CN115036955A - Flexible loop closing topology device applied to low-voltage power distribution network and control method thereof - Google Patents

Flexible loop closing topology device applied to low-voltage power distribution network and control method thereof Download PDF

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Publication number
CN115036955A
CN115036955A CN202210556573.7A CN202210556573A CN115036955A CN 115036955 A CN115036955 A CN 115036955A CN 202210556573 A CN202210556573 A CN 202210556573A CN 115036955 A CN115036955 A CN 115036955A
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China
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module
voltage
shared module
grid
power
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CN202210556573.7A
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Inventor
陈武
赵海熙
何晓坤
蒋玮
赵剑锋
曲小慧
曹武
雷家兴
梅军
王江峰
沈湛
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Southeast University
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Southeast University
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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
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
    • H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
    • H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
    • H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention discloses a flexible loop closing topological device applied to a low-voltage distribution network and a control method thereof, relating to the technical field of power generation, power transformation or power distribution and comprising a shared module and a non-shared module, in the case of a 380V low-voltage distribution network, 24 switching tubes with 800V withstand voltage are needed by BTB-VSC, while the proposed topology requires 18 switching tubes with a withstand voltage of 600V and 6 with a withstand voltage of 450V, thereby effectively reducing the equipment cost, ensuring the switch tubes connected in series at the same side to be switched on and off simultaneously without adopting a special control technology, and uses the carrier phase shift PWM modulation technology to ensure that the equivalent switching frequency is higher, the harmonic content of the system is less, the filter inductance is smaller, the number of the switching tubes through which current flows is small, so that the power transmission efficiency is improved to a certain extent, and the shared module and the non-shared module have multiple schemes and have a large development space.

Description

Flexible loop closing topology device applied to low-voltage power distribution network and control method thereof
Technical Field
The invention relates to the technical field of power generation, power transformation or power distribution, in particular to a flexible loop-closing topological device applied to a low-voltage power distribution network and a control method thereof.
Background
With the shift of global energy structures, power systems are facing huge changes, and more distributed power generation units and energy storage devices are equipped into the power systems. The more complex the structure of the power distribution network system becomes, the more line-crossing of voltage, the complex power flow, the high peak demand, the large feeder voltage drop and other problems cause the reduction of power supply reliability and power quality. In order to solve the problem, mechanical switches can be installed between different nodes of the power distribution network to adjust power flowing between the nodes, however, the traditional mechanical switches can generate larger impulse current at the moment of switching operation, and cannot flexibly adjust power flowing between different nodes according to the actual working state of the power distribution network, so that the requirement of power distribution network intellectualization is more and more difficult to meet.
The flexible loop closing device is used as a flexible power electronic device for replacing a traditional mechanical switch, not only can realize and replace the basic function of the traditional mechanical switch, but also can not generate larger impact current at the loop closing moment, and has the auxiliary functions of continuous power flow regulation, load balancing, error isolation, fault recovery and the like, so that the flexible loop closing device gradually becomes a research hotspot in the field of power distribution networks in recent years.
In the aspect of low-Voltage distribution network flexible loop closing device topology, what has been adopted at present is Back-To-Back Voltage Source Converter (BTB-VSC), and traditional BTB-VSC topology adopts two converters VSC1 and VSC2 To connect Back-To-Back via public direct current capacitance, and the same one side of every looks bridge arm adopts two switch tubes To establish ties in order To undertake higher Voltage stress, and this kind of topological control is simple, and the theory is ripe, nevertheless has following several not enoughly: a special control technology is needed to ensure that the switching tubes connected in series at the same side are simultaneously switched on and off; the voltage stress born by the switching tube is still large, and the switching tube with a large voltage withstanding value needs to be used; the number of the switching tubes through which the current flows is large, so that the power transmission efficiency is reduced; therefore, a flexible loop-closing topological device applied to a low-voltage distribution network and a control method thereof are provided.
Disclosure of Invention
In order to solve the above mentioned drawbacks in the background art, the present invention provides a flexible loop closing topology device applied to a low voltage distribution network and a control method thereof.
The purpose of the invention can be realized by the following technical scheme: the flexible loop-closing topological device comprises a shared module and a non-shared module, wherein the shared module is composed of three bridge arms and a direct current capacitor, the non-shared module is composed of two bridge arms at the network side, a multiplexing bridge arm and a direct current capacitor, and the shared module and the non-shared module share 24 switching tubes, 4 direct current capacitors and 2 groups of three-phase filters.
Furthermore, the middle points of two network side bridge arms of the non-shared module are connected with two power distribution network nodes through filters, alternating current incoming lines and alternating current outgoing lines of the three-phase topology are connected into an alternating current power grid in a star connection mode, and the middle point of each phase multiplexing bridge arm of the non-shared module is connected with the middle point of a corresponding bridge arm of the shared module.
Further, a first grid-side port of the non-shared module and the shared module ac port support a first grid ac voltage together, and a second grid-side port of the non-shared module and the shared module ac port support a second grid ac voltage together.
Furthermore, the shared module is responsible for controlling the stability of the direct-current voltage, providing the alternating-current voltage at an alternating-current port of the shared module, supporting the voltage of the power grid together with the unshared module, and the direct-current voltage of the shared module is not equal to the direct-current voltage of the unshared module.
Further, the non-shared module transmits active power to the distribution network node on the other side, and the direct current side of the shared module is not loaded, so that only reactive power flows.
Further, a control method of the flexible loop-closing topology device applied to the low-voltage distribution network comprises the following steps:
a voltage-current double closed-loop control strategy is adopted for a first grid side bridge arm of the non-shared module, the whole control is based on a dq rotating coordinate system, a voltage outer ring controls direct-current voltage stability of the non-shared module, a current inner ring controls first grid side current to be sinusoidal, and a generated modulation wave is subtracted from a modulation wave of the shared module to serve as a modulation wave of the first grid side bridge arm;
a power current double closed-loop control strategy is adopted by a second power grid side bridge arm of the non-shared module, the whole control is based on a dq rotation coordinate system, a power outer ring controls the whole device to transmit active power and reactive power to be constant, and a current inner ring ensures the second power grid side current to be sinusoidal. Subtracting the generated modulation wave from the common module modulation wave to be used as a modulation wave of a bridge arm at the second network side;
the multiplexing bridge arm of the unshared module adopts open-loop control, the amplitude of the modulation wave of the multiplexing bridge arm is the average of the amplitudes of the modulation waves of the two network side bridge arms, and the phase is the negative direction of the angular bisector of the two power grid voltage vectors;
the shared module is controlled by a single voltage ring;
and a PS-PWM modulation strategy is adopted between the non-shared module and the shared module.
The invention has the beneficial effects that:
in the using process of the invention, under the occasion of a 380V low-voltage distribution network, 24 switching tubes with withstand voltage value of 800V are needed by BTB-VSC, 18 switching tubes with withstand voltage value of 600V and 6 switching tubes with withstand voltage value of 450V are needed by the topology, so that the equipment cost is effectively reduced, a special control technology is not needed to ensure that the switching tubes connected in series at the same side are simultaneously switched on and off, and a carrier phase-shifting PWM (pulse width modulation) technology is used, so that the equivalent switching frequency is higher, the system harmonic content is less, the filter inductance is smaller, and the number of the switching tubes through which current flows is smaller, therefore, the power transmission efficiency is improved to a certain extent, a shared module and a non-shared module have multiple schemes, and a larger development space exists.
Drawings
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art to obtain other drawings without creative efforts;
FIG. 1 is a three-phase topology structure diagram of the common module flexible loop closing device of the present invention;
FIG. 2 is a simplified three-phase topology of the common module flexible loop closing apparatus of the present invention;
FIG. 3 is a single-phase topology structure diagram of the common module flexible loop closing device of the present invention;
FIG. 4 is a simplified single-phase topology of a common module flexible loop closing device;
FIG. 5 is a block diagram of a control strategy for a first grid-side arm of a non-shared module of the apparatus of the present invention;
FIG. 6 is a block diagram of a control strategy for a second grid-side arm of an unshared module of the present invention;
FIG. 7 is a block diagram of a non-shared module multiplexing bridge arm control strategy of the apparatus of the present invention;
FIG. 8 is a block diagram of a common module control strategy for the apparatus of the present invention;
FIG. 9 is a graph of the first grid side voltage current waveform of the apparatus of the present invention;
FIG. 10 is a graph of the second grid side voltage current waveform of the apparatus of the present invention;
FIG. 11 is a diagram of a DC voltage waveform of the present invention;
fig. 12 is a waveform diagram of the invention for transmitting active power and reactive power.
Detailed Description
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.
As shown in fig. 1, a flexible loop-closing topology device applied to a low-voltage distribution network includes a shared module and an unshared module, where the shared module is composed of three bridge arms and a dc capacitor, and the unshared module is composed of two network-side bridge arms, a multiplexing bridge arm and a dc capacitor, and it should be further explained that in a specific implementation process, the shared module and the unshared module collectively need 24 switching tubes, 4 dc capacitors and 2 groups of three-phase filters.
The middle points of two network side bridge arms of the non-shared module are connected with two power distribution network nodes through filters, and alternating current incoming lines and alternating current outgoing lines of the three-phase topology are connected into an alternating current power grid in a star connection mode. The middle point of each multiplexing bridge arm of the non-shared module is connected with the middle point of the corresponding bridge arm of the shared module, and it needs to be further explained that the design is used for sharing the voltage stress born by each switching tube in the specific implementation process.
It should be further noted that, in an implementation, the first grid-side port of the non-shared module and the shared module ac port support a first grid ac voltage together, and the second grid-side port of the non-shared module and the shared module ac port support a second grid ac voltage together.
It should be further noted that, in the implementation process, the shared module is responsible for controlling the dc voltage stabilization and providing an ac voltage at an ac port thereof, and supports the grid voltage together with the unshared module, and the dc voltage of the shared module is not equal to the dc voltage of the unshared module.
It should be further noted that in the implementation process, the unshared module transmits active power to the node of the distribution network on the other side, and the direct current side of the shared module has no load, so that only reactive power flows, and the design has the advantage that the operation efficiency of the whole flexible loop closing device is improved.
It should be further noted that, in an implementation process, a method for controlling a flexible loop-closing topology device applied to a low-voltage distribution network includes:
a first grid side bridge arm of the non-shared module adopts a voltage-current double closed-loop control strategy, the whole control is based on a dq rotating coordinate system, a voltage outer ring controls the direct-current voltage of the non-shared module to be stable, a current inner ring controls the first grid side current to be sinusoidal, and the generated modulation wave is subtracted from the modulation wave of the shared module to be used as the modulation wave of the first grid side bridge arm;
a power current double closed loop control strategy is adopted by a second power grid side bridge arm of the non-shared module, the whole control is based on a dq rotation coordinate system, a power outer ring controls the whole device to transmit constant active power and reactive power, and a current inner ring ensures that the current on the second power grid side is sinusoidal. Subtracting the generated modulation wave from the common module modulation wave to be used as a modulation wave of a bridge arm at the second network side;
the multiplexing bridge arm of the unshared module adopts open-loop control, the amplitude of the modulation wave of the multiplexing bridge arm is the average of the amplitudes of the modulation waves of the two network side bridge arms, and the phase is the negative direction of the angular bisector of the two power grid voltage vectors;
the shared module is controlled by a single voltage ring and is responsible for controlling the current and voltage stability of the shared module;
it should be further explained that the PS-PWM modulation strategy is used between the non-shared module and the shared module, and in the specific implementation process, the advantage of this design is to increase the equivalent switching frequency.
The following table shows the parameters of the module-shared flexible loop closing device in this example
Parameter(s) Numerical value Parameter(s) Numerical value
First network voltage u g1 /V 380∠0° Non-shared module DC capacitor C dc /mF 20
Second network voltage u g2 /V 380∠30° Common module DC capacitor C dc /mF 20
DC voltage u of non-shared module dc /V 300 Filter inductance L/mH 0.5
DC voltage u of non-shared module dc /V 200
Transmission power P/kW 250
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed.

Claims (6)

1. The flexible loop-closing topology device is characterized in that the flexible loop-closing topology device is connected with a first power grid and a second power grid in a star shape respectively, the flexible loop-closing topology device comprises a shared module and an unshared module, the unshared module is connected with the shared module in series, the shared module is composed of three bridge arms and a direct current capacitor, the unshared module is composed of two bridge arms on the grid side, a multiplexing bridge arm and a direct current capacitor, and the shared module and the unshared module share 24 switching tubes, 4 direct current capacitors and 2 groups of three-phase filters.
2. The flexible loop-closing topology device applied to the low-voltage distribution network of claim 1 is characterized in that the midpoints of two network-side bridge arms of the unshared module are connected with two distribution network nodes through filters, an alternating current incoming line and an alternating current outgoing line of the three-phase topology are connected into an alternating current power grid in a star connection mode, and the midpoint of each phase multiplexing bridge arm of the unshared module is connected with the midpoint of a corresponding bridge arm of the shared module.
3. The flexible closed-loop topology device applied to a low-voltage distribution network according to claim 2, wherein a first grid-side port of the non-shared module and the shared module ac port support a first grid ac voltage together, and a second grid-side port of the non-shared module and the shared module ac port support a second grid ac voltage together.
4. The flexible loop-closing topology device applied to the low-voltage distribution network of claim 3, wherein the shared module is responsible for controlling the stabilization of the DC voltage and providing the AC voltage at the AC port thereof, and supports the grid voltage together with the unshared module, and the DC voltage of the shared module is not equal to the DC voltage of the unshared module.
5. The flexible loop-closing topology device applied to the low-voltage distribution network in claim 4, wherein the non-shared module transmits active power to the nodes of the distribution network on the other side, and the direct-current side of the shared module has no load, so only reactive power flows.
6. A control method of a flexible loop-closing topological device applied to a low-voltage distribution network is characterized by comprising the following steps:
a first grid side bridge arm of the non-shared module adopts a voltage-current double closed-loop control strategy, the whole control is based on a dq rotating coordinate system, a voltage outer ring controls the direct-current voltage of the non-shared module to be stable, a current inner ring controls the first grid side current to be sinusoidal, and the generated modulation wave is subtracted from the modulation wave of the shared module to be used as the modulation wave of the first grid side bridge arm;
a power current double closed-loop control strategy is adopted by a second power grid side bridge arm of the non-shared module, the whole control is based on a dq rotation coordinate system, a power outer ring controls the whole device to transmit active power and reactive power to be constant, and a current inner ring ensures the second power grid side current to be sinusoidal. Subtracting the generated modulation wave from the common module modulation wave to be used as a modulation wave of a bridge arm at the second network side;
the multiplexing bridge arm of the unshared module adopts open-loop control, the amplitude of the modulation wave of the multiplexing bridge arm is the average of the amplitudes of the modulation waves of the two network side bridge arms, and the phase is the negative direction of the angular bisector of the two power grid voltage vectors;
the shared module is controlled by a single voltage ring;
and a PS-PWM modulation strategy is adopted between the non-shared module and the shared module.
CN202210556573.7A 2022-05-17 2022-05-17 Flexible loop closing topology device applied to low-voltage power distribution network and control method thereof Pending CN115036955A (en)

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CN202210556573.7A CN115036955A (en) 2022-05-17 2022-05-17 Flexible loop closing topology device applied to low-voltage power distribution network and control method thereof

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CN202210556573.7A CN115036955A (en) 2022-05-17 2022-05-17 Flexible loop closing topology device applied to low-voltage power distribution network and control method thereof

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