CN114188967A - Power grid support type active current converter, control method thereof and current conversion system - Google Patents
Power grid support type active current converter, control method thereof and current conversion system Download PDFInfo
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- CN114188967A CN114188967A CN202210019831.8A CN202210019831A CN114188967A CN 114188967 A CN114188967 A CN 114188967A CN 202210019831 A CN202210019831 A CN 202210019831A CN 114188967 A CN114188967 A CN 114188967A
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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
- H02J3/36—Arrangements for transfer of electric power between AC networks via a high-tension DC link
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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
- H02H7/10—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 for converters; for rectifiers
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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- 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
- H02M3/00—Conversion of DC power input into DC power output
- H02M3/02—Conversion of DC power input into DC power output without intermediate conversion into AC
- H02M3/04—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters
- H02M3/10—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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- 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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Abstract
The application discloses a power grid support type active converter, a control method thereof and a conversion system, and belongs to the technical field of high-power electronic conversion. The power grid supporting type active converter comprises an active converter chain and a valve control system; the active current conversion chain comprises at least one active module, and the active module comprises an energy storage unit, a power control module and an energy storage control module; the power control module controls the power unit to work, the energy storage control module takes energy from an energy storage element of the energy storage unit and controls the energy storage unit to work, and the valve control system is communicated with the energy storage control module and the power control module. Through set up the energy storage control module of getting the electricity from the energy storage component in active module, can guarantee when the electric wire netting loses the electricity, energy storage control module still can normally work, realizes black start-up function in coordination with power control module.
Description
Technical Field
The application belongs to the technical field of high-power electronic current transformation, and particularly relates to a power grid support type active current converter, a control method and a current conversion system thereof.
Background
In the technical field of high-capacity high-power electronic current transformation, a multi-level current converter integrates an energy storage device into a sub-module by utilizing a modular cascade technology, has the advantages of high modularization degree, good harmonic characteristics, low equivalent switching frequency and the like, and is a standard topology in the field of high-voltage power electronics at present. The energy storage units are integrated in the modularized multi-level converter as sub-modules, for example, the energy storage units are integrated in a static var generator to realize high-voltage alternating-current direct-hanging type energy storage, or the energy storage units are integrated in a half-bridge module to realize high-voltage direct-hanging type energy storage, so that alternating-current and direct-current power conversion and energy storage can be realized simultaneously. The produced active converter is a feasible scheme which can effectively meet the access requirement of an energy storage system and play a role in supporting a power grid.
The application requirement of the multilevel converter with the energy storage unit as a black start power supply for restarting a regional power grid when the power grid loses power needs to be considered, but the existing technical scheme cannot meet the black start requirement.
Disclosure of Invention
The purpose of the invention is as follows: the application provides a power grid support type active converter, which aims to solve the technical problem that a multilevel converter in the prior art cannot be used as a black start power supply for restarting a regional power grid when the power grid loses power; the application also provides a control method of the power grid supporting type active converter, and aims to provide a plurality of selectable control modes for the power grid supporting type active converter; in addition, the application also provides a conversion system, and aims to provide an application mode of the power grid support type active converter.
The technical scheme is as follows: the power grid support type active converter comprises an active converter chain and a valve control system; wherein the active commutation chain comprises at least one active module, the active module comprising:
an energy storage unit comprising at least one energy storage element;
the power unit comprises a direct current capacitor and a power assembly which are connected in parallel, the power assembly comprises a full-bridge circuit and/or a half-bridge circuit formed by power semiconductor devices, the direct current capacitor is connected with the energy storage unit through a connecting switch, and an alternating current end of the power unit is connected with a bypass switch in parallel;
the power control module controls the power unit to work;
the energy storage control module is used for acquiring energy from the energy storage element and controlling the energy storage unit to work;
the valve control system is in communication with the energy storage control module and the power control module.
Optionally, in some embodiments, the power control module is in communication with the energy storage control module, or the power control module is integrated with the energy storage control module.
Optionally, in some embodiments, the active commutation chain includes N active modules connected in series, where N is an integer greater than or equal to 2;
the connection mode of the active current conversion chain and the valve control system comprises point-to-point connection, grouping head-to-tail connection, series random connection, series head-to-tail connection or any combination thereof; wherein,
the point-to-point connection is: in the active converter chain, all the active modules are connected with the valve control system through the respective power control module and/or the energy storage control module;
the grouping head-to-tail connection is as follows: in the active commutation chain, P active modules are in a group, and P is more than or equal to 2 and less than or equal to N; in the group, the active modules are connected in series through the power control module and/or the energy storage control module, and the power control modules and/or the energy storage control modules of the active modules at the head end and the tail end are connected with the valve control system;
the series random connection is: in the active commutation chain, all the active modules are connected in series through the power control module and/or the energy storage control module, M active modules are selected optionally, M is more than or equal to 2 and less than or equal to N, and the power control module and/or the energy storage control module are connected with the valve control system through the M active modules;
the serial connection end-to-end connection is as follows: in the active commutation chain, all the active modules are connected in series through the power control module and/or the energy storage control module, and the power control modules and/or the energy storage control modules of the active modules located at the head end and the tail end are connected with the valve control system.
Optionally, in some embodiments, the valve control system includes at least one valve controller, the power control module and the energy storage control module each being in communication with the valve controller.
Optionally, in some embodiments, the valve control system includes two of the valve controllers, a first valve controller and a second valve controller, respectively, the power control module being in communication with the first valve controller and the energy storage control module being in communication with the second valve controller.
Optionally, in some embodiments, the first valve controller and the second valve controller are in communication; and/or
The first valve controller and the second valve controller are different plug-in units arranged in the same device, or the first valve controller and the second valve controller are arranged in different devices; and/or
The first valve controller is configured with a double system for online switching; and/or
The second valve controller configures a dual system for online switching.
Optionally, in some embodiments, the connection switch is controlled by the power control module and/or the energy storage control module; and/or
The connecting switch is connected with a charging loop in parallel, the charging loop comprises a charging switch and a resistor which are connected in series, and the charging switch is controlled by the power control module and/or the energy storage control module.
Optionally, in some embodiments, the energy storage element comprises a battery, a super capacitor, a flywheel energy storage, a gas compression energy storage, or any combination thereof; and/or
The energy storage unit further comprises a DC/DC converter, and the DC/DC converter is arranged between the energy storage element and the input end of the energy storage unit; and/or
The energy storage control module comprises an under-voltage protection unit, wherein when the bypass switch is switched on and the voltage of the energy storage element is lower than a threshold value, the under-voltage protection unit enables the energy storage control module to stop taking energy from the energy storage element; and/or
The energy storage control module samples a position node of the bypass switch.
Correspondingly, the control method applied to the power grid support type active converter comprises an offline self-checking mode, an active starting mode, a black starting mode or any combination of the offline self-checking mode, the active starting mode and the black starting mode; wherein,
the offline self-checking mode comprises the following steps: the energy storage unit is used for supplying energy, so that the self-inspection of the active module is realized, and whether a starting condition is met or not is judged;
the active start-up mode includes: when the alternating current power grid is normal, the power grid support type active converter is connected with the power grid firstly, and then starting operation is realized;
the black start mode includes: when the power grid support type active converter is not connected with a power grid or the power grid loses power, the energy storage unit provides starting energy to realize the operation of the converter and output independent active and/or reactive support power grids.
Optionally, in some embodiments, when the off-line self-test mode, the active start mode, and the black start mode are available at the same time, the off-line self-test mode further includes determining to enter the active start mode or the black start mode according to a grid voltage condition.
Optionally, in some embodiments, the step of offline self-test mode includes:
acquiring position information of the bypass switches of all the power units and the state of charge values of the energy storage elements through the energy storage control module;
entering a first link: judging whether the number of the bypass sub-modules exceeds the allowable redundancy number, if not, entering a second link, and if so, not passing the self-test and not allowing to enter the second link; the bypass sub-module is an active module with a closed bypass switch;
a second ring section: and judging whether the number of the active modules with the state of charge values lower than the operation allowable value exceeds the allowable number, if so, determining that the black start self-test does not pass, and not allowing to enter a black start mode.
Optionally, in some embodiments, the step of the active start mode comprises:
charging the direct current capacitor by an alternating current power grid, wherein the power control module obtains energy from the direct current capacitor;
all the non-bypass sub-modules establish communication with the valve control system; the non-bypass sub-module is an active module with a bypass switch disconnected;
when the state of charge value of the energy storage element is smaller than a threshold value, controlling the power unit correspondingly connected with the energy storage element to output zero level, or limiting the power unit to work in a charging state or a power limiting state;
controlling the power semiconductor devices in the power units to be unlocked, and the grid-connected and unlocked operation of the grid-supported active converter provides active and/or reactive support for a grid;
and controlling to improve the state of charge value of the energy storage element, and when the state of charge value is larger than a threshold value, removing the limitation on the power unit.
Optionally, in some embodiments, the step of the black start mode includes:
the connecting switch is closed, and the direct current capacitor is charged through the energy storage unit;
the power control module is used for obtaining energy from the direct current capacitor;
all the non-bypass sub-modules establish communication with the valve control system; the non-bypass sub-module is an active module with a bypass switch disconnected;
when the state of charge value of the energy storage element is smaller than a threshold value, controlling a power unit correspondingly connected with the energy storage element to output a zero level state;
and controlling a power semiconductor device in the power unit to unlock, and outputting a given voltage by the converter to realize grid connection or island power supply.
Correspondingly, the present application provides a commutation system, including at least one commutation arm, the commutation arm includes at least one said grid-supported active converter.
Optionally, in some embodiments, the converter comprises one of the commutating arms, and the commutating arm is connected across two poles of the dc bus;
or the converter comprises three converter arms, each converter arm is connected in a triangular mode, and the leading-out end of each converter arm is connected with an alternating current bus;
or the converter comprises three converter arms, wherein the converter arms are in star connection, and the leading-out end is connected with an alternating current bus;
or the converter comprises six converter arms, every two converter arms are connected in series to form a group, an end socket led out between the two converter arms in each group is connected with an alternating current bus, the group and the group are mutually connected in parallel, and the end sockets connected in parallel are led out to be connected with two poles of a direct current bus.
Has the advantages that: compared with the prior art, the power grid supporting type active converter of this application has set up the energy storage control module, and this energy storage control module is stable from the energy storage component and is got the energy, and control energy storage unit work to with the communication of valve accuse system, can guarantee when the electric wire netting loses electricity that the energy storage control module of active module still can normally work, realize black start-up function in coordination with power control module: namely, the process of closing the charging contactor, charging the direct current capacitor and unlocking the starting; the communication is still not interrupted when the active module exits operation. The control method of the power grid support type active converter comprises an offline self-checking mode, an active starting mode, a black starting mode or any combination of the offline self-checking mode, the active starting mode and the black starting mode, and different use requirements are fully guaranteed by providing a plurality of selectable modes. The converter system provides guidance for the practical application of the power grid support type active converter.
Drawings
The technical solution and other advantages of the present application will become apparent from the detailed description of the embodiments of the present application with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a grid-supported active converter provided in an embodiment of the present application;
fig. 2 is a schematic diagram of another grid-supported active converter structure provided in an embodiment of the present application;
FIG. 3 is a schematic diagram illustrating a point-to-point connection between an active converter chain and a valve control system according to an embodiment of the present disclosure;
FIG. 4 is a schematic diagram of the head-to-tail connection of the active converter chain and the valve control system in the embodiment of the present application;
FIG. 5 is a schematic diagram illustrating a series random connection of an active converter chain and a valve control system according to an embodiment of the present disclosure;
FIG. 6 is a schematic diagram of the serial connection of the active converter chain and the valve control system in the embodiment of the present application;
fig. 7 is a schematic structural diagram of a combined connection manner of an active converter chain and a valve control system in an embodiment of the present application;
FIG. 8 is a schematic diagram of a connection switch connected in parallel with a charging circuit according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of an application manner of a converter arm composed of a grid-supported active converter provided in an embodiment of the present application;
fig. 10 is a schematic structural diagram of an application manner of three converter arms formed by the grid-supported active converter provided in the embodiment of the present application;
fig. 11 is a schematic structural diagram of another application manner of three converter arms composed of a grid-supported active converter provided in the embodiment of the present application;
fig. 12 is a schematic structural diagram of an application manner of six converter arms composed of a grid-supported active converter provided in an embodiment of the present application;
fig. 13 is a flowchart of a control method of a grid-supported active converter provided in an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the embodiments described are only a few 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.
In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" are to be interpreted broadly, e.g., as being fixed or detachable or integrally connected; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features.
The following disclosure provides many different embodiments or examples for implementing different features of the application. In order to simplify the disclosure of the present application, specific example components and arrangements are described below. Of course, they are merely examples and are not intended to limit the present application.
The applicant finds that for a traditional active converter, when a system is started, as the switching-on of a charging contactor needs to be controlled by a sub-module control unit, the sub-module control unit obtains energy from a sub-module direct-current capacitor, the direct-current capacitor in the sub-module needs to obtain energy from a power grid side, and the energy obtaining cannot be completed under the condition of power grid power loss; therefore, the conventional method can only finish normal starting after the direct-current capacitor is charged by firstly connecting the grid and then closing the charging contact to connect the direct-current capacitor and the energy storage unit. In order to meet the requirement of black start, the applicant improves the conventional scheme to obtain the technical scheme of the application.
As shown in fig. 1, an embodiment of the present application provides a grid-supported active converter, which includes an active converter chain and a valve control system. The active commutation chain mainly comprises active modules 1, the number of the active modules 1 is at least 1, that is, the active commutation chain comprises N active modules 1, and N is an integer greater than or equal to 1. In some embodiments, when N is greater than or equal to 2, the active modules 1 are connected in series.
The active module 1 includes an energy storage unit, a power control module (SMC for short), and an energy storage control module (BCM for short).
The main components of the energy storage unit include at least one energy storage element, that is, in some embodiments, only one energy storage element may be disposed in the energy storage unit, and in some other embodiments, a plurality of energy storage elements may be disposed in the energy storage unit. Alternatively, the energy storage element may take a variety of forms, including a battery, a supercapacitor, flywheel storage, gas compression storage, or any combination thereof. Other devices capable of storing electrical energy may be selected, as are known in the art, and one skilled in the art may select from these devices according to the different needs of the different embodiments.
The power unit includes a dc capacitor and a power component connected in parallel, where the power component includes a full bridge circuit and/or a half bridge circuit formed by power semiconductor devices, that is, the power component may be the full bridge circuit shown in fig. 1, or may be a half bridge circuit or a full bridge and half bridge hybrid circuit known in the art, and a person skilled in the art may select a circuit form of the power component according to different requirements of different embodiments. The direct current capacitor is connected with the energy storage unit through a connecting switch KM, and the alternating current end of the power unit is connected with the bypass switch in parallel.
And the power control module controls the power unit to work and is communicated with the valve control system.
And the energy storage control module is used for acquiring energy from the energy storage element of the energy storage unit and controlling the energy storage unit to work. And the energy storage control module is in communication with the valve control system. Specifically, in some embodiments, an energy storage communication unit is disposed in the energy storage control module, and the energy storage control module communicates with the valve control system through the energy storage communication unit disposed therein.
In addition, the applicant also finds that in the conventional scheme, the sub-module control unit and the valve control unit are in a one-to-one communication mode and do not have communication redundancy capability, once optical fiber communication is interrupted, the module is forced to bypass, the corresponding energy storage unit also quits operation, the energy storage unit has high value and is easy to damage, the operation yield of equipment is influenced after the energy storage unit quits operation, and meanwhile, the State of Charge (SOC) of each sub-module energy storage unit of the converter chain is uneven. Therefore, the applicant further improves the scheme of the present application to achieve communication redundancy.
Specifically, in order to realize that the power control module and the energy storage control module are redundant in communication with each other, in some embodiments, the power control module and the energy storage control module are in communication, the communication mode can be realized in an optical and/or electrical mode, and communication resources are shared through communication between the power control module and the energy storage control module, so that the communication redundancy capability of the system is improved. Or in some embodiments, the power control module and the energy storage control module are integrated together to form a module, and the module has all functions of both the power control module and the energy storage control module, so that the effect of mutual communication redundancy can be achieved without mutual communication. Meanwhile, the power control module and the energy storage control module are communicated with the valve control system, double communication redundancy is realized by combining a communication mode of a double-loop network, any node or communication link in the communication network is interrupted, interruption of data transmission between the systems cannot be caused, and the double-loop network has the advantage of high reliability.
Wherein the power control module receives control commands from the valve control system and/or the energy storage control module. It can be understood that: in some embodiments, the power control module accepts control instructions from the valve control system; in some embodiments, the power control module may be configured to accept control commands from the energy storage control module; in some embodiments, the power control module may be configured to accept control commands from the energy storage control module and the valve management system.
The energy storage control module receives control commands from the valve control system and/or the power control module. It can be understood that: in some embodiments, the energy storage control module may be configured to receive control instructions from the valve control system; in some embodiments, the energy storage control module may be configured to accept control commands from the power control module; in some embodiments, the energy storage control module may be configured to accept control commands from the power control module and the valve control system.
The Valve control system comprises at least one Valve controller (VBC for short), and the power control module and the energy storage control module are communicated with the Valve controller.
Referring to FIG. 1, in some embodiments, the valve control system is provided with two valve controllers, a first valve controller VBC1 and a second valve controller VBC2, a power control module in communication with the first valve controller VBC1, and an energy storage control module in communication with the second valve controller VBC 2.
Referring to fig. 2, in some embodiments, only one valve controller is provided in the valve control system, and both the power control module and the energy storage control module communicate with the same valve controller.
In some embodiments, the valve controllers in the valve control system are all in communication, and the specific communication manner can be realized by adopting an optical and/or electrical communication manner, that is, in the embodiment that two valve controllers are arranged, the communication exists between the first valve controller and the second valve controller, so that the communication redundancy effect can be further enhanced.
The valve controllers in the valve control system may be integrated into the same device, or may be implemented in different devices, and specifically, in some embodiments, the first valve controller and the second valve controller are different inserts disposed in the same device, or in some embodiments, the first valve controller and the second valve controller are disposed in different devices. And, the first valve controller is configured with the A and B dual system capable of switching on line and/or the second valve controller is configured with the A and B dual system capable of switching on line, thereby further improving the reliability of the system.
Further, for some embodiments in which the active converter chain includes a plurality of active modules connected in series with each other (i.e., when N is greater than or equal to 2), in order to enhance the effect of the dual communication redundancy, the connection manner of the active converter chain and the valve control system may be selectively configured, where the selectable connection manner mainly includes a point-to-point connection, a packet end-to-end connection, a series random connection, a series end-to-end connection, or any combination thereof.
Specifically, as shown in fig. 3, the point-to-point connection is: in the active converter chain, all the active modules are connected with a valve control system through respective power control modules and/or energy storage control modules. In the connection mode, each active module is independently connected with the valve control system, in the embodiment which generally adopts the connection mode, the power control module and the energy storage control module are mutually in communication redundancy, and even if the link connection between either of the power control module and the energy storage control module and the valve control system is interrupted, the communication can be maintained through the other one, so that the stability of the communication is ensured.
As shown in fig. 4, the packet end-to-end connection is: in the active commutation chain, P active modules are taken as a group, and P is more than or equal to 2 and less than or equal to N; in each group, the active modules are connected in series through the power control module and/or the energy storage control module, and the power control modules and/or the energy storage control modules of the active modules positioned at the head end and the tail end are connected with the valve control system. In the connection mode, each active module in each group is provided with at least two links for maintaining communication with the valve control system, and even if one link is interrupted, the other link can still keep the communication smooth. In the embodiment shown in fig. 4, N is 6 and P is 2.
As shown in fig. 5, the series random connection is: in the active converter chain, all active modules are connected in series through power control modules and/or energy storage control modules, M active modules are selected optionally, M is more than or equal to 2 and less than or equal to N, and the active modules are connected with a valve control system through the power control modules and/or the energy storage control modules. In the connection mode, each active module is provided with at least two links for maintaining communication with the valve control system, some active modules selected to be connected with the valve control system and even at least three communication links for maintaining communication with the valve control system, so that other links can maintain communication even if one node is interrupted. In the embodiment shown in fig. 5, N is 6 and M is 6.
As shown in fig. 6, the series connection end-to-end is: in the active current conversion chain, all active modules are connected in series through power control modules and/or energy storage control modules, and the power control modules and/or the energy storage control modules of the active modules positioned at the head end and the tail end are connected with a valve control system. In the connection mode, each active module is provided with at least two links for maintaining the communication with the valve control system, and even if one link is interrupted, the other link can still keep the communication smooth.
In particular, when N is 2, N is P is M is 2, and in this case, the end result of the three connection modes, i.e., the end-to-end connection of the packets, the random connection of the series, and the end-to-end connection of the series, is the same.
In any of the above manners, the power control module and the energy storage control module may be configured to communicate with each other, so that the two modules are redundant in communication, and it is expected that the possibility of communication interruption is further reduced to be extremely low, and the stability of data transmission can be ensured.
In some embodiments, the connection manner between the active converter chain and the valve control system may be a combined connection manner, for example, a combined connection manner of grouped end-to-end connection and serial end-to-end connection may be selected, specifically, referring to the power grid support type active converter shown in fig. 7, power control modules of K active modules are selected to be connected in series, the ends of the power control modules are respectively communicated with the valve control system, and K is greater than or equal to 2 and less than or equal to N; the power control module inside the active module is communicated with the energy storage communication unit; the energy storage communication units of the L active modules are connected in series, the heads and the tails of the energy storage communication units are respectively communicated with the valve control system, and L is more than or equal to 2 and less than or equal to N. Fig. 7 shows an embodiment when K is 3 and L is 6, where the power control module and the energy storage communication unit form a dual-ring network connection mode, so as to sufficiently ensure stability of data transmission. Of course, depending on the number of active modules, K and L may be chosen to have other values, for example, K2, L3; alternatively, other combinations of connections may be used.
The connecting switch KM is connected between the direct current capacitor and the energy storage unit and can be controlled by the power control module and/or the energy storage control module. As shown in fig. 8, in some embodiments, the connection switch is connected in parallel with a charging circuit, and the charging circuit includes a charging switch and a resistor connected in series, and the charging switch is controlled by the power control module and/or the energy storage control module. Through setting up the charging circuit, when energy storage unit and direct current capacitor are connected, reduce impulse current.
In some embodiments, the energy storage unit further comprises a DC/DC converter, and the DC/DC converter is disposed between the energy storage element and the input terminal of the energy storage unit to perform isolation and voltage conversion.
In some embodiments, the grid-supported active converter further includes an under-voltage protection unit, and when the bypass switch is switched on and the voltage of the energy storage element is lower than a threshold value, the energy storage control module stops taking energy from the energy storage element through the under-voltage protection unit.
In some embodiments, the position node of the bypass switch may be sampled by the energy storage control module.
Correspondingly, an embodiment of the present application further provides a converter system, where the above-mentioned grid-supported active converter is applied to the converter system, and specifically, the converter system includes at least one converter arm, each converter arm includes i grid-supported active converters, and i is an integer greater than or equal to 1. On the premise of not departing from the inventive concept of the present application, the structure of the grid-supported active converter is set as required. Taking the converter in fig. 7 as an example, the power control modules of K active modules are connected in series and are respectively communicated with the valve control system from beginning to end, and K is greater than or equal to 2 and less than or equal to i × N; the power control module inside the active module is communicated with the energy storage communication unit; the energy storage communication units of the L active modules are connected in series, the heads and the tails of the energy storage communication units are respectively communicated with the valve control system, and L is more than or equal to 2 and less than or equal to i × N.
In some embodiments, when one of the commutating arms is provided, the commutating arm is connected across two poles of the dc bus, as shown in fig. 9, and this structure is suitable for a high-voltage dc direct-hanging energy storage system.
In some embodiments, when three of the commutation arms are provided, the commutation arms may be connected in a delta shape, and the leading end is connected to an ac bus; alternatively, as shown in fig. 11, three converter arms may be star-connected and terminated with an ac bus, which is a common configuration for static var generators.
As shown in fig. 12, six of the commutation arms may be provided, each two of the commutation arms are connected in series to form a group, an ac bus is connected to a terminal led out between the two commutation arms in each group, the groups are connected in parallel with each other, and the terminals connected in parallel are led out to connect two poles of a dc bus.
Correspondingly, the embodiment of the application also provides a control method suitable for the above power grid support type active converter, and the method includes an offline self-test mode, an active start mode, a black start mode, or any combination thereof.
Wherein, the off-line self-checking mode comprises: and the energy storage unit supplies energy, so that the self-inspection of the active module is realized, and whether a starting condition is met or not is judged.
Wherein the active start-up mode comprises: when the alternating current power grid is normal, the power grid supporting type active converter is connected with the power grid firstly, and then starting operation is achieved.
Wherein the black start mode includes: when the power grid support type active converter is not connected with a power grid or the power grid loses power, the energy storage unit provides starting energy to realize the operation of the converter and output independent active and reactive support power grids.
In some embodiments, when the off-line self-test mode, the active start mode and the black start mode are provided, the off-line self-test mode further includes determining to enter the active start mode or the black start mode according to a grid voltage condition.
Specifically, as shown in fig. 13, in some embodiments, the control method includes a step of performing an offline self-test mode, where the offline self-test mode includes:
the position information of bypass switches of all power units and the charge state values of energy storage elements are obtained through an energy storage control module;
entering a first link: judging whether the number of the bypass sub-modules exceeds the allowable redundancy number, if not, entering a second link, and if so, not passing the self-test and not allowing to enter the second link; the bypass sub-module is an active module with a closed bypass switch;
a second ring section: and judging whether the number of the active modules with the state of charge values lower than the operation allowable value exceeds the allowable number, if so, determining that the black start self-test does not pass, and not allowing to enter a black start mode.
When the self-checking passes, judge whether there is alternating current power supply, when alternating current power supply, alternating current power grid is in normal condition, enters active start mode, and active start mode's step includes:
charging the direct current capacitor by the alternating current power grid, and taking energy from the direct current capacitor by the power control module;
all the non-bypass sub-modules establish communication with the valve control system; the non-bypass sub-module is an active module with a bypass switch disconnected;
when the state of charge value of the energy storage element is smaller than a threshold value, controlling a power unit correspondingly connected with the energy storage element to output a zero level, or limiting the power unit to work in a charging state or a power limiting state;
controlling a power semiconductor device in a power unit to be unlocked, and controlling a power grid supporting type active converter to be in grid-connected unlocking operation to provide active and/or reactive support for a power grid;
and controlling to improve the state of charge value of the energy storage element, and removing the limitation on the power unit when the state of charge value is larger than a threshold value.
When the self-checking passes, judge whether there is alternating current power supply, when no alternating current power supply, enter black start mode, black start mode's step includes:
the connecting switch is closed, and the direct current capacitor is charged through the energy storage unit;
the power control module obtains energy from the direct current capacitor;
all the non-bypass sub-modules establish communication with the valve control system; the non-bypass sub-module is an active module with a bypass switch disconnected;
when the charge state value of the energy storage element is smaller than a threshold value, controlling a power unit correspondingly connected with the energy storage element to output a zero level state;
and controlling a power semiconductor device in the power unit to unlock, and outputting a given voltage by the converter to realize grid connection or island power supply.
The above detailed description is given to a power grid support type active converter, a control method thereof and a converter system provided by the embodiments of the present application, and a specific example is applied in the present application to explain the principle and the implementation manner of the present application, and the description of the above embodiments is only used to help understanding the technical scheme and the core idea of the present application; those of ordinary skill in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications or substitutions do not depart from the spirit and scope of the present disclosure as defined by the appended claims.
Claims (15)
1. A power grid support type active converter is characterized by comprising an active converter chain and a valve control system; wherein the active commutation chain comprises at least one active module, the active module comprising:
an energy storage unit comprising at least one energy storage element;
the power unit comprises a direct current capacitor and a power assembly which are connected in parallel, the power assembly comprises a full-bridge circuit and/or a half-bridge circuit formed by power semiconductor devices, the direct current capacitor is connected with the energy storage unit through a connecting switch, and an alternating current end of the power unit is connected with a bypass switch in parallel;
the power control module controls the power unit to work;
the energy storage control module is used for acquiring energy from the energy storage element and controlling the energy storage unit to work;
the valve control system is in communication with the energy storage control module and the power control module.
2. The grid supported active converter according to claim 1, wherein the power control module is in communication with the energy storage control module or is integrated with the energy storage control module.
3. The grid-supported active converter according to claim 1, wherein the active converter chain comprises N active modules connected in series, N being an integer greater than or equal to 2;
the connection mode of the active current conversion chain and the valve control system comprises point-to-point connection, grouping head-to-tail connection, series random connection, series head-to-tail connection or any combination thereof; wherein,
the point-to-point connection is: in the active converter chain, all the active modules are connected with the valve control system through the respective power control module and/or the energy storage control module;
the grouping head-to-tail connection is as follows: in the active commutation chain, P active modules are in a group, and P is more than or equal to 2 and less than or equal to N; in the group, the active modules are connected in series through the power control module and/or the energy storage control module, and the power control modules and/or the energy storage control modules of the active modules at the head end and the tail end are connected with the valve control system;
the series random connection is: in the active converter chain, all the active modules are connected in series through the power control module and/or the energy storage control module, M active modules are selected optionally, M is more than or equal to 2 and less than or equal to N, and the active modules are connected with the valve control system through the power control module and/or the energy storage control module of the M active modules;
the serial connection end-to-end connection is as follows: in the active commutation chain, all the active modules are connected in series through the power control module and/or the energy storage control module, and the power control modules and/or the energy storage control modules of the active modules located at the head end and the tail end are connected with the valve control system.
4. The grid supported active converter of claim 1, wherein the valve control system comprises at least one valve controller, the power control module and the energy storage control module each being in communication with the valve controller.
5. The grid supported active converter of claim 4, wherein the valve control system comprises two valve controllers, a first valve controller and a second valve controller, the power control module being in communication with the first valve controller and the energy storage control module being in communication with the second valve controller.
6. The grid supported active converter of claim 5, wherein the first valve controller and the second valve controller are in communication; and/or
The first valve controller and the second valve controller are different plug-in units arranged in the same device, or the first valve controller and the second valve controller are arranged in different devices; and/or
The first valve controller is configured with a double system for online switching; and/or
The second valve controller configures a dual system for online switching.
7. The grid supported active converter according to claim 1, wherein the connection switches are controlled by the power control module and/or the energy storage control module; and/or
The connecting switch is connected with a charging loop in parallel, the charging loop comprises a charging switch and a resistor which are connected in series, and the charging switch is controlled by the power control module and/or the energy storage control module.
8. The grid supported active converter according to claim 1, wherein the energy storage element comprises a battery, a super capacitor, flywheel energy storage, gas compression energy storage, or any combination thereof; and/or
The energy storage unit further comprises a DC/DC converter, and the DC/DC converter is arranged between the energy storage element and the input end of the energy storage unit; and/or
The energy storage control module comprises an under-voltage protection unit, wherein when the bypass switch is switched on and the voltage of the energy storage element is lower than a threshold value, the under-voltage protection unit enables the energy storage control module to stop taking energy from the energy storage element; and/or
The energy storage control module samples a position node of the bypass switch.
9. A method for controlling a grid supported active converter according to any of claims 1-8, comprising an offline self-test mode, an active start-up mode, a black start-up mode or any combination thereof; wherein,
the offline self-checking mode comprises the following steps: the energy storage unit is used for supplying energy, so that the self-inspection of the active module is realized, and whether a starting condition is met or not is judged;
the active start-up mode includes: when the alternating current power grid is normal, the power grid support type active converter is connected with the power grid firstly, and then starting operation is realized;
the black start mode includes: when the power grid support type active converter is not connected with a power grid or the power grid loses power, the energy storage unit provides starting energy to realize the operation of the converter and output independent active and/or reactive support power grids.
10. The method as claimed in claim 9, wherein when there are an offline self-test mode, an active start mode and a black start mode, the offline self-test mode further comprises determining to enter the active start mode or the black start mode according to the grid voltage condition.
11. A method of controlling a grid supported active converter according to claim 9, wherein the step of performing an offline self-test mode comprises:
acquiring position information of the bypass switches of all the power units and the state of charge values of the energy storage elements through the energy storage control module;
entering a first link: judging whether the number of the bypass sub-modules exceeds the allowable redundancy number, if not, entering a second link, and if so, not passing the self-test and not allowing to enter the second link; the bypass sub-module is an active module with a closed bypass switch;
a second ring section: and judging whether the number of the active modules with the state of charge values lower than the operation allowable value exceeds the allowable number, if so, determining that the black start self-test does not pass, and not allowing to enter a black start mode.
12. A method of controlling a grid supported active converter according to claim 9, wherein the step of active start-up mode comprises:
charging the direct current capacitor by an alternating current power grid, wherein the power control module obtains energy from the direct current capacitor;
all the non-bypass sub-modules establish communication with the valve control system; the non-bypass sub-module is an active module with a bypass switch disconnected;
when the state of charge value of the energy storage element is smaller than a threshold value, controlling the power unit correspondingly connected with the energy storage element to output zero level, or limiting the power unit to work in a charging state or a power limiting state;
controlling the power semiconductor devices in the power units to be unlocked, and the grid-connected and unlocked operation of the grid-supported active converter provides active and/or reactive support for a grid;
and controlling to improve the state of charge value of the energy storage element, and when the state of charge value is larger than a threshold value, removing the limitation on the power unit.
13. The method of controlling a grid supported active converter according to claim 9, wherein the step of the black start mode comprises:
the connecting switch is closed, and the direct current capacitor is charged through the energy storage unit;
the power control module is used for obtaining energy from the direct current capacitor;
all the non-bypass sub-modules establish communication with the valve control system; the non-bypass sub-module is an active module with a bypass switch disconnected;
when the state of charge value of the energy storage element is smaller than a threshold value, controlling a power unit correspondingly connected with the energy storage element to output a zero level state;
and controlling a power semiconductor device in the power unit to unlock, and outputting a given voltage by the converter to realize grid connection or island power supply.
14. A converter system comprising at least one converter arm comprising at least one grid supported active converter according to claims 1-8.
15. The commutation system of claim 14, comprising one of the commutation arms connected across both poles of a dc bus;
or the converter comprises three converter arms, each converter arm is connected in a triangular mode, and the leading-out end of each converter arm is connected with an alternating current bus;
or the converter comprises three converter arms, wherein the converter arms are in star connection, and the leading-out end is connected with an alternating current bus;
or the converter comprises six converter arms, every two converter arms are connected in series to form a group, an end socket led out between the two converter arms in each group is connected with an alternating current bus, the group and the group are mutually connected in parallel, and the end sockets connected in parallel are led out to be connected with two poles of a direct current bus.
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