CN115224739A - New energy island power grid system of sending out through flexible direct current overhead line - Google Patents
New energy island power grid system of sending out through flexible direct current overhead line Download PDFInfo
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- CN115224739A CN115224739A CN202211048291.2A CN202211048291A CN115224739A CN 115224739 A CN115224739 A CN 115224739A CN 202211048291 A CN202211048291 A CN 202211048291A CN 115224739 A CN115224739 A CN 115224739A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/14—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by switching loads on to, or off from, network, e.g. progressively balanced loading
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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
- 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
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
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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
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/28—The renewable source being wind energy
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/40—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously
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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]
Abstract
The invention discloses a new energy island power grid sending-out system through a flexible direct current overhead line, which adopts a bipolar direct current framework to improve the flexibility and the reliability of the operation of the system, an energy storage device is used for inhibiting the intermittent characteristic and the fluctuation characteristic of new energy, an alternating current energy consumption device at a sending end is coordinated and matched with a flexible direct current converter at the sending end and a new energy unit to realize the consumption of surplus power of power at the sending end, the same outer ring controller is applied to a double closed-loop control system with double poles at the sending end, the possible shelf-off phenomenon of double pole voltage frequency control at the sending end can be avoided, a flexible direct current converter station at a receiving end adopts a fixed direct current voltage control strategy and a fixed active power control strategy, and the self-clearing of direct current faults of the new energy island power grid sending-out system through the flexible direct current overhead line is realized by controlling and cutting off fault currents when a direct current line fails, and the technical problems that the coordinated control of new energy and flexible direct current is difficult, the surplus power influences the stable operation of the system and the faults at the direct current side cannot be cleared by self-clearing are solved.
Description
Technical Field
The invention relates to the technical field of flexible direct current transmission, in particular to a system for sending a new energy island power grid out through a flexible direct current overhead line.
Background
Most new energy bases are built in remote areas, the load level is low, the grid structure is weak, and the requirements for stable delivery of new energy islands are obvious. The flexible direct current transmission has the characteristics of flexibility, controllability, high efficiency and the like, and is one of important power transmission means for new energy transmission. For a sending end, the flexible direct current converter can provide stable alternating voltage for a new energy electric field, can operate in an isolated island mode, can sufficiently and quickly dynamically compensate, reduces the risk of the new energy unit being disconnected from the network, and improves the utilization rate of new energy. For a receiving end, the flexible direct current has no problem of phase commutation failure, dynamic reactive compensation can be provided, and the method has important significance for effectively solving the problems of stability of a multi-direct-current feed-in alternating current power grid, resistance to serious faults of the power grid and the like.
When the true bipolar flexible dc power transmission system is applied to a situation where new energy is sent out through an overhead line, the following problems still need to be solved: 1) The coordination control problem of new energy and flexible direct current and the bipolar coordination control problem of a sending end; 2) Under the disturbance of serious alternating current fault, emergency locking of a converter valve and the like, the surplus power of a direct current system and the large fluctuation of direct current voltage and current are easily caused, and the stable operation of the system is seriously influenced; 3) When the direct current fault occurs, a mode of rapidly cutting off direct current needs to be adopted, electric arcs generated by flashover are rapidly extinguished, and the fault is rapidly cleared.
Disclosure of Invention
The invention provides a new energy island power grid system for sending out through a flexible direct current overhead line, which is used for solving the technical problems that the coordination control of new energy and flexible direct current is difficult, the stable operation of the system is influenced by surplus power, and faults on a direct current side cannot be cleared automatically.
In view of the above, the first aspect of the present invention provides a system for sending a new energy island power grid out through a flexible dc overhead line, including a new energy electric field, a sending-end flexible dc converter station, a receiving-end flexible dc converter station, a bipolar dc overhead line, an energy storage device, and an ac energy consumption device;
the transmission end flexible direct current converter station comprises a transmission end boosting converter transformer and a transmission end flexible direct current converter, the new energy electric field is commonly connected to the transmission end boosting converter transformer through a three-phase alternating current bus, and the transmission end boosting converter transformer is connected with the transmission end flexible direct current converter;
the number of the sending end flexible direct current converter stations is multiple, and the multiple sending end flexible direct current converter stations are connected in parallel;
the receiving end flexible direct current converter station comprises a receiving end converter transformer and a receiving end flexible direct current converter, and the receiving end flexible direct current converter is connected with the receiving end converter transformer;
the sending end flexible direct current converter is connected with the receiving end flexible direct current converter through a bipolar direct current overhead line;
the alternating current energy consumption device and the energy storage device are connected between the new energy electric field and the sending end converter station;
all sending end flexible direct current converter stations adopt a double-closed-loop constant alternating current voltage and frequency control strategy, only one receiving end flexible direct current converter station adopts a constant direct current voltage control strategy, the other receiving end flexible direct current converter stations adopt a constant active power control strategy, and bipolar control in the double-closed-loop constant alternating current voltage and frequency control strategy of the sending end flexible direct current converter stations adopts the same outer loop controller.
Optionally, the system further comprises a direct current energy consumption device;
and the direct current energy consumption device is connected to a direct current outlet of the receiving-end flexible direct current converter.
Optionally, the dc energy dissipation device is formed by a series-connected IGBT device.
Optionally, the configuration group number of the ac energy consuming devices is calculated according to a preset formula, where the preset formula is:
wherein delta is 1 or 2,N Number of AC energy consuming devices Number of sets, P, for AC energy consuming devices Sending end bipolar power Active power, P, for the transmitting-end flexible DC converter Capacity of each group of ac energy consuming devices The capacity of each group of alternating current energy consumption devices.
Optionally, each group of ac energy consuming devices is formed by star-connected IGBT devices connected in series with resistors.
Optionally, the transmitting end boost converter transformer and the receiving end converter transformer are delta/Y0 double-winding transformers or Y/Y0 double-winding transformers or three-winding transformers.
Optionally, the bipolar direct-current overhead line and the sending-end flexible direct-current converter, and the bipolar direct-current overhead line and the receiving-end flexible direct-current converter are connected through smoothing reactors.
Optionally, the number of the receiving end flexible direct current converter stations is one or more than two.
Optionally, the sending-end flexible direct current converter and the receiving-end flexible direct current converter both adopt a single-valve-group form or a double-valve-group series-connection form, each valve group is of a three-phase six-bridge-arm structure, each bridge arm is formed by connecting a plurality of power modules and a bridge arm reactor in series, and each power module adopts a full-bridge submodule or a module mixed with a half-bridge submodule.
Optionally, the transmitting-end flexible dc converter and the receiving-end flexible dc converter of each pole are each formed by connecting more than two flexible dc converters in series.
According to the technical scheme, the new energy island power grid sending system through the flexible direct current overhead line has the following advantages:
the new energy island power grid is sent out of the system through the flexible direct current overhead line, a bipolar direct current framework is adopted, the flexibility and the reliability of the operation of the system are improved, the stable operation of a sending end island system can be maintained by a normal pole even after a single-pole fault is finally locked, an energy storage device is used for inhibiting the intermittent characteristic and the fluctuation characteristic of new energy, part of energy is stored when a new energy field station generates more power, the stored energy is released when the new energy field station generates less power, direct current power transmission is maintained as much as possible, the frequent starting and stopping of direct current are avoided, the system scheduling and the operation maintenance are facilitated, the coordination of an alternating current energy consumption device at the sending end, a sending end flexible direct current converter and a new energy source unit realizes the consumption of surplus power of the sending end power, the same outer ring controller is applied to a sending end bipolar double closed ring control system, the possibility of the frame breaking phenomenon of sending end bipolar voltage frequency control can be avoided, only one fixed direct current voltage control strategy is adopted in a receiving end flexible direct current conversion station, the stable direct current conversion control strategy is adopted, the problem that the surplus current fault can not be removed through the flexible direct current conversion control circuit when the new energy field fault is finally solved, and the fault of the flexible direct current conversion system is eliminated, and the problem that the fault of the fault can not be solved through the flexible direct current conversion system is solved.
Meanwhile, a direct current energy consumption device is arranged at a direct current outlet on the side of the receiving-end flexible direct current converter station and is in coordination with the receiving-end flexible direct current converter for dissipating direct current power which cannot be sent out by a direct current side fault when the receiving end alternating current fault occurs, and the phenomenon of overcurrent and overvoltage caused by the fact that the direct current surplus power continuously charges a bridge arm submodule of the receiving-end flexible direct current converter station is avoided.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is an architecture diagram of a system for sending a new energy island power grid out through a flexible dc overhead line according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a single-converter overhead line delivery system of a new energy island grid provided in an embodiment of the present invention, the system being delivered via a flexible dc overhead line;
fig. 3 is a schematic diagram of a dual-converter overhead line transmission system of a new energy island power grid transmission system via a flexible dc overhead line transmission system according to an embodiment of the present invention;
fig. 4 is a schematic diagram of another double-converter overhead line transmission system of the new energy island grid transmission system through a flexible dc overhead line transmission system according to the embodiment of the present invention;
fig. 5 is a schematic structural diagram of a flexible dc converter (modular multilevel converter) of a new energy island power grid sent out of a system through a flexible dc overhead line according to an embodiment of the present invention;
fig. 6 is a circuit diagram of a full-bridge sub-module and a half-bridge sub-module provided in the embodiment of the present invention;
fig. 7 is a schematic diagram of double closed loop VF control of a sending-end converter station provided in the embodiment of the present invention;
fig. 8 is a schematic diagram of double closed-loop control of the receiving end converter station provided in the embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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 invention.
For convenience of understanding, please refer to fig. 1, the present invention provides an embodiment of a system for sending a new energy island grid out of a system through a flexible dc overhead line, including a new energy electric field, a sending end flexible dc converter station, a receiving end flexible dc converter station, a bipolar dc overhead line, an energy storage device, and an ac energy consumption device;
the transmission end flexible direct current converter station comprises a transmission end boosting converter transformer and a transmission end flexible direct current converter, the new energy electric field is commonly connected to the transmission end boosting converter transformer through a three-phase alternating current bus, and the transmission end boosting converter transformer is connected with the transmission end flexible direct current converter;
the number of the sending end flexible direct current converter stations is two, and the two sending end flexible direct current converter stations are connected in parallel;
the receiving end flexible direct current converter station comprises a receiving end converter transformer and a receiving end flexible direct current converter, and the receiving end flexible direct current converter is connected with the receiving end converter transformer;
the sending end flexible direct current converter is connected with the receiving end flexible direct current converter through a bipolar direct current overhead line;
the alternating current energy consumption device and the energy storage device are connected between the new energy electric field and the sending end converter station;
all sending end flexible direct current converter stations adopt a double-closed-loop constant alternating current voltage and frequency control strategy, only one receiving end flexible direct current converter station adopts a constant direct current voltage control strategy, the other receiving end flexible direct current converter stations adopt a constant active power control strategy, and bipolar control in the double-closed-loop constant alternating current voltage and frequency control strategy of the sending end flexible direct current converter stations adopts the same outer loop controller.
It should be noted that the new energy island power grid built in the embodiment of the present invention is sent out of the system through the flexible dc overhead line, as shown in fig. 1, and includes a new energy electric field, a sending-end flexible dc converter station, a receiving-end flexible dc converter station, a bipolar dc overhead line, and an ac energy consumption device. The new energy electric field comprises a wind power plant, a photovoltaic electric field and other renewable energy electric fields. The direct-current overhead line is adopted, the structure is simple, the line cost is low, the corridor utilization rate is high, the running loss is small, the maintenance is convenient, and the distance and the capacity of new energy delivery are improved. The sending-end flexible direct current converter station comprises a sending-end boosting converter transformer and a sending-end flexible direct current converter, the sending-end flexible direct current converter is grounded, the new energy electric field is connected to the sending-end boosting converter transformer through a three-phase alternating current bus, and the sending-end boosting converter transformer is connected with the sending-end flexible direct current converter. The sending end flexible direct current converter can adopt a single valve bank form or a double valve bank series form, each valve bank is of a three-phase six-bridge arm structure, and each bridge arm is formed by connecting a plurality of power modules and a bridge arm reactor in series (as shown in fig. 5). The power module adopts a full-bridge sub-module (as shown in a full-bridge circuit structure shown in fig. 6, the power module is composed of four turn-off fully-controlled switching devices, four anti-parallel diodes and an energy storage capacitor, and can output three levels of a positive level, a negative level and a zero level) or a module which is formed by mixing a full-bridge sub-module and a half-bridge sub-module (as shown in a half-bridge circuit structure shown in fig. 6, the power module is composed of two turn-off fully-controlled switching devices, two anti-parallel diodes and an energy storage capacitor, and can output two levels of a positive level and a zero level). When the flexible direct current converter is formed by mixing a full-bridge submodule topology and a half-bridge submodule topology, namely, a bridge arm has a certain number of full-bridge submodules and a certain number of half-bridge submodules, the manufacturing cost and the cost of the flexible direct current converter can be further reduced under the condition of meeting the requirement of direct current voltage regulation. The transmitting end flexible direct current converter is mainly connected with a transmitting end boosting converter transformer and connected with a receiving end flexible direct current converting station through a bipolar direct current overhead line. And the transmitting end boost converter transformer collects and boosts the electric energy of the connected new energy electric field, and the alternating current subjected to voltage transformation processing is rectified by the transmitting end flexible direct current converter to obtain direct current which is transmitted to the receiving end flexible direct current converter station. The receiving-end flexible direct current converter station comprises a receiving-end converter transformer and a receiving-end flexible direct current converter, the receiving-end flexible direct current converter is grounded, the receiving-end flexible direct current converter can be in a single-valve-set form or a double-valve-set series form, each valve set is of a three-phase six-bridge-arm structure, and each bridge arm is formed by connecting a plurality of power modules and a bridge arm reactor in series (as shown in fig. 5). The power module employs a full-bridge sub-module (as shown in the full-bridge circuit configuration shown in fig. 6) or a module employing a mixture of full-bridge and half-bridge sub-modules (as shown in the half-bridge circuit configuration shown in fig. 6). And the receiving end converter transformer transforms the received alternating current and outputs the transformed alternating current.
The plurality of sending end flexible direct current converter stations can be connected in parallel, namely the sending end flexible direct current converter stations are built in a station, and the sending end flexible direct current converter stations can also be built in different places. The sending end flexible direct current convertor stations adopt a constant alternating Voltage and Frequency (VF) control strategy to provide alternating voltage and frequency required by work for respective new energy electric fields. The VF adopts a vector control framework, namely active component and reactive component control is carried out on the flexible direct current unit under a synchronous rotating coordinate system, and the structure is divided into outer ring control and inner ring control, wherein d-axis voltage outer ring control is used for controlling d-axis component of alternating voltage, and q-axis voltage outer ring control is used for controlling q-axis component of the alternating voltage. The inner loop control comprises active current control and reactive current control, and the inner loop control mainly receives reference values of active current and reactive current from the outer loop control, quickly tracks the reference current and realizes direct control of the amplitude and phase of the alternating-current side voltage of the valve bank. Because the whole system is a bipolar system, in order to avoid a frame-hitting phenomenon which may occur when the fixed alternating Voltage and Frequency (VF) of the sending end are controlled, the double closed-loop control system of the sending end bipolar should adopt the same outer-loop controller, such as a d-axis voltage controller and a q-axis voltage controller shown in fig. 7, the active current controllers of the four poles of the two converter stations of the sending end all adopt the output of the same d-axis voltage controller as the input, and the reactive current controllers of the four poles of the two converter stations of the sending end all adopt the output of the same q-axis voltage controller as the input, so as to realize that the two converter stations cooperatively control the alternating voltage of the sending end. Each pole of the sending end converter station detects the direct current flowing out of the pole in real time, if the direct current flowing out of the pole is increased, the pole of the sending end converter station automatically reduces the bias amount of the direct current voltage through a direct current controller, the number of sub-modules input to the direct current side is reduced, direct control over the direct current voltage is achieved, negative direct current voltage is output, and direct current faults are cleared actively. The process is completely automatically controlled, does not depend on the detection of the protection on the fault, can quickly clear the direct current fault, and can effectively avoid the influence of protection misoperation or refusal.
The number of the receiving-end flexible direct current converter stations can be one or more than two, single-drop-point or multi-drop-point power receiving is achieved, only one of the receiving-end flexible direct current converter stations adopts a fixed direct current voltage control strategy to provide stable direct current voltage for a direct current system, the other receiving-end flexible direct current converter stations all adopt a fixed active power control strategy, and a control framework is shown in fig. 8. The receiving end basic control is that a vector control framework is adopted, active and reactive control is carried out on the flexible direct current unit under a synchronous rotation coordinate system, the structure is divided into outer ring control and inner ring control, wherein the outer ring control comprises active control (active power control and direct current voltage control) and reactive control (reactive power control and alternating current voltage control), and the inner ring control comprises active current control and reactive current control. The inner loop control comprises active current control and reactive current control, and is mainly used for receiving reference values of active current and reactive current from the outer loop control, quickly tracking the reference current and realizing direct control of the amplitude and phase of the alternating-current side voltage of the valve group. Each pole of the receiving end converter station detects the direct current flowing into the pole in real time, if the receiving end converter station detects that the direct current flowing into the pole is reduced and increased reversely, the pole of the receiving end converter station automatically reduces the bias amount of the direct current voltage through the direct current controller, reduces the number of sub-modules input at the direct current side, directly controls the direct current voltage, outputs the negative direct current voltage, and actively clears the direct current fault. The process is completely automatic control, does not depend on protection to detect faults, and can quickly clear direct current faults.
In one embodiment, the bipolar direct current overhead line is connected with the transmitting end flexible direct current converter station and the receiving end flexible direct current converter station through smoothing reactors, and the smoothing reactors are mainly used for smoothing direct current.
In one embodiment, a direct current energy consumption device is arranged at a direct current outlet of the receiving-end flexible direct current converter and used for dissipating direct current power sent out by a direct current side when the receiving end alternating current fails, and the phenomenon of overcurrent and overvoltage caused by continuous charging of a bridge arm submodule by direct current surplus power is avoided. The direct current energy consumption device is formed by connecting a resistor in series with an IGBT device, and the capacity of the direct current energy consumption device is the rated capacity of the receiving end converter station.
In one embodiment, the ac energy consuming device is formed by a star-connected series-connected IGBT device. In order to facilitate operation and maintenance, the alternating current energy consumption devices should be configured redundantly, namely 1 group or 2 groups are configured, the number of the configured groups of the alternating current energy consumption devices is calculated according to a preset formula, and the preset formula is as follows:
wherein delta is 1 or 2,N Number of AC energy consuming devices Number of sets, P, for AC energy consuming devices Sending end bipolar power Active power, P, for the transmitting-end flexible DC converter Capacity of each group of ac energy consuming devices The capacity of each group of alternating current energy consumption devices.
In one embodiment, the sending side boost converter transformer and the receiving side converter transformer are delta/Y0 bifilar transformers or Y/Y0 bifilar transformers (as shown in FIGS. 2 and 3) or three-winding transformers (as shown in FIG. 4). As shown in fig. 2, the flexible dc converters at the transmitting end and the receiving end of each pole are formed by a single flexible dc converter. The operation mode is simple and flexible, and the system reliability is high. As shown in fig. 3, the flexible dc converter at the transmitting end and the receiving end of each pole is formed by connecting two flexible dc converters in series, so that the requirement on the current capacity of the flexible dc converter can be reduced, and the manufacturing difficulty and the manufacturing cost of the flexible dc converter can be reduced. It is understood that in other embodiments, the flexible dc converters at the transmitting end and the receiving end of each pole may also be formed by connecting a plurality of flexible dc converters in series, so as to further improve the voltage level of the flexible dc.
The new energy island power grid provided by the embodiment of the invention is sent out of the system through a flexible direct current overhead line, a bipolar direct current framework is adopted, the flexibility and the reliability of the operation of the system are improved, the stable operation of a sending end island system can be maintained by a normal pole even after a single-pole fault is finally locked, an energy storage device is used for inhibiting the intermittent characteristic and the fluctuation characteristic of new energy, part of energy is stored when a new energy field station generates more power, the stored energy is released when the new energy field station generates less power, direct current power transmission is maintained as much as possible, the frequent starting and stopping of direct current are avoided, the system scheduling and operation maintenance are convenient, the coordination of an alternating current energy consumption device at the sending end, a sending end flexible direct current converter and a new energy source unit realizes the consumption of sending end power and residual power, the same outer ring controller is applied to a sending end bipolar double closed ring control system, the possibility of the occurrence of the direct current frequency control and the frame breaking phenomenon of sending end bipolar voltage frequency control can be avoided, only one fixed direct current voltage control strategy is adopted in a receiving end flexible direct current station, the stable direct current control strategy is adopted, the problem that the residual current fault can not be removed through a flexible direct current conversion control circuit when the new energy field fault is finally solved, and the fault is removed through the flexible direct current control circuit.
Meanwhile, the new energy island power grid provided by the embodiment of the invention is sent out of the system through the flexible direct current overhead line, the direct current energy consumption device is arranged at the direct current outlet at the side of the receiving-end flexible direct current converter station, and the direct current energy consumption device is in coordination with the receiving-end flexible direct current converter and is used for dissipating direct current power which cannot be sent out due to direct current side faults when the receiving-end alternating current faults occur, so that the phenomenon of overcurrent and overvoltage caused by continuous charging of direct current surplus power on a bridge arm submodule of the receiving-end flexible direct current converter station is avoided.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A new energy island power grid system sending out through a flexible direct current overhead line is characterized by comprising a new energy electric field, a sending end flexible direct current converter station, a receiving end flexible direct current converter station, a bipolar direct current overhead line, an energy storage device and an alternating current energy consumption device;
the transmission end flexible direct current converter station comprises a transmission end boosting converter transformer and a transmission end flexible direct current converter, the new energy electric field is commonly connected to the transmission end boosting converter transformer through a three-phase alternating current bus, and the transmission end boosting converter transformer is connected with the transmission end flexible direct current converter;
the number of the sending end flexible direct current converter stations is multiple, and the multiple sending end flexible direct current converter stations are connected in parallel;
the receiving-end flexible direct current converter station comprises a receiving-end converter transformer and a receiving-end flexible direct current converter, and the receiving-end flexible direct current converter is connected with the receiving-end converter transformer;
the sending end flexible direct current converter is connected with the receiving end flexible direct current converter through a bipolar direct current overhead line;
the alternating current energy consumption device and the energy storage device are connected between the new energy electric field and the sending end converter station;
all sending end flexible direct current converter stations adopt a double-closed-loop constant alternating current voltage and frequency control strategy, only one receiving end flexible direct current converter station adopts a constant direct current voltage control strategy, the other receiving end flexible direct current converter stations adopt a constant active power control strategy, and bipolar control in the double-closed-loop constant alternating current voltage and frequency control strategy of the sending end flexible direct current converter stations adopts the same outer loop controller.
2. The new energy island power grid system of claim 1, further comprising a dc energy consuming device;
and the direct current energy consumption device is connected to a direct current outlet of the receiving-end flexible direct current converter.
3. The new energy island grid system of claim 2, wherein the dc energy consuming device is formed by series connection of IGBT devices.
4. The system for sending out a new energy island power grid from a flexible direct current overhead line according to claim 1, wherein the number of configuration groups of alternating current energy consumption devices is calculated according to a preset formula, and the preset formula is as follows:
wherein delta is 1 or 2,N Number of AC energy consuming devices Number of sets, P, for AC energy consuming devices Sending end bipolar power Active power, P, for a transmitting-end flexible DC converter Capacity of each group of ac energy consuming devices The capacity of each group of alternating current energy consumption devices.
5. The system for sending out the new energy island power grid through the flexible direct current overhead line according to claim 4, wherein each group of alternating current energy consumption devices is composed of star-connected resistance series IGBT devices.
6. The new energy island grid system for sending out through the flexible direct current overhead line according to claim 1, wherein the sending end boost converter transformer and the receiving end converter transformer are delta/Y0 double-winding transformers or Y/Y0 double-winding transformers or three-winding transformers.
7. The new energy island power grid sending-out system through the flexible direct current overhead line according to claim 1, wherein the bipolar direct current overhead line and the sending-end flexible direct current converter are connected through a smoothing reactor, and the bipolar direct current overhead line and the receiving-end flexible direct current converter are connected through a smoothing reactor.
8. The new energy island power grid system of claim 1, wherein the number of the receiving end flexible direct current converter stations is one or more than two.
9. The system for sending out the new energy island power grid through the flexible direct current overhead line according to claim 1, wherein the sending end flexible direct current converter and the receiving end flexible direct current converter are both in a single valve bank form or a double valve bank series connection form, each valve bank is in a three-phase six-leg structure, each leg is formed by connecting a plurality of power modules and a leg reactor in series, and each power module is a full-bridge submodule or a module mixed with a half-bridge submodule.
10. The new energy island power grid system sending out through the flexible direct current overhead line according to claim 1, characterized in that the sending end flexible direct current converter and the receiving end flexible direct current converter of each pole are formed by connecting more than two flexible direct current converters in series.
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| CN117060406B (en) * | 2023-10-12 | 2023-12-08 | 四川大学 | Operation method of flexible direct current transmission system based on OWT-DMMC |
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