current voltage instruction value U to the normal operation of the alternating current systemd。
2. The ac-side single-phase ground fault control method for the flexible looped network controller according to claim 1, wherein in step 2, when a voltage of one phase of the ac system drops to 0 and voltages of the other two phases rise rapidly, a single-phase ground fault occurs in the ac system.
3. The method as claimed in claim 1, wherein in step 4, the dc voltage command value U 'is provided'dThe value range is as follows: u'd＜3Ud-2Us_max；
Wherein, UdThe direct current voltage instruction value is the direct current voltage instruction value when the alternating current system normally operates.
4. The ac-side single-phase ground fault control method of the flexible ring network controller according to claim 1, wherein the topology of the flexible ring network controller includes a first converter and a second converter; the first converter and the second converter are both directly connected to an alternating current system;
each phase of half-bridge arm of the first converter is formed by connecting a full-bridge sub-module and at least one half-bridge sub-module in series;
each phase half bridge arm of the second converter is also formed by connecting a full-bridge submodule and at least one half-bridge submodule in series.
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CN110829392A (en) * 2019-11-29 2020-02-21 珠海格力电器股份有限公司 Ring network power supply system and its fault detection method and device
CN115825539A (en) * 2022-10-17 2023-03-21 盛东如东海上风力发电有限责任公司 Method and system for determining voltage and current of wind power grid-connected two-phase ground fault

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CN115825539A (en) * 2022-10-17 2023-03-21 盛东如东海上风力发电有限责任公司 Method and system for determining voltage and current of wind power grid-connected two-phase ground fault
CN115825539B (en) * 2022-10-17 2024-09-03 盛东如东海上风力发电有限责任公司 Method and system for determining voltage and current of two-phase grounding fault in wind power grid connection

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