CN115483683A - Flexible alternating-current loop closing device and system - Google Patents
Flexible alternating-current loop closing device and system Download PDFInfo
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- CN115483683A CN115483683A CN202211142904.9A CN202211142904A CN115483683A CN 115483683 A CN115483683 A CN 115483683A CN 202211142904 A CN202211142904 A CN 202211142904A CN 115483683 A CN115483683 A CN 115483683A
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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
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
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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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Abstract
The application provides a flexible interchange closes ring device and system. The flexible alternating current loop closing device comprises three-phase converter chains and a multi-winding transformer, wherein any one of the three-phase converter chains comprises N full-bridge submodules with cascaded alternating current ends and N voltage stabilizing units, N is an integer greater than or equal to 1, one end of any one of the three-phase converter chains is directly or through a first isolation transformer connected with a first alternating current system, and the other end of any one of the three-phase converter chains is directly or through a second isolation transformer connected with a second alternating current system; wherein: any one of the full-bridge sub-modules comprises a bridge circuit and a direct-current capacitor, the direct-current end of the bridge circuit is connected with the direct-current capacitor in parallel, the bridge circuit comprises four groups of power semiconductor devices, and the midpoint of the bridge circuit is the alternating-current end corresponding to the full-bridge sub-module; any one of the voltage stabilizing units comprises a single-phase full-bridge circuit or a three-phase half-bridge circuit, the direct current end of any one of the voltage stabilizing units is connected with the direct current capacitor of the corresponding full-bridge submodule in parallel, and the alternating current end is connected with the secondary winding of the multi-winding transformer.
Description
Technical Field
The application relates to the technical field of alternating current transmission, in particular to a flexible alternating current loop closing device and system.
Background
With the continuous improvement of the requirements of users on the quality of electric energy, the demand of electricity utilization, the reliability of power supply and the like, the closed loop operation mode of the power system is used for supplying power.
The closed-loop operation mode of the power system is a network closed operation mode formed by connecting lines, transformers or circuit breakers based on a power supply mode of a two-way power supply, and the power grid closed-loop operation has the advantages that the circuits, the transformers or the circuit breakers can be mutually transmitted and transformed, mutually supported and mutually adjusted and mutually reserved; therefore, the reliability of a power grid or power supply can be improved, and the power consumption of important loads can be ensured. But the operating conditions of loop closing are harsh, the voltage amplitude and the phase of two paths of power supplies are basically consistent, and the overload of each element in the loop network cannot be caused after the loop closing; however, in an actual system, due to the influence of system impedance distribution, the two power supplies actually have amplitude and phase angle differences, which cannot meet the condition of closed-loop operation, and the two power supplies and the load operate in isolation, which cannot realize the advantage of closed-loop operation.
In the prior art, a scheme for realizing flexible loop closing by using a power electronic converter is available, for example, AC-DC-AC converters are used for connecting AC buses of two power supplies, a DC bus is arranged between two back-to-back converters for isolation, and the AC side respectively adjusts the amplitude and phase of an AC voltage to realize flexible loop closing; and the load balance between the two power supplies can be realized by adjusting the load flow when the load of one power supply is heavier. However, the scheme has high cost, two sets of converters, namely rectification and inversion, are required, and when the power flow is regulated, the two sets of converters have full-power current to flow, so that the loss is high. Therefore, in the prior art, the parallel flexible loop closing scheme has low cost performance.
The above information disclosed in this background section is only for enhancement of understanding of the background of the application and therefore it may contain information that does not constitute prior art that is already known to a person of ordinary skill in the art.
Disclosure of Invention
In order to solve the above problems, the present application provides a flexible ac loop closing device and system.
According to a first aspect of the present application, a flexible ac loop closing device is provided, which is characterized in that the flexible ac loop closing device includes a three-phase converter chain and a multi-winding transformer, where any one of the three-phase converter chain includes N full-bridge submodules and N voltage stabilizing units, where N is an integer greater than or equal to 1, one end of any one of the three-phase converter chain is connected to a first ac system directly or through a first isolation transformer, and the other end of the any one of the three-phase converter chain is connected to a second ac system directly or through a second isolation transformer; wherein:
any one of the full-bridge sub-modules comprises a bridge circuit and a direct-current capacitor, the direct-current end of the bridge circuit is connected with the direct-current capacitor in parallel, the bridge circuit comprises four groups of power semiconductor devices, and the middle point of the bridge circuit is the alternating-current end corresponding to the full-bridge sub-module;
any one of the voltage stabilizing units comprises a single-phase full-bridge circuit or a three-phase half-bridge circuit, the direct current end of any one of the voltage stabilizing units is connected with the direct current capacitor of the corresponding full-bridge sub-module in parallel, and the alternating current end is connected with the secondary winding of the multi-winding transformer.
According to some embodiments, each of said converter chains further comprises a reactor connected in series with said N full-bridge submodules of the corresponding converter chain.
According to some embodiments, the first and/or second isolation transformer is a three-winding transformer or a two-winding transformer.
According to some embodiments, the primary winding of the multi-winding transformer is connected to a third ac system; or connecting the first communication system; or a secondary winding of the first isolation transformer is connected; or a third winding of the first isolation transformer is connected; or connecting the second communication system; or the secondary winding of the second isolation transformer is connected; or to a third winding of the second isolation transformer.
According to some embodiments, wherein:
the multi-winding transformer comprises a primary winding, and the primary winding of the multi-winding transformer is connected with the first alternating current system through a first alternating current switch, or is connected with a secondary winding of the first isolation transformer, or is connected with a third winding of the first isolation transformer; the primary winding is also connected with the second alternating current system through a second alternating current switch, or connected with a secondary winding of the second isolation transformer, or connected with a third winding of the second isolation transformer; or alternatively
The multi-winding transformer comprises a first primary winding and a second primary winding, and the first primary winding is connected with the first alternating current system through the first alternating current switch, or is connected with a secondary winding of the first isolation transformer, or is connected with a third winding of the first isolation transformer; the second primary winding passes through the second alternating current switch and is connected with the second alternating current system, or is connected with the secondary winding of the second isolation transformer, or is connected with the third winding of the second isolation transformer;
the first ac switch and the second ac switch are not closed at the same time.
According to some embodiments, the flexible ac loop closing device further comprises a first multi-winding transformer and a second multi-winding transformer, wherein:
the primary winding of the first multi-winding transformer is connected with the first alternating current system through a first alternating current switch, or is connected with the secondary winding of the first isolation transformer, or is connected with the third winding of the first isolation transformer;
and the primary winding of the second multi-winding transformer is connected with the second alternating current system through a second alternating current switch, or is connected with the secondary winding of the second isolation transformer, or is connected with the third winding of the second isolation transformer.
According to some embodiments, the ac terminals of M of the voltage stabilizing units are connected to the secondary winding of the first multi-winding transformer, and the ac terminals of N-M of the voltage stabilizing units are connected to the secondary winding of the second multi-winding transformer.
According to some embodiments, any one of the three-phase commutation chains is connected with a short-circuit switch in parallel.
According to some embodiments, the flexible AC loop closing device comprises i multi-winding transformers, i ≧ 2, the i multi-winding transformers comprising 3N secondary windings, any one of the i multi-winding transformers comprising 1 primary winding.
According to some embodiments, the multi-winding transformer further comprises a pre-charge unit comprising a pre-charge switch and a pre-charge resistor connected in parallel, the pre-charge unit being connected in series with the primary winding of the multi-winding transformer.
According to some embodiments, the number of full-bridge submodules that the flexible ac loop-closing device needs to access:
the Udc is the rated direct-current voltage of the full-bridge submodule; u1 is a phase voltage effective value at one end of the three-phase current conversion chain; u2 is the effective value of the phase voltage at the other end of the three-phase current conversion chain; and gamma is the phase angle difference of U1 and U2.
According to some embodiments, the ac terminal of any one of the N full-bridge submodules is connected in parallel with a bypass switch.
According to some embodiments, the ac terminal of any one of the N full-bridge submodules is connected in parallel with a bidirectional solid-state switch, wherein the bidirectional solid-state switch comprises a power semiconductor device, allowing a bidirectional current to flow, conducting in the event of an overvoltage on the dc capacitor of the submodule.
According to some embodiments, the system further comprises a dynamic reactive power compensation unit, wherein the dynamic reactive power compensation unit is connected with the first alternating current system, or a secondary winding of the first isolation transformer, or a third winding of the first isolation transformer; or the second alternating current system, or a secondary winding of the second isolation transformer, or a third winding of the second isolation transformer; the dynamic reactive power compensation unit is used for injecting reactive power to the connection point.
According to some embodiments, further comprising a diverter switch unit comprising a three phase isolating switch and two phase to phase switches, wherein:
the three-phase isolating switch is connected between the three-phase commutation chain and the first alternating current system in series or between the three-phase commutation chain and the second alternating current system in series;
the two interphase switches are connected between the three-phase isolating switch and the same side port of the three-phase current conversion chain, and the two interphase switches are bridged between different phase current conversion chains.
According to some embodiments, the flexible ac loop closing device comprises two sets of three-phase converter chains connected in parallel, each set of three-phase converter chains being connected in series with a diverter switch unit, the two sets of diverter switch units being arranged on different sides of the two sets of three-phase converter chains.
According to a second aspect of the present application, a flexible ac closing ring system is proposed, comprising: a first ac system, a second ac system, a flexible ac loop closure device as described in any of the first aspects.
According to some embodiments, further comprising: a first isolation transformer and a second isolation transformer.
The application provides a flexible alternating current loop closing device, connects between two sections of alternating current generating lines, and in the actual system, although there is voltage difference and phase angle difference between two sections of power supplies, the difference is less usually, and the commutation chain only needs to bear the voltage difference between two sections of alternating current power supplies, need not full capacity access when the device steady state operation, and the loss is very little.
The application provides a flexible AC closes ring device through adjusting device output voltage, changes the amplitude and the phase place of exerting at reactor both ends voltage actually, produces adjustable electric current on the reactor, realizes the nimble regulation and control of transmission active power and reactive power between two sections AC power supply.
The application provides a flexible AC loop closing device increases the energy supply return circuit based on multiconductor transformer and voltage stabilizing unit, and the multiconductor transformer passes through the primary side with alternating current power supply and inserts, provides multiple access mode to different connected modes between adaptation AC system and the device, the voltage stabilizing unit of secondary side connection submodule piece provides the alternating voltage source of stable isolation for voltage stabilizing unit. The voltage stabilizing unit comprises a single-phase full-bridge and three-phase half-bridge circuit with a two-level or/and three-level structure, a full-control power device is preferably adopted, four-quadrant operation can be realized, the sub-modules can obtain bidirectional active power support through the voltage stabilizing unit, reactive power on the alternating current side can also be adjusted, and an energy source is provided for flexibly adjusting and controlling the active power and the reactive power of the device current conversion chain.
The flexible alternating current loop closing device provided by the application utilizes the voltage difference between two sections of alternating current power supplies, the access capacity is obviously reduced, and the cost and the loss of the device have obvious advantages compared with a parallel scheme.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
The above and other objects, features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings. The drawings described below are for illustrative purposes only of certain embodiments of the present application and are not intended to limit the present application.
FIG. 1 illustrates an overall topology of an exemplary embodiment of a flexible ac loop closing device;
FIG. 2 illustrates a commutation chain topology of an exemplary embodiment;
FIG. 3 illustrates a schematic diagram of a voltage stabilization unit of an exemplary embodiment;
FIG. 4A shows a multi-winding transformer wiring schematic of an exemplary embodiment;
FIG. 4B illustrates yet another embodiment of an exemplary multi-winding transformer wiring schematic;
FIG. 4C illustrates yet another embodiment of an exemplary multi-winding transformer wiring schematic;
FIG. 4D illustrates yet another embodiment of an exemplary multi-winding transformer wiring schematic;
FIG. 5A illustrates yet another embodiment of an overall topology of an exemplary flexible ac loop closure device;
FIG. 5B illustrates yet another embodiment of an overall topology of an exemplary flexible ac loop closing device;
FIG. 6 illustrates yet another embodiment of an overall topology of an exemplary flexible ac loop closing device;
FIG. 7 illustrates a precharge unit schematic of an exemplary embodiment;
FIG. 8A illustrates an exemplary embodiment of a flexible AC loop closure device cum SVG topology;
fig. 8B illustrates yet another embodiment of an exemplary flexible ac loop closure device cum SVG topology.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and a repetitive description thereof will be omitted.
The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the embodiments of the disclosure can be practiced without one or more of the specific details, or with other means, components, materials, devices, etc. In such cases, well-known structures, methods, devices, implementations, materials, or operations are not shown or described in detail.
The flowcharts shown in the figures are illustrative only and do not necessarily include all of the contents and operations/steps, nor do they necessarily have to be performed in the order described. For example, some operations/steps may be decomposed, and some operations/steps may be combined or partially combined, so that the actual execution sequence may be changed according to the actual situation.
The terms "first," "second," and the like in the description and claims of the present application and in the above-described drawings are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.
It should be understood by those skilled in the art that the drawings are merely schematic representations of exemplary embodiments, and that the blocks or flowchart illustrations in the drawings are not necessarily required to practice the present application and, therefore, should not be considered to limit the scope of the present application.
Figure 1 illustrates an overall topology of a flexible ac loop closure device of an exemplary embodiment.
According to an exemplary embodiment, the flexible ac loop closing system comprises a flexible ac loop closing device, a first ac system S1 and a second ac system S2.
According to some embodiments, the flexible ac loop system further comprises a first isolation transformer T1 and a second isolation transformer T2.
As shown in fig. 1, the flexible ac loop closing device includes three-phase converter chains 11, 12, 13; one end S1A, S1B and S1C of the converter chain 1 is directly connected with the first alternating current system S1, or one end S1A, S1B and S1C of the converter chain 1 is connected with the first alternating current system S1 through a first isolation transformer T1; the other end S2A, S2B, S2C of the converter chain is directly connected to the second ac system S2, or the other end S2A, S2B, S2C of the converter chain passes through a second isolation transformer T2.
According to some embodiments, the flexible ac loop closing device provided by the present application is connected between two ac busbars, in an actual system, although there is a voltage difference and a phase angle difference between two power supplies, the difference is usually small, a converter chain only bears the voltage difference between the two ac power supplies, the flexible ac loop closing device does not need full capacity access when in steady-state operation, and the loss is very small
Fig. 2 illustrates a commutation chain topology of an exemplary embodiment.
As shown in FIG. 2, each phase conversion chain comprises N full-bridge submodules 2 and N voltage stabilizing units 3, wherein N is more than or equal to 1. Wherein: the alternating current ends of the full-bridge sub-modules 2 are cascaded, and each full-bridge sub-module 2 comprises a bridge circuit formed by four groups of power semiconductor devices and a direct current capacitor connected in parallel at the direct current end of the bridge circuit; the middle point of the bridge circuit is used as the alternating current end of the full bridge submodule 2.
According to an exemplary embodiment, the flexible ac loop closing device further comprises a multi-winding transformer TM.
According to some embodiments, the dc capacitor of the full-bridge submodule 2 is connected in parallel with the voltage stabilizing unit 3, and the voltage stabilizing unit 3 comprises a single-phase full-bridge circuit in a two-level structure or/and a three-phase half-bridge circuit in a three-level structure; the direct current end of the single-phase full-bridge circuit or the three-phase half-bridge circuit is connected in parallel with the two ends of the direct current capacitor of the full-bridge submodule 2, and the alternating current end of the single-phase full-bridge circuit or the three-phase half-bridge circuit is connected with the secondary side of the multi-winding transformer TM. The voltage regulation unit 3 in fig. 2 is an embodiment of a three-phase half-bridge circuit, and the voltage regulation unit 3 in fig. 3 is an embodiment of a single-phase full-bridge circuit.
According to some embodiments, the voltage regulation unit comprises a single-phase full-bridge, three-phase half-bridge circuit in a two-level or/and three-level configuration. Preferably, a full-control power device is adopted, four-quadrant operation can be realized, the sub-modules can obtain bidirectional active power support through the voltage stabilizing unit, reactive power on the alternating current side can also be adjusted, and an energy source is provided for flexible regulation and control of active power and reactive power of a current conversion chain of the flexible alternating current loop closing device.
According to some embodiments, each phase converter chain is also connected with a reactor 4 in series; the reactor 4 may be arranged at one end of the three-phase converter chain or in two parts at both ends of the converter chain. By adjusting the output voltage of the flexible alternating current loop closing device, the amplitude and the phase of the voltage actually applied to the two ends of the reactor 4 are changed, adjustable current is generated on the reactor 4, and flexible regulation and control of active power and reactive power transmitted between two sections of alternating current power supplies are realized.
According to some embodiments, the first isolation transformer T1 and/or the second isolation transformer T2 is a three-winding transformer or a two-winding transformer, the primary windings of the first and second isolation transformers are defined as windings connected to the ac system S1 or S2, the secondary windings are defined as windings connected to the converter chain 1, and when the first and second isolation transformers T1, T2 are three-winding transformers, the added windings are defined as a third winding.
According to some embodiments, the primary winding connection of the multi-winding transformer TM comprises: connecting a third ac system S3, as shown in fig. 4A; or to the first ac system S1, as shown in fig. 4B; or the secondary winding of the first isolation transformer T1 is connected, as shown in fig. 4C; or a third winding of the first isolation transformer T1, as shown in fig. 4D; or to a second ac system S2, as shown in fig. 4B; or the secondary winding of the second isolation transformer T2, as shown in fig. 4C; or to the third winding of the second isolation transformer T2 as shown in fig. 4D.
According to some working examples, the energy supply loop based on the multi-winding transformer TM and the voltage stabilizing unit 3 is added, the multi-winding transformer TM accesses an alternating current power supply through a primary winding, and the application provides multiple access modes to adapt to different connection modes between an alternating current system and the flexible alternating current loop closing device.
The secondary side of the multi-winding transformer TM is connected with the voltage stabilizing unit 3 of the submodule to provide a stable isolated alternating current voltage source for the voltage stabilizing unit 3.
According to some embodiments, the number of multi-winding transformers TM is 1, the number of primary windings is 1 or 2:
when the number of the primary windings is 1, the primary winding of the multi-winding transformer TM is connected with a first alternating current system S1, or a secondary winding of a first isolation transformer T1, or a third winding of the first isolation transformer T1 through a first alternating current switch K1; meanwhile, the primary winding is connected with a second alternating current system S2, or a secondary winding of a second isolation transformer T2, or a third winding of the second isolation transformer T2 through a second alternating current switch K2; as shown in fig. 5A.
When the number of the primary windings is 2, a first primary winding of the multi-winding transformer TM is connected with a first alternating current system S1, or a secondary winding of a first isolation transformer T1, or a third winding of the first isolation transformer T1 through a first alternating current switch K1; the second primary winding is connected with a second alternating current system S2, or a secondary winding of a second isolation transformer T2, or a third winding of the second isolation transformer T2 through a second alternating current switch K2; as shown in fig. 5B.
According to some embodiments, the first ac switch K1 and the second ac switch K2 are not closed at the same time.
According to some embodiments, the number of multi-winding transformers TM is 2, each multi-winding transformer comprising 1 primary winding, as shown in fig. 6:
a primary winding of a first multi-winding transformer TM1 is connected with a first alternating current system S1, or a secondary winding of a first isolation transformer T1, or a third winding of the first isolation transformer T1 through a first alternating current switch K1;
the primary winding of the second multi-winding transformer TM2 is connected to the second ac system S2, or the secondary winding of the second isolation transformer T2, or the third winding of the second isolation transformer T2 through the second ac switch K2.
The alternating current end of one part of voltage stabilizing unit in the three-phase converter chain is connected with the secondary winding of the first multi-winding transformer TM1, and the alternating current end of the other part of voltage stabilizing unit is connected with the secondary winding of the second multi-winding transformer TM 2;
according to some embodiments, each phase of the converter chain is also connected with a short-circuit switch K3 in parallel.
According to some embodiments, the number of multi-winding transformers TM is i (i ≧ 2), each multi-winding transformer contains 1 primary winding, and i multi-winding transformers TM contain 3 × n secondary windings in total.
According to some embodiments, the flexible ac loop apparatus further includes a pre-charging unit, including a pre-charging switch K4 and a pre-charging resistor R1 connected in parallel, the pre-charging unit being connected in the primary winding loop of the multi-winding transformer TM, as shown in fig. 7; by disconnecting the pre-charging switch K4 firstly, the power supply is connected through the pre-charging resistor R1, and the impact on the number TM of the multi-winding transformers when the power supply is directly connected can be prevented.
According to some embodiments, the number of sub-modules N satisfies the following condition:
wherein N is the number of submodules to be accessed by the flexible AC loop closing device, U dc Rated direct current voltage is provided for the full-bridge submodule; u shape 1 The effective value of the phase voltage at one end of the converter chain; u shape 2 The effective value of the phase voltage at the other end of the current conversion chain; and gamma is the phase angle difference of U1 and U2.
The application provides a flexible AC of tandem type closes ring device utilizes the voltage difference between two sections alternating current power supplies for the flexible AC of tandem type closes ring device access capacity and is showing and reduce, and the cost and the loss of device all have apparent advantage with the parallelly connected type scheme.
According to some embodiments, the alternating current end of the full-bridge sub-module is connected with the bypass switch in parallel; the bypass switch has the functions of controllable opening and closing and also has the function of power failure self-holding.
According to some embodiments, the ac terminals of the full bridge sub-modules are connected in parallel with the bidirectional solid state switch 12; the bi-directional solid state switch 12 comprises power semiconductors allowing bi-directional current flow, the bi-directional solid state switch 12 conducting in the event of an overvoltage in the sub-module dc capacitor.
According to an exemplary embodiment, the bidirectional solid-state switch 12 in this embodiment comprises anti-parallel thyristors, but the application is not limited thereto.
The implementation scheme of the application is illustrated by an embodiment:
the flexible alternating-current loop closing device is connected between a first alternating-current system S1 and a second alternating-current system S2 in an application mode, the effective values of the voltages of the power lines are 220kV, the transformation ratios of the isolation transformers T1 and T2 are 220kV/35kV, and the effective values of the voltages of two ends of each phase of a current conversion chain are
And (3) approximately equals to 20kV, assuming that an included angle between two ends of the power supply is 30 degrees, and the rated direct current voltage of the sub-modules is 2.2kV, thereby calculating the number of the sub-modules.
According to the condition calculation:
therefore, the minimum value of the number of the submodules required to be accessed by the flexible alternating-current loop closing device is 13, the total number of the secondary windings of the required multi-winding transformer TM is 13 multiplied by 3=39, and two multi-winding transformers TM1 and TM2 can be selected and respectively provided with 18 secondary windings and 21 secondary windings; or 1 multi-winding transformer TM with 39 secondary windings.
The application also provides an embodiment of double-ended reactive compensation decoupling.
The flexible alternating-current loop closing device further comprises a dynamic reactive compensation unit, and the dynamic reactive compensation unit is connected with the first alternating-current system S1, or a secondary winding of the first isolation transformer T1, or a third winding of the first isolation transformer T1; or the second ac system S2, or the secondary winding of the second isolation transformer T2, or the third winding of the second isolation transformer T2.
According to some embodiments, the dynamic reactive compensation unit may inject reactive power to the connection point.
According to some embodiments, the dynamic reactive compensation unit employs a chained Static Var Generator (SVG), or employs a Static Var Compensator (SVC), which is connected to the flexible ac loop device using a star or delta connection. Assuming that the flexible ac loop closing devices S1A, S1B, S1C and S2A, S2B, S2C have an angle of 0 ° between them, the phase voltages of the ports S1A, S1B, S1C and S2A, S2B, S2C are U1 and U2, respectively, and the ports S1A, S1B, S1C set a transfer capacitive reactive Q1= 3U 1 Ic (Ic is the effective value of the current flowing through the commutation chain), the ports S2A, S2B, S2C are forced to transfer Q2= 3U 2 Ic. Q2 can be compensated through the dynamic reactive compensation unit, and reactive independent decoupling of the ports S2A, S2B and S2C is achieved.
The application also provides an embodiment of the flexible alternating-current loop closing device and the SVG application.
Fig. 8A illustrates a flexible ac loop closure device cum SVG topology diagram of an exemplary embodiment.
As shown in fig. 8A, the flexible ac loop closing device further comprises one or two sets of switch units 5. Each group of the change-over switch units 5 comprises two interphase switches K4 and a three-phase isolating switch K5, and the three-phase isolating switch K5 is connected between the current conversion chain 1 and the first alternating current system S1 or the second alternating current system S2 in series; the interphase switch K4 is connected between the same side ports of the three-phase isolating switch K5, which are close to the commutation chain 1. Each group of the selector switch units 5 includes two interphase switches K4, and the two interphase switches K4 are connected to the AB phase and the BC phase, respectively.
According to some embodiments, the interphase switch K4 and the three-phase disconnecting switch K5 cannot be closed at the same time.
When K5 is closed and K4 is disconnected, the flexible alternating current loop closing device realizes the flexible alternating current loop closing function;
when K5 is disconnected and K4 is closed, the flexible alternating-current loop closing device achieves the SVG function, and further, active support can be provided for the SVG through the multi-winding transformer TM, and the function of a network construction converter is achieved.
Fig. 8B illustrates yet another embodiment of an exemplary flexible ac loop closing device cum SVG topology.
As shown in fig. 8B, the flexible ac loop closing device includes two sets of three-phase converter chains 1 connected in parallel, each set of three-phase converter chain 1 is connected in series with a set of switch unit 5, and the switch units 5 are disposed on different sides of the two sets of three-phase converter chains 1.
According to some embodiments, the flexible ac loop closing device can be used as SVG for two ac systems; or can be used as two flexible alternating current loop closing devices which are connected in parallel; and the loop closing device can also be used as a flexible alternating current loop closing device and an SVG for operation.
It should be clearly understood that this application describes how to make and use particular examples, but the application is not limited to any details of these examples. Rather, these principles can be applied to many other embodiments based on the teachings of the present disclosure.
Furthermore, it should be noted that the above-mentioned figures are only schematic illustrations of the processes involved in the method according to exemplary embodiments of the present application, and are not intended to be limiting. It will be readily understood that the processes shown in the above figures are not intended to indicate or limit the chronological order of the processes. In addition, it is also readily understood that these processes may be performed, for example, synchronously or asynchronously in multiple modules.
Exemplary embodiments of the present application are specifically illustrated and described above. It is to be understood that the application is not limited to the details of construction, arrangement, or method of implementation described herein; on the contrary, the application is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (18)
1. The flexible alternating current loop closing device is characterized by comprising three-phase converter chains and a multi-winding transformer, wherein any one of the three-phase converter chains comprises N full-bridge submodules with cascaded alternating current ends and N voltage stabilizing units, N is an integer greater than or equal to 1, one end of any one of the three-phase converter chains is directly or through a first isolation transformer connected with a first alternating current system, and the other end of the any one of the three-phase converter chains is directly or through a second isolation transformer connected with a second alternating current system; wherein:
any one of the full-bridge sub-modules comprises a bridge circuit and a direct-current capacitor, the direct-current end of the bridge circuit is connected with the direct-current capacitor in parallel, the bridge circuit comprises four groups of power semiconductor devices, and the midpoint of the bridge circuit is the alternating-current end corresponding to the full-bridge sub-module;
any one of the voltage stabilizing units comprises a single-phase full-bridge circuit or a three-phase half-bridge circuit, the direct current end of any one of the voltage stabilizing units is connected with the direct current capacitor of the corresponding full-bridge sub-module in parallel, and the alternating current end of the voltage stabilizing unit is connected with the secondary winding of the multi-winding transformer.
2. The flexible ac loop-closing device according to claim 1, wherein each of said converter chains further comprises a reactor connected in series with said N full-bridge submodules of the corresponding converter chain.
3. The flexible ac loop closing device according to claim 1, wherein said first isolation transformer and/or said second isolation transformer is a three-winding transformer or a two-winding transformer.
4. The flexible ac loop closing device according to claim 3, wherein the primary winding of said multi-winding transformer is connected to a third ac system; or connecting the first communication system; or a secondary winding of the first isolation transformer is connected; or a third winding of the first isolation transformer is connected; or connecting the second communication system; or the secondary winding of the second isolation transformer is connected; or a third winding of the second isolation transformer.
5. The flexible ac loop closing device according to claim 4, wherein:
the multi-winding transformer comprises a primary winding, and the primary winding of the multi-winding transformer is connected with the first alternating current system through a first alternating current switch, or is connected with a secondary winding of the first isolation transformer, or is connected with a third winding of the first isolation transformer; the primary winding is also connected with the second alternating current system through a second alternating current switch, or connected with a secondary winding of the second isolation transformer, or connected with a third winding of the second isolation transformer; or alternatively
The multi-winding transformer comprises a first primary winding and a second primary winding, and the first primary winding is connected with the first alternating current system through the first alternating current switch, or is connected with a secondary winding of the first isolation transformer, or is connected with a third winding of the first isolation transformer; the second primary winding passes through the second alternating current switch and is connected with the second alternating current system, or is connected with the secondary winding of the second isolation transformer, or is connected with the third winding of the second isolation transformer;
the first ac switch and the second ac switch are not closed at the same time.
6. The flexible ac loop-closing device of claim 4, further comprising a first multi-winding transformer and a second multi-winding transformer, wherein:
the primary winding of the first multi-winding transformer is connected with the first alternating current system through a first alternating current switch, or is connected with the secondary winding of the first isolation transformer, or is connected with the third winding of the first isolation transformer;
and the primary winding of the second multi-winding transformer is connected with the second alternating current system through a second alternating current switch, or is connected with the secondary winding of the second isolation transformer, or is connected with the third winding of the second isolation transformer.
7. The flexible ac loop-closing device according to claim 6, wherein the ac terminals of M said voltage stabilizing units are connected to the secondary winding of said first multi-winding transformer, and the ac terminals of N-M said voltage stabilizing units are connected to the secondary winding of said second multi-winding transformer.
8. The flexible ac loop closing device according to claim 6 or 7, wherein any one of said three phase commutation chains is connected in parallel with a short circuit switch.
9. The flexible ac loop-closing device according to claim 1, wherein said flexible ac loop-closing device comprises i multi-winding transformers, i ≧ 2, said i multi-winding transformers comprising 3N secondary windings, any of said i multi-winding transformers comprising 1 primary winding.
10. The flexible ac loop-closing device according to claim 1, further comprising a pre-charge unit comprising a pre-charge switch and a pre-charge resistor connected in parallel, the pre-charge unit being connected in series with the primary winding of the multi-winding transformer.
11. The flexible ac loop-closing device according to any of claims 1 to 10, characterized in that the number of full bridge submodules that the flexible ac loop-closing device needs to access:
wherein, U dc Rated direct current voltage of the full-bridge submodule; u shape 1 The effective value of the phase voltage at one end of the three-phase current conversion chain is obtained; u shape 2 The effective value of the phase voltage at the other end of the three-phase current conversion chain is obtained; gamma is U 1 And U 2 The phase angle difference of (c).
12. The flexible ac loop-closing device as claimed in claim 1, wherein the ac terminal of any one of the N full-bridge submodules is connected in parallel with a bypass switch.
13. The flexible ac loop-closing device according to claim 1, wherein the ac terminal of any one of said N full-bridge submodules is connected in parallel to a bidirectional solid-state switch, wherein said bidirectional solid-state switch comprises power semiconductors allowing bidirectional current to flow, conducting in case of overvoltage of the dc capacitor of the submodule.
14. The flexible ac loop closing device according to claim 3, further comprising a dynamic reactive compensation unit, wherein said dynamic reactive compensation unit is connected to said first ac system, or a secondary winding of said first isolation transformer, or a third winding of said first isolation transformer; or the second alternating current system, or a secondary winding of the second isolation transformer, or a third winding of the second isolation transformer; the dynamic reactive power compensation unit is used for injecting reactive power to the connection point.
15. The flexible ac loop closing device according to claim 1, further comprising a diverter switch unit comprising a three phase isolator and two phase to phase switches, wherein:
the three-phase isolating switch is connected in series between the three-phase commutation chain and the first alternating current system or between the three-phase commutation chain and the second alternating current system;
the two interphase switches are connected between the three-phase isolating switch and the same side port of the three-phase current conversion chain, and the two interphase switches are bridged between different phase current conversion chains.
16. The flexible ac loop closing device according to claim 1, wherein said flexible ac loop closing device comprises two sets of three-phase commutation chains connected in parallel, each set of three-phase commutation chains being connected in series with a set of diverter switch units, the two sets of diverter switch units being arranged on different sides of the two sets of three-phase commutation chains.
17. A flexible AC loop closure system, comprising: first ac system, second ac system, flexible ac loop closure device as claimed in any one of claims 1-16.
18. The flexible ac loop closing system as recited in claim 17, further comprising:
a first isolation transformer and a second isolation transformer.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
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| CN202211142904.9A CN115483683A (en) | 2022-09-20 | 2022-09-20 | Flexible alternating-current loop closing device and system |
| PCT/CN2023/119724 WO2024061215A1 (en) | 2022-09-20 | 2023-09-19 | Flexible alternating-current interconnection apparatus and startup control method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202211142904.9A CN115483683A (en) | 2022-09-20 | 2022-09-20 | Flexible alternating-current loop closing device and system |
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| CN115483683A true CN115483683A (en) | 2022-12-16 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2024061215A1 (en) * | 2022-09-20 | 2024-03-28 | 南京南瑞继保电气有限公司 | Flexible alternating-current interconnection apparatus and startup control method |
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