CN115377986B - 360-degree full-range orthogonal power flow controller and working method - Google Patents

360-degree full-range orthogonal power flow controller and working method Download PDF

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CN115377986B
CN115377986B CN202211292087.5A CN202211292087A CN115377986B CN 115377986 B CN115377986 B CN 115377986B CN 202211292087 A CN202211292087 A CN 202211292087A CN 115377986 B CN115377986 B CN 115377986B
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power flow
flow controller
phase
output
input
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CN115377986A (en
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张友军
姚崇
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Suzhou University
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Suzhou 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
    • H02J3/04—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
    • 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
    • H02M5/02—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 without intermediate conversion into dc
    • H02M5/04—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 without intermediate conversion into dc by static converters
    • H02M5/22—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 without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M5/275—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 without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/293—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 without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M5/2932—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 without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage, current or power
    • H02M5/2937—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 without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage, current or power using whole cycle control, i.e. switching an integer number of whole or half cycles of the AC input voltage
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]

Abstract

The invention relates to a 360-degree full-range orthogonal power flow controller and a working method thereof, wherein the controller comprises a three-phase input transformation module; a direct power flow controller module; the three-phase output transformation module comprises a three-phase two-winding output transformer, and the output end of each phase of output transformer is connected to the original power grid in series; the direct power flow controller module comprises three full-bridge Buck alternating current circuits, each phase input transformation module is connected with the input ends of the three full-bridge Buck alternating current circuits, any full-bridge Buck alternating current circuit is provided with a plurality of switching tubes, and the controllability of compensating voltage amplitude and phase positions is realized by controlling duty ratio signals of the switching tubes in the full-bridge Buck alternating current circuits to change according to a sine rule. The total compensation voltage is connected in series into an original power grid to realize the control of active power flow and reactive power flow in the power grid; the phase adjustment range of the compensation voltage can reach 360 degrees, the control is flexible, and the control of active power flow and reactive power flow in a power grid is easy to realize.

Description

360-degree full-range orthogonal power flow controller and working method
Technical Field
The invention belongs to the technical field of power electronic transformation technology and power systems, and particularly relates to a 360-degree full-range orthogonal power flow controller and a working method.
Background
With the rapid development of urban economy, the continuous increase of the electric energy demand makes the load of a transmission line larger and larger, voltage fluctuation is generated, the efficiency and the stability of power transmission are seriously influenced by power transmission, and therefore, the optimization of power flow control in a power transmission system is one of the keys in the field of current power transmission.
Most current power flow control methods are controlled by changing and compensating parameters such as voltage amplitude, phase and line impedance, and most effectively use a Unified Power Flow Controller (UPFC). The concept of the unified power flow controller UPFC was first proposed by Gyugyi in 1992.
The UPFC realizes a voltage source connected in series in a circuit by utilizing a power electronic switch principle, plays the roles of circuit parameter compensation, independent reactive compensation and circuit power flow control, has excellent power flow control performance and can perform quick dynamic response on the change of power flow.
The UPFC engineering obtains good benefits after being put into use, but the defects of high price, great maintenance cost, large loss and the like limit the wide application of the UPFC engineering. Therefore, the power flow controller with excellent performance, high reliability and lower cost has fewer research results, so that the circuit structure is simple, the number of components in the circuit is reduced, devices (such as direct current capacitors) with high failure rate and short service life cycle are avoided, the engineering cost and the operation and maintenance cost are reduced, the economy of the power flow controller is improved, and the power flow consumption and control capacity under the non-ideal condition of a power grid is improved.
The publication No. CN109088410A discloses a phase 360 ° orthogonal direct power flow controller and a working method thereof, and the previous patent can only realize the adjustment of the phase 360 ° of the compensation voltage by selecting the combination of the switch modules in 6 switch modes. And in a switching mode the phase adjustment range of the compensation voltage is only + -30 deg.. The circuit structure is complex, and the control mode is complicated. Continuous and accurate control cannot be achieved when the phase of the compensation voltage is required to vary within 360 °.
Disclosure of Invention
The invention aims to provide a 360-degree full-range orthogonal power flow controller and a working method, wherein the controller is relatively simple in circuit structure and simple in control mode, and can flexibly realize continuous and accurate change of a compensation voltage phase within 360 degrees.
In order to achieve the purpose, the invention provides the following technical scheme: a 360 ° full range orthogonal power flow controller comprising:
the three-phase input transformation module comprises a three-phase two-winding input transformer with an input end and an output end, wherein the input end of each phase of the input transformer is connected to the original power grid in parallel;
the direct power flow controller module is provided with an input end and an output end, and the input end of the direct power flow controller module is respectively connected with the output end of the input transformation module of each phase to form compensation voltage;
the three-phase output transformation module comprises a three-phase two-winding output transformer with an input end and an output end, the input end of each phase of the output transformer is respectively connected with the output end of the direct power flow controller module, and the output end of each phase of the output transformer is connected with an original power grid in series;
the direct power flow controller module comprises three full-bridge Buck alternating current circuits, the output end of the input transformation module is connected with the input end of each full-bridge Buck alternating current circuit, the full-bridge Buck alternating current circuits are provided with a plurality of switch tubes, and the controllability of the amplitude value and the phase position of the compensation voltage can be realized by controlling the duty ratio signals of the switch tubes in the full-bridge Buck alternating current circuits to change according to the sine rule.
Optionally, in the above 360 ° full-range orthogonal power flow controller, the direct power flow controller module includes three orthogonal direct power flow controller submodules, each of the orthogonal direct power flow controller submodules has a first input end, a second input end, a first output end and a second output end, and the first input end and the second input end of each of the orthogonal direct power flow controller submodules are connected to the output end of the three-phase input transformation module respectively;
each orthogonal direct power flow controller submodule comprises the full-bridge Buck alternating current circuit.
Optionally, in the above 360 ° full-range orthogonal power flow controller, each full-bridge Buck ac circuit includes a first switch unit, a second switch unit, a third switch unit and a fourth switch unit, which are identical in structure, where the first switch unit includes a first switch tube and a second switch tube, the second switch unit includes a third switch tube and a fourth switch tube, the third switch unit includes a fifth switch tube and a sixth switch tube, and the fourth switch unit includes a seventh switch tube and an eighth switch tube;
the emitter of the first switch tube is connected with the emitter of the second switch tube, the collector of the first switch tube is connected with the collector of the fifth switch tube, the connection point serves as the first input end, the emitter of the fifth switch tube is connected with the emitter of the sixth switch tube, the collector of the sixth switch tube is connected with the collector of the seventh switch tube, the connection point serves as the second output end, the emitter of the seventh switch tube is connected with the emitter of the eighth switch tube, the collector of the eighth switch tube is connected with the collector of the fourth switch tube, the connection point serves as the second input end, the emitter of the fourth switch tube is connected with the emitter of the third switch tube, the collector of the third switch tube is connected with the collector of the second switch tube, and the connection point serves as the first output end.
Optionally, in the 360 ° full-range orthogonal power flow controller, an input end of the three-phase input transformation module is connected to the original power grid in a triangular manner;
and the output end of the three-phase input transformation module is respectively connected with the submodules of the three orthogonal direct power flow controllers.
Optionally, in the above 360 ° full-range orthogonal power flow controller, the input end of the three-phase input transformation module is connected to the original power grid in a star shape;
the 360-degree full-range orthogonal power flow controller further comprises an input filtering module arranged between the three-phase input transformation module and the direct power flow controller module, the input filtering module comprises three input filters, and each input filter is respectively connected with the output end of each phase of input transformation module and the input end of each orthogonal direct power flow controller submodule.
Optionally, in the above 360 ° full-range orthogonal power flow controller, the input end of the three-phase output transformation module is triangularly connected with the output end of the direct power flow controller module.
Optionally, in the 360 ° full-range orthogonal power flow controller, the 360 ° full-range orthogonal power flow controller further includes an output filter module disposed between the direct power flow controller module and the three-phase output transformer module;
the input end of the output filter module is connected with the output end of the direct power flow controller module, and the output end of the output filter module is connected with the input end of the three-phase output transformation module.
Optionally, in the 360 ° full-range orthogonal power flow controller, the second output ends of the three orthogonal direct power flow controller submodules are connected to each other, and the first output end of each orthogonal direct power flow controller submodule is connected to the input end of the output filter module.
Optionally, in the 360 ° full-range orthogonal power flow controller, the output filter module includes three inductors and three capacitors, the first output end of each orthogonal direct power flow controller submodule is connected to the three inductors, and one capacitor is connected between every two inductors and then connected to the input end of the three-phase output transformer module.
The invention also provides a working method of the 360-degree full-range orthogonal power flow controller, which comprises the 360-degree full-range orthogonal power flow controller, and comprises the following steps:
the secondary side output end of the three-phase input transformation module is respectively connected to the input end of the corresponding full-bridge Buck alternating current circuit through an input filter or directly;
the method comprises the steps that duty ratio signals of Buck alternating-current circuits in a direct power flow controller submodule are controlled to change according to a sine rule that the frequency is twice of the frequency of input voltage, and fundamental wave signals and third harmonic signals with controllable phases and amplitudes in a certain voltage range are obtained;
a first output end of each orthogonal direct power flow controller submodule is connected with a primary side input end of a three-phase output transformation module through an output filtering module, and a second output end of each orthogonal direct power flow controller submodule is connected;
the primary side input end of the three-phase output transformation module is connected with the output end of the output filter module in a triangular mode, so that third harmonic signals are cancelled out, compensation voltage with controllable phase and amplitude within a certain voltage range is obtained at the secondary side output end of the three-phase output transformation module, the total compensation voltage is connected into an original power grid in series, and therefore active power flow and reactive power flow in the power grid are controlled.
The invention has the beneficial effects that: (1) The invention realizes the controllability of the amplitude and the phase of the compensation voltage by controlling the control signal of the switching tube in the full-bridge Buck alternating current circuit to change according to the sine rule. The output end of the three-phase output transformation module obtains fundamental wave signals and third harmonic signals with controllable phases and amplitudes within a certain voltage range, the third harmonic signals are cancelled out in windings in triangular connection at the input end of the three-phase output transformation module, compensation voltages with controllable phases and amplitudes within a certain voltage range are obtained at the output end, and the total compensation voltage is connected into an original power grid in series, so that the control of active power flow and reactive power flow in the power grid is realized; the compensation voltage phase adjusting range can reach 360 degrees, the control is flexible, and the control of active power flow and reactive power flow in a power grid is easy to realize.
(2) Compared with the prior art, the invention can realize the accurate adjustment of the output compensation voltage within the range of 360 degrees of phase without the help of a selection switch, has continuous adjustment process, improves the circuit performance, and has simpler circuit structure and better economy because of no need of the selection switch.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to make the technical solutions of the present invention practical in accordance with the contents of the specification, the following detailed description is given of preferred embodiments of the present invention with reference to the accompanying drawings.
Drawings
Fig. 1 is a topology diagram of a 360 ° full range orthogonal power flow controller according to the present invention;
fig. 2 is a schematic structural diagram of a full-bridge Buck ac circuit in the 360 ° full-range orthogonal power flow controller in fig. 1;
FIG. 3 (a) is a schematic diagram of the adjustment range of the compensation voltage according to the embodiment of the present invention;
FIG. 3 (b) is a schematic diagram of the adjustment range of the compensation voltage in a certain state according to an embodiment of the present invention;
FIG. 4 shows k in an embodiment of the present invention 0 ，k 2 A value area schematic diagram;
FIG. 5 is a schematic diagram of the compensation voltage synthesis according to the embodiment of the present invention;
FIG. 6 is a diagram illustrating the synthesis of the compensation voltage phase taking the extreme value according to the embodiment of the present invention;
FIG. 7 (a) shows the compensation voltage amplitude extremum and k in one embodiment of the present invention 0 A relationship diagram of (1);
FIG. 7 (b) is a diagram illustrating the compensation voltage phase extremum and k according to one embodiment of the present invention 0 A relationship diagram of (1);
FIG. 8 (a) is a schematic diagram of a compensation voltage synthesis provided in an embodiment of the present invention;
FIG. 8 (b) is a graph of the compensation voltage range that can be used with the above control method;
fig. 9 (a) is a three-phase input transformation module in an embodiment of the present invention;
fig. 9 (b) shows a three-phase output transformer module according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of a switch tube control signal according to an embodiment of the present invention;
fig. 11 is a topology diagram of a 360 full range orthogonal power flow controller in another embodiment of the invention.
Detailed Description
The technical solutions of the present application will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are only some embodiments of the present application, but not all embodiments. The present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
In this application, where the context does not dictate to the contrary, the use of directional terms such as "upper, lower, top, bottom" generally refers to the orientation as shown in the drawings, or to the component itself in a vertical, perpendicular, or gravitational orientation; similarly, "inner and outer" refer to inner and outer relative to the profile of the components themselves for ease of understanding and description, but the above directional terms are not intended to limit the present application.
Referring to fig. 1 and fig. 9 (b), the 360 ° full-range orthogonal power flow controller according to a preferred embodiment of the present invention realizes the control of active power flow and reactive power flow in the power grid by connecting the total compensation voltage in series to the original power grid.
The 360-degree full-range orthogonal power flow controller comprises a three-phase input transformation module Ts, a direct power flow controller module, a three-phase output transformation module To and a filtering output module arranged between the direct power flow controller module and the three-phase output transformation module To.
The three-phase input transformation module Ts comprises a three-phase two-winding input transformer with an input end and an output end respectively; the direct power flow controller module comprises three orthogonal direct power flow controller submodules, and each orthogonal direct power flow controller submodule comprises a first input end, a second input end, a first output end and a second output end. The three-phase output transformation module To comprises a three-phase two-winding output transformer with an input end and an output end respectively.
The input end of a three-phase input transformation module Ts is connected To a high-voltage power grid in parallel, the output end of the three-phase input transformation module Ts is connected with the first input end and the second input end of three orthogonal direct power flow controller sub-modules respectively, the second output ends of the three orthogonal direct power flow controller sub-modules are connected with each other, the first output ends of the three orthogonal direct power flow controller sub-modules are connected with the input end of an output filter module respectively, the output end of the output filter module is connected with the input end of a three-phase output transformation module To respectively, and the output end of the three-phase output transformation module To is connected To the original power grid in series. It should be noted that, in this embodiment, the input end of the three-phase output transformation module To is connected To the output end of the output filter module in a triangular shape.
For convenience of description, in the present embodiment, three orthogonal direct power flow controller sub-modules are respectively defined as se:Sub>A first orthogonal direct power flow controller sub-module DPFC-se:Sub>A, se:Sub>A second orthogonal direct power flow controller sub-module DPFC-B, and se:Sub>A third orthogonal direct power flow controller sub-module DPFC-C. And the first orthogonal direct power flow controller submodule DPFC-A, the second orthogonal direct power flow controller submodule DPFC-B and the third orthogonal direct power flow controller submodule DPFC-C respectively comprise se:Sub>A full-bridge Buck alternating current circuit, and each full-bridge Buck alternating current circuit is provided with an input end and an output end.
Any full-bridge Buck alternating current circuit is provided with a plurality of switching tubes, and the controllability of the amplitude value and the phase position of compensation voltage is realized by controlling duty ratio signals of the switching tubes in the full-bridge Buck alternating current circuit to change according to a sine rule, so that total compensation voltage is connected into an original power grid in series, and the control of active power flow and reactive power flow in the power grid is realized.
In this embodiment, referring to fig. 1 and fig. 9 (a), the input windings of the three-phase two-winding input transformer are connected in a star shape. At the moment, the 360-degree full-range orthogonal power flow controller further comprises an input filtering module arranged between the three-phase input transformation module Ts and the direct power flow controller module, and the output end of the three-phase input transformation module Ts is connected with the input end of the input filtering module and then respectively connected with the input ends of a plurality of full-bridge Buck alternating current circuits of the three orthogonal direct power flow controller sub-modules.
Correspondingly, the input filter module comprises three input filters, the input ends of the three input filters are respectively connected with the output ends of the three-phase two-winding input transformer, the output ends of the three input filters are respectively connected with the input ends of the three full-bridge Buck alternating current circuits, so that a sine control signal with the frequency being twice of the frequency of the input voltage is added into a switch tube control signal of the full-bridge Buck alternating current circuit in the direct power flow controller To obtain a fundamental wave signal and a third harmonic signal, and after the fundamental wave signal and the third harmonic signal pass through the three-phase output transformation module To, the third harmonic signal is mutually counteracted in a winding in triangular connection at the input end of the three-phase output transformation module To, and compensation voltage continuously adjusted in a certain range is obtained. In other embodiments, the input end of the three-phase input transformation module Ts may also be connected to the original power grid in a delta shape, and at this time, the output end of the three-phase input transformation module Ts is directly connected to the input ends of the full-bridge Buck ac circuits of the three orthogonal direct power flow controller sub-modules, respectively.
Specifically, the first orthogonal direct power flow controller submodule DPFC-A comprises an A-phase Buck alternating current circuit Buck-se:Sub>A; the second orthogonal direct power flow controller sub-module DPFC-B comprises a B-phase Buck alternating current circuit Buck-B; and the third orthogonal direct power flow controller sub-module DPFC-C comprises a C-phase Buck alternating current circuit Buck-C.
Referring to fig. 1, 9 (a) and 9 (b), the input end of the three-phase two-winding input transformer includes an a-phase input winding a 1 (ii) a B-phase input winding B 1 (ii) a C-phase input winding C 1 . The output end of the three-phase two-winding input transformer comprises an A-phase output winding a 1s (ii) a B-phase output winding B 1s (ii) a C-phase output winding C 1s . Wherein, the A-phase input winding a 1 B phase input winding B 1 And C phase input winding C 1 Has the same number of turns, and an A-phase output winding a 1s Phase B output winding B 1s And C phase output winding C 1s Are the same.
A-phase output winding a of three-phase two-winding input transformer 1s The Buck alternating current circuit Buck-se:Sub>A is connected to the input end of se:Sub>A first orthogonal direct power flow controller submodule DPFC-A, and the B-phase output winding B 1s The Buck alternating current circuit Buck-B is connected to the input end of a Buck alternating current circuit Buck-B of a second orthogonal direct current controller submodule DPFC-B, and the C-phase output winding C 1s And the Buck alternating current circuit Buck-C is connected to the input end of the third orthogonal direct current controller sub-module DPFC-C.
Each full-bridge Buck alternating-current circuit comprises a plurality of mutually connected switching tubes, so that the controllability of the amplitude and the phase of the compensation voltage is realized by controlling the duty ratio of the switching tubes in the full-bridge Buck alternating-current circuit to change according to a sine rule.
Specifically, referring to fig. 1 and 2, each full-bridge Buck ac circuit includes four switch units with the same structure. In this embodiment, four switch units having the same structure are defined as the first switch unit S 1 A second switch unit S 2 And a third switch unit S 3 And a fourth switching unit S 4 . Wherein, four switch units that the structure is the same all include two interconnect's switch tube.
For the sake of easy distinction, the first switching unit comprises a first switching tube S 1a And a second switching tube S 1b (ii) a The second switch unit comprises a third switch tube S 2a And a fourth switching tube S 2b (ii) a The third switching unit comprises a fifth switching tube S 3a And a sixth switching tube S 3b (ii) a The fourth switching unit comprises a seventh switching tube S 4a And an eighth switching tube S 4b 。
With a first switch unit S 1 For example, the connection method is as follows: first switch tube S 1a Emitter and second switch tube S 1b Is connected to the first switching tube S 1a Collector and fifth switch tube S 3a Is used as se:Sub>A first input end of se:Sub>A first orthogonal type direct power flow controller submodule DPFC-A and is connected to an A-phase output winding se:Sub>A of se:Sub>A three-phase input transformation module Ts 1s First output terminal A of 1， Fifth switch tube S 3a Emitter and sixth switching tube S 3b Is connected to the sixth switching tube S 3b Collector and seventh switching tube S 4a As se:Sub>A second output terminal of the first orthogonal direct power flow controller submodule DPFC-se:Sub>A, se:Sub>A seventh switching tube S 4a Emitter and eighth switching tube S 4b Is connected to the eighth switching tube S 4b Collector and fourth switch tube S 2b Is used as se:Sub>A second input end of se:Sub>A first orthogonal type direct power flow controller submodule DPFC-A and is connected to an A-phase output winding se:Sub>A of se:Sub>A three-phase input transformation module Ts 1s Second output terminal A 2， Fourth switch tube S 2b Emitter and third switch tube S 2a Is connected to the third switching tube S 2a Collector and second switch tube S 1b Is connected as se:Sub>A first output terminal of se:Sub>A first quadrature type direct power flow controller sub-module DPFC-se:Sub>A. Connecting se:Sub>A first output end of se:Sub>A first orthogonal direct power flow controller submodule DPFC-A To an input end A of se:Sub>A three-phase output transformation module To through an output filter 3 To (3).
It should be noted that all the switch tubes used above are IGBT switch tubes, however, the present invention is not limited to the use of IGBT switch tubes, and may be replaced by MOSFET switch tubes, etc. taking MOSFET switch tubes as an example, in this case, the source electrode of the MOSFET switch tube corresponds to the emitter electrode of the IGBT switch tube, and the drain electrode of the MOSFET switch tube corresponds to the collector electrode of the IGBT switch tube.
The output filter module further comprises three inductors and three capacitors, a first output end of each orthogonal direct power flow controller submodule is connected with the three inductors, and a capacitor is connected between every two inductors and then connected with an input end of the three-phase output transformation module To.
Specifically, as described above, the input terminal of the three-phase two-winding output transformer includes the a-phase input winding a 2 (ii) a B-phase input winding B 2 (ii) a C-phase input winding C 2 . The output end of the three-phase two-winding output transformer comprises an A-phase output winding a 2s (ii) a B-phase output winding B 2s (ii) a C-phase output winding C 2s 。
A-phase input end a of three-phase two-winding output transformer 2 se:Sub>A connection point E is formed by connecting an output transformer and an inductor with se:Sub>A first output end of se:Sub>A first orthogonal direct power flow controller submodule DPFC-A 1 Phase B input terminal B 2 The output transformer, an inductor and the first output end of the orthogonal direct power flow controller submodule DPFC-B are connected to form a connection point E 2 Phase C input terminal C 2 A connection point E is formed by connecting an output transformer, an inductor and the first output end of the third orthogonal direct power flow controller submodule DPFC-C 3 。
In another embodiment, referring to fig. 11, when each orthogonal direct power flow controller submodule includes a plurality of full-bridge Buck ac circuits (module 1, module 2, 8230; module n in fig. 11), the input transformation module Ts is a three-phase multi-winding transformer, and its primary side input terminal is the same as that of the previous embodiment, specifically referring to fig. 1, fig. 9 (a) and fig. 9 (b), which includes an a-phase input winding a 1 (ii) a B-phase input winding B 1 (ii) a C-phase input winding C 1 . The secondary side output end comprises an A-phase output winding N a1 Output winding N a2 823060, 8230305, output winding N an Phase B output winding N b1 Output winding N b2 823060, output winding N bn (ii) a C-phase output winding N c1 Output winding N c2 823060, 8230305, output winding N cn . Wherein, the A-phase input winding a 1 Phase BInput winding b 1 And C phase input winding C 1 Has the same number of turns, and an A-phase output winding N a1 Output winding N a2 823060, output winding N an Phase B output winding N b1 Output winding N b2 823060, 8230305, output winding N bn (ii) a C-phase output winding N c1 Output winding N c2 823060, output winding N cn The number of windings is the same.
In each orthogonal direct power flow controller submodule, each full-bridge Buck alternating current circuit module also has an input end and an output end, each input end is connected with a secondary side winding of a corresponding input transformation module, a plurality of output ends are connected in series to obtain the output voltage of each orthogonal direct power flow controller submodule, and a first output end E of a first full-bridge Buck alternating current circuit module is connected with a first output end E of a second full-bridge Buck alternating current circuit module 1 As the first output end of the sub-module of the orthogonal direct power flow controller, the second output end point F of the last full-bridge Buck alternating current circuit module is used 3 And the second output end is used as the second output end of the sub-module of the orthogonal direct power flow controller. The embodiment adopts a modular structure, and can obtain multi-level alternating current output voltage which can be adjusted in a high-voltage full range only by adopting a low-voltage-resistant switching device and a secondary side winding of a transformer; the circuit is easy to expand, good in portability, convenient to maintain, flexible and redundant in control and high in reliability of the whole circuit.
In summary, in the present invention, a group of three-phase line voltage windings of a three-phase input transformation module Ts are connected To three full-bridge Buck ac circuits of a three-phase voltage direct power flow controller, a control signal with a sinusoidal rule with a frequency twice the input voltage frequency is added To a switching tube To generate a fundamental wave signal and a third harmonic signal, a first output terminal of an orthogonal direct power flow controller submodule is connected To an input terminal of a three-phase output transformation module To through an output filter module, a second output terminal of the orthogonal direct power flow controller submodule is connected To each other, the third harmonic signal is cancelled in a triangle-connected input terminal winding of the three-phase output transformation module To, and a voltage with a controllable phase amplitude in a certain range is obtained at an output terminal of the three-phase output transformation module To.
The output ends of the three-phase output transformation modules To are connected into the corresponding power grid in series To obtain compensation voltage which is continuously adjusted within a certain range, so that active power flow and reactive power flow are respectively and independently and continuously controlled. The orthogonal direct power flow controller has the advantages of wide compensation voltage control range, controllable phase amplitude and flexible control, has the characteristics of simple circuit structure and flexible control, does not need a high-capacity direct current energy storage element, and has the advantages of simple circuit structure, good economy and high reliability.
The invention also provides a working method of the direct power flow controller, which comprises the following steps:
the output end of a Ts winding of the three-phase input transformation module is connected To the input end of each orthogonal type direct power flow controller submodule through the input filter module or directly respectively, the first output end of each orthogonal type direct power flow controller submodule is connected with the input end of the three-phase output transformation module To through the output filter module respectively, and the output end of the three-phase output transformation module To is connected To the original power grid in series.
For convenience of analysis, taking phase a as an example, the overall duty ratio of the orthogonal direct power flow controller submodule in fig. 2 is set as d. Switch unit S 1 、S 2 、S 3 、S 4 Respectively d 1 、d 2 、d 3 、d 4 . The input voltage of the sub-module of the orthogonal direct power flow controller is set as
Figure 744462DEST_PATH_IMAGE001
The output voltage of the orthogonal direct power flow controller submodule is U oa 。
Make the integral duty ratio of the sub-module of the orthogonal direct power flow controller
Figure 957269DEST_PATH_IMAGE002
，k 2 >0. When 0 is present<d<1 hour, switch unit S 1 Constant on, switch unit S 2 Constant off, switch unit S 3 ，S 4 Are alternately conducted, at the moment U oa =dU ia =d 4 U ia (ii) a When in use-1<d<At time 0, switch unit S 2 Constant on, switch unit S 1 Constant off, switching unit S 3 ，S 4 The control signals of the switching tubes are shown in FIG. 10 when the switching tubes are conducted alternately, at this time, U oa =dU ia =-d 3 U ia . Then output voltage of sub-module of orthogonal direct power flow controller
Figure 53270DEST_PATH_IMAGE003
(wherein U is oa1 Is a fundamental component, U oa2 As the third harmonic component). Order to
Figure 326119DEST_PATH_IMAGE004
，
Figure 244921DEST_PATH_IMAGE005
，
Figure 261419DEST_PATH_IMAGE006
To obtain k 0 ，k 2 The value range of (a) is shown in fig. 4. After the output voltages of the orthogonal direct power flow controller sub-modules pass through the three-phase output voltage transformation module To, three harmonic signals in the output voltages of the three orthogonal direct power flow controller sub-modules are mutually offset due To the fact that primary side windings are connected in a delta shape (triangular shape). The output voltage of the sub-module of the orthogonal direct power flow controller is only left
Figure 680767DEST_PATH_IMAGE007
(subsequent omission of U for ease of analysis i ) Let us order
Figure 514731DEST_PATH_IMAGE008
The compensation voltage adjustment range is shown in fig. 3 (a), with the origin O as the center,
Figure 652320DEST_PATH_IMAGE009
drawing a circle for radius, drawing a tangent EF of a circle O at a passing point E (1, 0) in a first quadrant, wherein the tangent point is F, the angle FOE =60 degrees, and the other quadrants are the same, so that a surrounded graph is the total compensation voltage adjusting range of the power flow controller,
obviously, when k is 0 =0, the adjustment range is centered around the origin O,
Figure 205266DEST_PATH_IMAGE010
is a circle of radius, when k 0 Where =1, the compensation voltage adjustment range is point E (1, 0). The tangent of the E circle O is crossed, the tangent point is F, and the angle EOF =60 °. When 0 is present<k 0 <1, assume that OA = k at this time 0 The adjustment range of the compensation voltage is a circle with an origin A and a radius AC as shown in FIG. 3 (b), and
Figure 885647DEST_PATH_IMAGE011
and point E is (1, 0), so AE =1-k 0 In the right triangle ACE, angle ACE =90 °,
Figure 31457DEST_PATH_IMAGE012
. Then < CEA =30 °, and also < FEO =30 °, so points F, C, E are on the same straight line. The other quadrants are the same, and the compensation voltage regulation range can be obtained.
The compensation voltage synthesis diagram is shown in FIG. 5, in which the vector OC represents the compensation voltage
Figure 390763DEST_PATH_IMAGE013
Vector OA represents the voltage component
Figure 749063DEST_PATH_IMAGE014
Vector AC represents a voltage component
Figure 408584DEST_PATH_IMAGE015
. The following can be obtained:
Figure 459716DEST_PATH_IMAGE016
；
Figure 181685DEST_PATH_IMAGE017
；
Figure 595873DEST_PATH_IMAGE018
；
Figure 329474DEST_PATH_IMAGE019
；
Figure 800775DEST_PATH_IMAGE020
；
the same relationship holds when point B is on OA.
1. Adjustable voltage amplitude extreme value and K 0 The relationship of (c):
taking the first quadrant as an example, the extreme value of the adjustable voltage amplitude is A as a dot,
Figure 885406DEST_PATH_IMAGE021
the distance from the origin to the two intersection points of the circle of radius and the x-axis.
At this time k 2 =1-k 0 ；
Figure 100355DEST_PATH_IMAGE022
；
Figure 219621DEST_PATH_IMAGE023
；
Obtaining the extreme value and K of the full-quadrant voltage amplitude 0 The relationship image of (2) is shown in FIG. 7 (a):
2. adjustable voltage phase extremum and k 0 The relationship of (c):
take the first quadrant as an example, when k 2 =1-k 0 ，OA=k 0 ，
Figure 596245DEST_PATH_IMAGE024
Symbol ACO =90 °, the compensation voltage is synthesized as shown in fig. 6:
Figure 433751DEST_PATH_IMAGE025
when the utility model is used, the water is discharged,
Figure 189742DEST_PATH_IMAGE026
;
Figure 429093DEST_PATH_IMAGE027
while the voltage phase can be adjusted
Figure 711039DEST_PATH_IMAGE028
。
Full quadrant voltage phase maximum
Figure 35841DEST_PATH_IMAGE029
And k is 0 FIG. 7 (b) shows the relationship (c).
The invention also provides a parameter selection method, and the compensation voltage synthesized by the method has the minimum proportion of the third harmonic content.
In the figure the vector OC represents the compensation voltage U o In a phase of
Figure 592593DEST_PATH_IMAGE030
Vector OA represents a voltage component
Figure 279926DEST_PATH_IMAGE031
Vector AC represents a voltage component
Figure 14664DEST_PATH_IMAGE032
. Due to the fact that
Figure 544871DEST_PATH_IMAGE033
. It is known that when k is 2 The smaller the magnitude of the third harmonic. Therefore, the optimal control method is as shown in fig. 8 (a):
the straight line passing through C and forming the line segment OA with the foot A, k 2 At a minimum, the third harmonic has the smallest amplitude.
Figure 656047DEST_PATH_IMAGE034
，
Figure 856609DEST_PATH_IMAGE035
。
The compensation voltage adjustment range of this control method is shown in fig. 8 (b):
when the compensation voltage is out of the above-mentioned regulation range, let k 2 =1-k 0 ，
When in use
Figure 27827DEST_PATH_IMAGE036
When it is used, make
Figure 451855DEST_PATH_IMAGE037
，
Figure 350410DEST_PATH_IMAGE038
;
When in use
Figure 340231DEST_PATH_IMAGE039
When it is used, order
Figure 213509DEST_PATH_IMAGE040
，
Figure 116045DEST_PATH_IMAGE041
;
Combined stand
Figure 755973DEST_PATH_IMAGE042
，
Finding k 0 Taking the maximum value after the value interval of (a), and then determining k 2 To finally determine the value of
Figure 928198DEST_PATH_IMAGE043
The value of (a) is,
Figure 706798DEST_PATH_IMAGE044
。
in summary, the invention adds a sinusoidal signal with the frequency twice as high as the frequency of the input voltage into the control signal of the switching tube of the full-bridge Buck alternating current unit, obtains the fundamental wave signal and the third harmonic wave signal after the phase and amplitude change at the output end, and outputs the first transformation module ToThe secondary side adopts a winding connected in a delta shape (triangle shape) To offset a third harmonic signal, fundamental wave components with changed phases and amplitudes, namely compensation voltage, are obtained on the secondary side of the three-phase output transformation module To, and then the output end of the secondary side of the three-phase output transformation module To is connected in series with the original power grid, so that the power flow control is carried out on the power grid. The compensation voltage has a phase adjustment range of
Figure 370997DEST_PATH_IMAGE045
。
The patent also provides a control method, under the control method, the amplitude of a third harmonic signal at the output end of a submodule of the orthogonal direct power flow controller can be effectively reduced, fundamental wave components are increased, and loss of a primary side winding of a three-phase output voltage transformation module To is reduced. The invention can realize continuous and accurate adjustment of the compensation voltage within the range of 360 degrees, has simple circuit structure, good economical efficiency and flexible control, and is easy to realize the control of active power flow and reactive power flow in the power grid.
In another embodiment, the circuit structure is as shown in fig. 11, when each orthogonal direct current controller submodule includes a plurality of full-bridge Buck ac circuits, each full-bridge Buck ac circuit is a submodule (module 1 or module 2 or module n). The control strategy of each orthogonal direct power flow controller submodule is similar to that of the previous embodiment, specifically, the control strategy of each full-bridge Buck alternating current circuit in the same orthogonal direct power flow controller submodule is the same, sinusoidal signals with the frequency being twice of the frequency of input voltage are added into control signals of a switch tube, a plurality of full-bridge Buck alternating current circuits are controlled to operate in a switching cycle through staggered high-frequency switching actions, the output ends of the full-bridge Buck alternating current circuits are connected in series, and the total output voltage, namely fundamental wave components and third harmonic components, of the orthogonal direct power flow controller submodule is obtained. The third harmonic components are mutually offset in the input end windings of the triangular connection of the three-phase output transformation module To, and the voltage with controllable phase amplitude in a certain range is obtained at the output end of the three-phase output transformation module To. Reference may be made in detail to the method of controlling a modular cascaded multilevel ac converter in publication CN 114825972A.
In the embodiment, only a low-voltage-withstanding switching device and a transformer secondary side winding are needed to be adopted to obtain the output voltage which can be adjusted in a high-voltage full range, and the modular structure enables the circuit to be easy to expand, good in portability, convenient to maintain, good in control flexibility and redundancy and higher in reliability of the whole circuit. Moreover, the modularized structure increases the equivalent switching frequency of the output voltage, reduces the voltage ripple, has less harmonic content and good output waveform quality, thereby reducing the output filter device, equivalently reducing the working frequency of the switching device and reducing the circuit loss.
All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to the above-described embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and shall cover the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (9)

1. A method of operating a 360 ° full range orthogonal power flow controller, the method comprising the steps of:
the output end of the secondary side of the three-phase input transformation module is respectively connected to the input end of the corresponding full-bridge Buck alternating current circuit through an input filter or directly;
the method comprises the steps that duty ratio signals of Buck alternating-current circuits in a direct power flow controller submodule are controlled to change according to a sine rule that the frequency is twice of the frequency of input voltage, and fundamental wave signals and third harmonic signals with controllable phases and amplitudes in a certain voltage range are obtained;
connecting a first output end of each orthogonal direct power flow controller submodule with a primary side input end of a three-phase output transformation module through an output filtering module, and connecting a second output end of each orthogonal direct power flow controller submodule;
the primary side input end of the three-phase output transformation module is connected with the output end of the output filter module in a triangular mode so as to cancel out the third harmonic signal, the compensation voltage with controllable phase and amplitude in a certain voltage range is obtained at the secondary side output end of the three-phase output transformation module, and the total compensation voltage is connected into the original power grid in series, so that the control of active power flow and reactive power flow in the power grid is realized;
the full-range orthogonal power flow controller comprises: the three-phase input transformation module comprises a three-phase two-winding input transformer with an input end and an output end, wherein the input end of each phase of the input transformer is connected to the original power grid in parallel;
the direct power flow controller module is provided with an input end and an output end, and the input end of the direct power flow controller module is respectively connected with the output end of the input transformation module of each phase to form compensation voltage;
the three-phase output transformation module comprises a three-phase two-winding output transformer with an input end and an output end, the input end of each phase of the output transformer is respectively connected with the output end of the direct power flow controller module, and the output end of each phase of the output transformer is connected with an original power grid in series;
wherein, direct trend controller module includes three full-bridge Buck AC circuit, every looks the output of input vary voltage module respectively with three the input of full-bridge Buck AC circuit is connected, arbitrary full-bridge Buck AC circuit is provided with a plurality of switch tubes, through control the duty cycle signal of the switch tube in the full-bridge Buck AC circuit changes according to sinusoidal law in order to realize the controllability of compensating voltage amplitude and phase place.
2. The method of operating a 360 ° full-range orthogonal power flow controller as claimed in claim 1, wherein the direct power flow controller module comprises three orthogonal direct power flow controller submodules, each of the orthogonal direct power flow controller submodules having a first input terminal, a second input terminal, a first output terminal and a second output terminal, the first input terminal and the second input terminal of each of the orthogonal direct power flow controller submodules being connected to the output terminals of the three-phase input transformation module;
each orthogonal direct power flow controller submodule comprises the full-bridge Buck alternating current circuit.
3. The method of operating a 360 ° full-range orthogonal power flow controller of claim 2, wherein each of the full-bridge Buck ac circuits comprises a first switching unit, a second switching unit, a third switching unit and a fourth switching unit which are identical in structure, the first switching unit comprises a first switching tube and a second switching tube, the second switching unit comprises a third switching tube and a fourth switching tube, the third switching unit comprises a fifth switching tube and a sixth switching tube, and the fourth switching unit comprises a seventh switching tube and an eighth switching tube;
the emitter of the first switch tube is connected with the emitter of the second switch tube, the collector of the first switch tube is connected with the collector of the fifth switch tube, the connection point serves as the first input end, the emitter of the fifth switch tube is connected with the emitter of the sixth switch tube, the collector of the sixth switch tube is connected with the collector of the seventh switch tube, the connection point serves as the second output end, the emitter of the seventh switch tube is connected with the emitter of the eighth switch tube, the collector of the eighth switch tube is connected with the collector of the fourth switch tube, the connection point serves as the second input end, the emitter of the fourth switch tube is connected with the emitter of the third switch tube, the collector of the third switch tube is connected with the collector of the second switch tube, and the connection point serves as the first output end.
4. A method of operation of a 360 ° full-range orthogonal power flow controller as claimed in claim 3, wherein the input of said three-phase input transformation module is delta connected to said original grid;
and the output end of the three-phase input transformation module is respectively connected with the submodules of the three orthogonal direct power flow controllers.
5. The operating method of a 360 ° full-range orthogonal power flow controller according to claim 3, wherein the input end of the three-phase input transformation module is star-connected to the original grid;
the 360-degree full-range orthogonal power flow controller further comprises an input filtering module arranged between the three-phase input transformation module and the direct power flow controller module, the input filtering module comprises three input filters, and each input filter is respectively connected with the output end of each phase of input transformation module and the input end of each orthogonal direct power flow controller submodule.
6. A method of operation of a 360 ° full range orthogonal power flow controller as claimed in claim 4 or 5, wherein the input of the three phase output transformation module is delta connected to the output of the direct power flow controller module.
7. The method of operation of a 360 ° full range quadrature type power flow controller as claimed in claim 6, wherein said 360 ° full range quadrature type power flow controller further comprises an output filtering module disposed between said direct power flow controller module and said three phase output transformation module;
the input end of the output filter module is connected with the output end of the direct power flow controller module, and the output end of the output filter module is connected with the input end of the three-phase output voltage transformation module.
8. The method of operating a 360 ° full-range orthogonal power flow controller of claim 6, wherein the second outputs of three said orthogonal direct power flow controller submodules are connected to each other, and the first output of each said orthogonal direct power flow controller submodule is connected to the input of the output filter module.
9. The operating method of a 360 ° full-range orthogonal power flow controller according to claim 8, wherein the output filter module comprises three inductors and three capacitors, the first output terminal of each orthogonal direct power flow controller submodule is connected with three inductors, and one capacitor is connected between every two inductors and then connected with the input terminal of the three-phase output transformer module.
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