CN108616110B - Protection device of alternating current-direct current interconnection system - Google Patents
Protection device of alternating current-direct current interconnection system Download PDFInfo
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- CN108616110B CN108616110B CN201611129613.0A CN201611129613A CN108616110B CN 108616110 B CN108616110 B CN 108616110B CN 201611129613 A CN201611129613 A CN 201611129613A CN 108616110 B CN108616110 B CN 108616110B
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- 230000004224 protection Effects 0.000 title claims abstract description 351
- 238000006243 chemical reaction Methods 0.000 claims description 53
- 230000005856 abnormality Effects 0.000 claims description 15
- 230000006855 networking Effects 0.000 claims description 8
- 239000003990 capacitor Substances 0.000 claims description 3
- 230000016507 interphase Effects 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 4
- 238000005192 partition Methods 0.000 description 3
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- 238000012986 modification Methods 0.000 description 2
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
- H02H7/262—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of switching or blocking orders
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
- H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for dc applications
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Abstract
The invention provides a protection device of an alternating current-direct current interconnection system, which comprises at least one transformer substation subsystem, wherein the transformer substation subsystem can convert alternating current input or direct current input into at least one path of direct current output and/or at least one path of alternating current output; the protection device comprises a system-level protection module and a device-level protection module, wherein the system-level protection module comprises an alternating current protection unit and a direct current protection unit, the alternating current protection unit is used for protecting an alternating current input circuit and/or an alternating current output circuit of the transformer substation subsystem, the direct current protection unit is used for protecting a direct current input circuit and/or a direct current output circuit of the transformer substation subsystem, and the device-level protection module is used for protecting a working circuit of the transformer substation subsystem. The protection range of the protection device covers the whole circuit of the AC/DC interconnection system and elements in the circuit, the protection ranges of all stages of areas are clear and mutually matched, no protection dead zone exists, and the fault-free part can be ensured to continue to operate while the fault area is isolated.
Description
Technical Field
The invention relates to the technical field of power supply protection, in particular to a protection device of an alternating current-direct current interconnection system.
Background
In recent years, a large amount of distributed power supplies and direct current loads are connected into a public power grid, an alternating current power supply and a direct current power supply coexist in the power grid, and the demand of an alternating current-direct current hybrid power supply mode is provided for the power grid. Meanwhile, the development of the power electronics technology is rapid, and the power supply system is applied to a large scale in a power system, so that the power grid is possible to be converted from a traditional alternating current power supply mode to an alternating current and direct current hybrid power supply mode. The alternating current-direct current interconnection system can realize the classification of the power supply reliability and meet the differentiated power supply requirements of users.
However, the topology of the ac/dc interconnection system is diverse and the wiring is complex, so that the protection configuration and setting are also more complex. Unlike the independent traditional AC protection and DC protection, the AC-DC interconnection system needs AC-DC protection cooperation, ensures the safety of equipment and the system, quickly isolates fault circuits, ensures the continuous operation of fault-free parts, and improves the safety and reliability of power supply.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is that the topological structure of the AC/DC interconnection system is various, the wiring is complex, and the circuit protection requirement is high.
Therefore, the embodiment of the invention provides the following technical scheme:
the utility model provides a protection device of alternating current-direct current interconnection system, alternating current-direct current interconnection system includes at least one transformer substation subsystem, and the transformer substation subsystem is used for changing alternating current input or direct current input into at least one way direct current output and/or at least one way alternating current output, includes:
the system-level protection module comprises an alternating current protection unit and a direct current protection unit, wherein the alternating current protection unit is used for protecting an alternating current input circuit and/or an alternating current output circuit of the substation subsystem, and the direct current protection unit is used for protecting a direct current input circuit and/or a direct current output circuit of the substation subsystem; and
and the device-level protection module is used for protecting the working circuit of the substation subsystem.
Optionally, the direct current output of the substation subsystem is connected with the direct current load circuit, the alternating current output is connected with the alternating current load circuit, and the system-level protection module further comprises a load protection unit, wherein the load protection unit is used for protecting the direct current load circuit and/or the alternating current load circuit.
Optionally, the working circuit of the substation subsystem comprises at least one path of conversion circuit, the conversion circuit is used for converting direct current voltage into alternating current voltage or converting direct current voltage into direct current voltage with different voltage magnitudes or converting alternating current voltage into alternating current voltage with different voltage magnitudes, the at least one path of conversion circuit comprises a conversion bridge circuit, the conversion bridge circuit of the at least one path of conversion circuit comprises a conversion switch, the device-level protection module comprises a sub-module protection unit, a conversion bridge protection unit and a conversion switch protection unit, the sub-module protection unit is used for protecting the conversion circuit, the conversion bridge protection unit is used for protecting the conversion bridge circuit in the conversion circuit, and the conversion switch protection unit is used for protecting the conversion switch in the conversion bridge circuit.
Optionally, the ac protection unit includes a differential protection subunit, an over-current protection subunit, and a voltage abnormality protection subunit.
Optionally, the dc protection unit includes a low voltage over-current protection subunit, an over-current protection subunit, a directional over-current protection subunit, a line differential protection subunit, a voltage unbalance protection subunit, a single/bipolar low voltage protection subunit, and a single/bipolar over-voltage protection subunit.
Optionally, the load protection unit includes a differential protection subunit, an over-current protection subunit, a directional over-current protection subunit, a voltage unbalance protection subunit, a single/bipolar low voltage protection subunit, a single/bipolar over-voltage protection subunit, and a voltage abnormality protection subunit.
Optionally, the device-level protection module includes a differential protection subunit, an over-current protection subunit, and a submodule capacitor voltage protection unit.
Optionally, the dc output of the substation subsystem is connected to a dc bus of the same voltage class, and the dc protection unit comprises a dc bus differential protection subunit.
Optionally, the ac output of the substation subsystem is connected to an ac bus of the same voltage class, and the ac protection unit comprises an ac bus differential protection subunit.
Optionally, the input end of the substation subsystem is connected with the distributed power supply, and a networking protection unit is arranged between the input end of the substation subsystem and the distributed power supply, and comprises an anti-islanding protection subunit, a low/overvoltage protection subunit, a low/over-frequency protection subunit, a fault disconnection subunit and a reclosing subunit.
Optionally, a differential protection subunit in the ac protection unit is configured to reflect the fault and act to trip to isolate a portion of the circuit of the fault; the overcurrent protection subunit and the voltage abnormality protection subunit in the alternating current protection unit are used for delaying the preset time to act so as to cut off a part of a fault circuit or send an alarm signal when the differential protection subunit does not act normally.
Optionally, for a high current grounding system, the protection outlet of the ac protection unit trips to isolate the failed part of the circuit, and the rest of the ac-dc interconnection system can continue to supply power to the load; if a single substation subsystem is to supply power to a load alone, then either a direct current or an alternating current input is required.
Optionally, for a low-current grounding system, when an interphase fault occurs, a protection outlet of the alternating current protection unit trips to isolate a part of a circuit of the fault, and the rest part of the alternating current-direct current interconnection system can continue to supply power for a load; when single-phase grounding occurs, if a single substation subsystem operates independently, the single substation subsystem can continue to operate according to the system requirement, and a voltage abnormality protection subunit sends an alarm signal; if more than two substation subsystems are in interconnected operation, the operation can be continued according to the system requirement, and a contact switch between the substation subsystem connected with the fault circuit and other substation subsystems is disconnected.
Optionally, the direct current protection unit is used for cutting off a part of the circuit with faults, and the circuit of other non-fault parts of the alternating current-direct current interconnection system continues to operate;
the low-voltage overcurrent protection subunit in the direct-current protection unit is used for being used as the main protection of the protected circuit;
the overcurrent protection subunit, the voltage unbalance protection subunit, the single/bipolar low-voltage protection subunit and the single/bipolar overvoltage protection subunit in the direct-current protection unit are used as backup protection of a protected circuit;
the line differential protection subunit and the direction overcurrent protection subunit in the direct current protection unit are used for positioning faults.
Optionally, the load protection unit is used for cutting off a fault branch in the direct current load circuit or the alternating current load circuit, and the rest parts without faults continue to operate.
The technical scheme of the invention has the following advantages:
1. the protection device for the alternating current-direct current interconnection system provided by the embodiment of the invention adopts a grading principle to carry out grading protection on the alternating current-direct current interconnection system according to a system level and a device level, and adopts a partitioning principle to divide a system level protection module into an alternating current protection unit and a direct current protection unit so as to respectively protect alternating current and direct current circuits in the alternating current-direct current interconnection system. The device-level protection module is mainly used for protecting power electronic working circuits in the substation subsystem. Therefore, the protection range of the protection device covers the whole circuit of the AC/DC interconnection system and elements in the circuit, the protection ranges of all stages of areas are clear and mutually matched, and no protection dead zone exists. In addition, the protection mode of the grading partition can rapidly locate the fault area to rapidly cut off the related circuits, so that the normal operation of the fault-free area is ensured. The protection device can be applied to an ac/dc interconnection system interconnected by any form.
2. The protection device of the AC/DC interconnection system provided by the embodiment of the invention performs layered protection on the working circuits of the substation subsystems in the system according to the principle of progressive layer by layer, firstly, the submodule protection unit is used for integrally protecting each conversion circuit in the substation subsystems, then the conversion bridge protection unit is used for protecting part of key circuits in the conversion circuits, and finally, the conversion switch protection unit is used for protecting key elements in the conversion circuits. Therefore, the safety and the reliability of the working circuit in the core circuit-transformer substation subsystem in the alternating current-direct current interconnection system are ensured to the greatest extent by utilizing multiple protections, so that the power supply reliability of the whole interconnection system and the electricity utilization safety of users are ensured. In addition, the multi-layer protection mode can ensure the safety of key circuits and the safety of key elements in the multi-layer protection mode to the greatest extent, and can timely distinguish fault circuits and non-fault circuits by a substation subsystem, and timely cut off the fault circuits to ensure the safe operation of other non-fault circuits.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram illustrating protection division of an ac/dc interconnection system according to an embodiment of the present invention;
FIG. 2 is a topology diagram of an AC/DC interconnect system to which embodiments of the present invention may be applied;
FIG. 3 is a schematic diagram illustrating the protection scheme of the AC/DC interconnection system shown in FIG. 2;
fig. 4 is a schematic diagram illustrating protection of another ac/dc interconnection system according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "connected," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; the two components can be directly connected or indirectly connected through an intermediate medium, or can be communicated inside the two components, or can be connected wirelessly or in a wired way. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Examples
As shown in fig. 1, the present embodiment provides a protection device for an ac/dc interconnection system, where the ac/dc interconnection system includes at least one substation subsystem, and the substation subsystem may convert an ac input or a dc input into at least one path of dc output and at least one path of ac output, or may output only an ac voltage or only a dc voltage; the protection device comprises a system-level protection module and a device-level protection module, wherein the system-level protection module comprises an alternating current protection unit and a direct current protection unit, the alternating current protection unit is used for protecting an alternating current input circuit and/or an alternating current output circuit of the transformer substation subsystem, the direct current protection unit is used for protecting a direct current input circuit and/or a direct current output circuit of the transformer substation subsystem, and the device-level protection module is used for protecting a working circuit of the transformer substation subsystem.
The protection device for the ac/dc interconnection system provided in this embodiment adopts a classification principle to perform classification protection on the ac/dc interconnection system according to a system level and a device level, and adopts a partition principle to divide a system level protection module into an ac protection unit and a dc protection unit to respectively protect an ac circuit and a dc circuit in the ac/dc interconnection system, which mainly refers to an ac circuit portion and a dc circuit portion. The device-level protection module is mainly used for protecting power electronic working circuits in the substation subsystem. Therefore, the protection range of the protection device covers the whole circuit (including a power transmission line) of the AC/DC interconnection system and elements in the circuit, the protection ranges of all stages of areas are clear and mutually matched, and no protection dead zone exists. In addition, the protection mode of the grading partition can rapidly locate the fault area to rapidly cut off the related circuits, so that the normal operation of the fault-free area is ensured. The protection device can be applied to an ac/dc interconnection system interconnected by any form.
As other specific embodiments, the working circuit of the substation subsystem includes at least one converting circuit, where the converting circuit is configured to convert a direct current voltage into an alternating current voltage or convert a direct current voltage into a direct current voltage with a different voltage magnitude or convert an alternating current voltage into an alternating current voltage with a different voltage magnitude. The working circuit of the substation subsystem can also comprise four or more conversion circuits to respectively realize the four voltage conversions. The device-level protection module comprises a submodule protection unit, a conversion bridge protection unit and a conversion switch protection unit, wherein the submodule protection unit is used for protecting the conversion circuit, the conversion bridge protection unit is used for protecting the conversion bridge circuit in the conversion circuit, and the conversion switch protection unit is used for protecting the conversion switch in the conversion bridge circuit. Specifically, each protection unit in the device-level protection module specifically includes at least one of a differential protection subunit and an overcurrent protection subunit, and the device-level protection module may further include a submodule capacitor voltage protection unit.
According to the protection device of the AC/DC interconnection system, provided by the embodiment, the working circuits of the substation subsystems in the system are protected in a layered manner according to the principle of progressive layer by layer, all conversion circuits in the substation subsystems are integrally protected by using the submodule protection units, part of key circuits in the conversion circuits are protected by using the conversion bridge protection units, and key elements in the conversion circuits are protected by using the conversion switch protection units. Therefore, the safety and the reliability of the working circuit in the core circuit-transformer substation subsystem in the alternating current-direct current interconnection system are ensured to the greatest extent by utilizing multiple protections, so that the power supply reliability of the whole interconnection system and the electricity utilization safety of users are ensured. In addition, the multi-layer protection mode can ensure the safety of key circuits and the safety of key elements in the multi-layer protection mode to the greatest extent, can timely distinguish fault circuits and non-fault circuits in working circuits of the substation subsystems, and timely cuts off the fault circuits to ensure the safe operation of other non-fault circuits.
Specifically, the ac protection unit includes at least one of a differential protection subunit, an overcurrent protection subunit, and a voltage abnormality protection subunit. The alternating current protection unit can also comprise three protection subunits at the same time, wherein differential protection is mainly adopted, and when faults occur, partial circuits with faults are isolated through tripping; the overcurrent protection and the voltage abnormality protection are used as backup protection, and when the main protection, namely the differential protection does not normally operate, the circuit for cutting off the fault part or sending an alarm signal is delayed for a certain time.
For a high-current grounding system, a protection outlet of the alternating current protection unit trips a circuit for isolating a fault part, and the rest parts of the alternating current-direct current interconnection system can continue to supply power for loads; if a single substation subsystem is to supply power to a load alone, then either a direct current or an alternating current input is required.
For a small-current grounding system, when an interphase fault occurs, the protection outlet of the alternating current protection unit is the same as that of the large-current grounding system; when single-phase grounding occurs, if the single substation subsystem operates independently, the single substation subsystem can continue to operate according to the system requirement, the voltage abnormality protection subunit sends an alarm signal, and a circuit of a fault part can be disconnected without tripping until a line selection device or other measures find out faults. If two or more substation subsystems are in interconnected operation, the operation can be continued according to the system requirements, and meanwhile, the substation subsystem connected with the fault circuit can be disconnected from the interconnection switches of other substation subsystems.
The direct current protection unit comprises one or more of a low-voltage overcurrent protection subunit, an overcurrent protection subunit, a directional overcurrent protection subunit, a line differential protection subunit, a voltage unbalance protection subunit, a single/bipolar low-voltage protection subunit and a single/bipolar overvoltage protection subunit. The low-voltage overcurrent protection subunit is used as a fast protection, and only the protected circuit simultaneously meets the requirements of low voltage and overcurrent. The low-voltage overcurrent protection subunit is used for main protection of a protected circuit, the overcurrent protection subunit, the voltage unbalance protection subunit, the single/bipolar low-voltage protection subunit and the single/bipolar overvoltage protection subunit are used for backup protection of the protected circuit, and the line differential protection subunit and the directional overcurrent protection subunit are used for positioning circuit faults. When the protection situation occurs, the fault part circuit or element is cut off, and other fault-free part circuits of the AC/DC interconnection system continue to normally operate.
As a specific implementation manner, the direct current output of the substation subsystem may be connected to a direct current load circuit, the alternating current output may be connected to an alternating current load circuit, and correspondingly, the system-level protection module further includes a load protection unit, where the load protection unit is used to protect the direct current load circuit and/or the alternating current load circuit connected to the output end of the substation subsystem. The load protection unit comprises one or more of a differential protection subunit, an overcurrent protection subunit, a directional overcurrent protection subunit, a voltage unbalance protection subunit, a single/bipolar low-voltage protection subunit, a single/bipolar overvoltage protection subunit and a voltage abnormality protection subunit. When the load protection circuit has the fault protection, only fault branches in the direct current load circuit or the alternating current load circuit are cut off, and the rest parts without faults continue to operate.
As a specific implementation mode, the direct current output of the substation subsystems can be connected with the direct current buses of the same voltage class, namely the same-level direct current voltages output by different substation subsystems can be collected on the same direct current bus, and the direct current protection unit further comprises a direct current bus differential protection subunit.
The AC output of the transformer substation subsystems can be connected with AC buses of the same voltage class, namely the same-class AC voltages output by different transformer substation subsystems can be collected on the same AC bus, and the AC protection unit further comprises an AC bus differential protection subunit.
In addition, the direct current output or the alternating current output of the substation subsystem may not be connected to the bus. The same voltage class outputs of different substation subsystems can be interconnected, or can be independently connected with a load, such as an electric automobile.
As another specific embodiment, the input end of the substation subsystem is connected to a distributed power source, for example, a photovoltaic distributed power source, a wind power distributed power source, or other distributed power sources, which are not limited herein. And a networking protection unit is arranged between the input end of the substation subsystem and the distributed power supply, and comprises an anti-islanding protection subunit, a low/overvoltage protection subunit, a low/over-frequency protection subunit and a fault disconnection and reclosing subunit. In addition, the distributed power supply can be connected with the substation subsystem through a converter, and the converter can be a DC/DC converter which converts the direct current voltage output by the distributed power supply into the direct current voltage of the same grade as the input voltage of the substation subsystem and then is connected with the direct current input end of the substation subsystem. The converter may be a DC/AC converter which converts the DC voltage output from the distributed power supply to an AC voltage of the same class as the input voltage of the substation subsystem and is connected to the AC input thereof.
The protection device for an AC/DC interconnection system provided in this embodiment may be applied to an AC/DC interconnection system shown in fig. 2, where a transformer in an AC/DC/AC form may be used in a transformer substation of the AC/DC/AC, and the transformer substation inputs AC, outputs two DC/s with different voltage levels, and outputs one AC. The output direct current DC may be connected to a direct current bus which connects a plurality of DC branches of the same voltage class. Specifically, the direct current bus 1-1 gathers the direct current circuit 1-2, the direct current circuit 1-1 and the DC circuit output by the transformer substation; the direct current bus 2-1 collects the direct current line 1-3, the direct current line 1-1 and the direct current line output by another transformer substation. The direct current bus 1-2 collects a direct current load 1-1 circuit, a direct current load 1-2 circuit and a direct current circuit 2-1 output by a transformer substation; the direct current bus 2-2 collects direct current load 2-1 lines, direct current load 2-2 lines and direct current lines 2-2 output by the transformer substation. The output AC may be connected to an AC bus, connecting a plurality of AC loads, in particular: the low-voltage alternating current line 1 is connected to the alternating current bus 1-1, the alternating current load 1-1 and the alternating current load 1-2 are connected, the low-voltage alternating current line 2 is connected to the alternating current bus 2-1, and the alternating current load 2-1 and the alternating current load 2-2 are connected. The transformer in the AC/DC/AC mode can be adopted by the AC/DC interconnection system transformer substation, and the AC/DC is input and one path of DC and one path of AC are output.
The protection of the ac/dc interconnection system by using the protection device provided in this embodiment is shown in fig. 3. The ac line 1, the ac line 2, the ac bus 1-1, the ac bus 2-1, the low voltage ac line 1 and the low voltage ac line 2 are ac protected, wherein the ac protection includes one or more of differential protection, overcurrent protection and voltage abnormality protection, but is not limited to these three types. In addition, the protection of the ac bus 1-1 and the ac bus 2-1 also includes an ac bus differential protection in which the low-voltage ac line 1 and the low-voltage ac line 2 can be protected separately from other ac lines.
The direct current circuit 1-2, the direct current circuit 1-1, the direct current circuit 1-3, the direct current circuit 2-1, the direct current circuit 2-2, the direct current bus 1-1, the direct current bus 2-1, the direct current bus 1-2 and the direct current bus 2-2 are subjected to direct current protection, wherein the direct current protection specifically comprises, but is not limited to, low voltage overcurrent protection, directional overcurrent protection, circuit differential protection, voltage unbalance protection, single/bipolar low voltage protection and single/bipolar overvoltage protection, and one or more of the direct current protection and the direct current protection can be selected. The direct current protection of the direct current bus 1-1, the direct current bus 2-1, the direct current bus 1-2 and the direct current bus 2-2 further comprises direct current bus differential protection. In addition, the direct current line 2-1 and the direct current line 2-2 can be protected separately from other direct current lines.
The direct current load 1-1, the direct current load 1-2, the direct current load 2-1 and the direct current load 2-2 are subjected to direct current load protection, wherein the direct current load protection comprises, but is not limited to, overcurrent protection, directional overcurrent protection, line differential protection, voltage unbalance protection, single/bipolar low voltage protection and single/bipolar overvoltage protection, and one or more of the direct current load protection, the direct current load protection and the direct current load 2-2 can be selected. The alternating current load 1-1, the alternating current load 1-2, the alternating current load 2-1 and the alternating current load 2-2 are subjected to alternating current load protection, wherein the alternating current load protection comprises, but is not limited to, overcurrent protection, directional overcurrent protection and voltage abnormality protection, and only one of the alternating current load protection, the direct overcurrent protection and the voltage abnormality protection can be selected.
In addition, the protection device for an ac/dc interconnection system provided in this embodiment may be further applicable to an ac/dc interconnection system shown in fig. 4, where the ac/dc interconnection system is different from the ac/dc interconnection system shown in fig. 2 in that: the direct current circuit 1-3 is connected with a distributed power supply through a DC/DC converter, so that the networking of the distributed power supply is realized. Correspondingly, networking protection is further arranged on the networking side of the distributed power supply, and the networking protection specifically comprises anti-islanding protection, low/overvoltage protection, low/over-frequency protection, fault disconnection and reclosing.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (13)
1. A protection device for an ac/dc interconnection system, the ac/dc interconnection system including at least one substation subsystem, the substation subsystem being configured to convert an ac input or a dc input into at least one path of dc output and/or at least one path of ac output, the protection device comprising:
the system-level protection module comprises an alternating current protection unit and a direct current protection unit, wherein the alternating current protection unit is used for protecting an alternating current input circuit and/or an alternating current output circuit of the transformer substation subsystem, and the direct current protection unit is used for protecting a direct current input circuit and/or a direct current output circuit of the transformer substation subsystem; and
the device-level protection module is used for protecting a working circuit of the substation subsystem;
the working circuit of the transformer substation subsystem comprises at least one path of conversion circuit, wherein the conversion circuit is used for converting direct current voltage into alternating current voltage or converting direct current voltage into direct current voltage with different voltage magnitudes or converting alternating current voltage into alternating current voltage with different voltage magnitudes, at least one path of conversion circuit comprises a conversion bridge circuit, at least one path of conversion bridge circuit of the conversion circuit comprises a conversion switch, the device-level protection module comprises a sub-module protection unit, a conversion bridge protection unit and a conversion switch protection unit, the sub-module protection unit is used for protecting the conversion circuit, the conversion bridge protection unit is used for protecting the conversion bridge circuit in the conversion circuit, and the conversion switch protection unit is used for protecting the conversion switch in the conversion bridge circuit;
the direct current protection unit comprises a low-voltage overcurrent protection subunit, an overcurrent protection subunit, a directional overcurrent protection subunit, a line differential protection subunit, a voltage unbalance protection subunit, a single/bipolar low-voltage protection subunit and a single/bipolar overvoltage protection subunit.
2. The protection device of an ac/dc interconnection system according to claim 1, wherein a dc output of the substation subsystem is connected to a dc load circuit, an ac output is connected to an ac load circuit, and the system level protection module further comprises a load protection unit, and the load protection unit is configured to protect the dc load circuit and/or the ac load circuit.
3. The protection device of an ac-dc interconnection system according to any one of claims 1-2, wherein the ac protection unit includes a differential protection subunit, an overcurrent protection subunit, and a voltage abnormality protection subunit.
4. The protection device of an ac/dc interconnection system according to claim 2, wherein the load protection unit includes a differential protection subunit, an overcurrent protection subunit, a directional overcurrent protection subunit, a voltage unbalance protection subunit, a single/bipolar low voltage protection subunit, a single/bipolar overvoltage protection subunit, and a voltage abnormality protection subunit.
5. The protection device of an ac/dc interconnection system according to claim 4, wherein said device level protection module comprises a differential protection subunit, an over-current protection subunit, and a submodule capacitor voltage protection unit.
6. The ac/dc interconnect system protection device of claim 5, wherein the dc output of the substation subsystem is connected to a dc bus of the same voltage level, and the dc protection unit comprises a dc bus differential protection subunit.
7. The ac/dc interconnect system of claim 5 wherein the ac output of the substation subsystem is connected to an ac bus of the same voltage level and the ac protection unit comprises an ac bus differential protection subunit.
8. The protection device of an ac/dc interconnection system according to claim 6, wherein an input end of the substation subsystem is connected to a distributed power source, and a networking protection unit is disposed between the input end of the substation subsystem and the distributed power source, and the networking protection unit includes an anti-islanding protection subunit, a low/overvoltage protection subunit, a fault disconnection subunit, and a reclosing subunit.
9. A protection device for an ac/dc interconnection system according to claim 3, wherein said differential protection subunit of said ac protection unit is configured to reflect a fault and act to trip to isolate a portion of the circuit from the fault; the over-current protection subunit and the voltage abnormality protection subunit in the alternating current protection unit are used for delaying a preset time to act so as to cut off a part of a fault circuit or send an alarm signal when the differential protection subunit does not act normally.
10. A protection device for an ac/dc interconnection system according to claim 3, wherein for high current grounding systems, the protection outlet of the ac protection unit trips to isolate the faulty partial circuit, the rest of the ac/dc interconnection system continuing to supply power to the load; if a single substation subsystem is to supply power to a load alone, then either a direct current or an alternating current input is required.
11. A protection device for an ac/dc interconnection system according to claim 3, wherein for a low current ground system, when an inter-phase fault occurs, a protection outlet of the ac protection unit trips to isolate a part of the circuit of the fault, and the rest of the ac/dc interconnection system can continue to supply power to a load; when single-phase grounding occurs, if a single substation subsystem operates independently, the operation can be continued according to the system requirement, and an alarm signal is sent by the voltage abnormality protection subunit; if more than two substation subsystems are in interconnected operation, the operation can be continued according to the system requirement, and a contact switch between the substation subsystem connected with the fault circuit and other substation subsystems is disconnected.
12. The protection device of an ac/dc interconnection system according to claim 4, wherein the dc protection unit is configured to cut off a portion of a circuit that is faulty, and the circuit of the other non-faulty portion of the ac/dc interconnection system continues to operate;
the low-voltage overcurrent protection subunit in the direct-current protection unit is used for being used as the main protection of a protected circuit;
the overcurrent protection subunit, the voltage unbalance protection subunit, the single/bipolar low-voltage protection subunit and the single/bipolar overvoltage protection subunit in the direct-current protection unit are used as backup protection of a protected circuit;
the line differential protection subunit and the direction overcurrent protection subunit in the direct current protection unit are used for positioning faults.
13. The protection device of an ac/dc interconnection system according to claim 2 or 5, wherein the load protection unit is configured to cut off a fault branch in the dc load circuit or the ac load circuit, and the remaining non-fault portion continues to operate.
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| CN111900696B (en) * | 2020-07-15 | 2022-08-23 | 中国人民解放军海军工程大学 | Shore power relay protection system and method for AC-DC coexistence power supply |
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