CN113258577B - Bipolar modulation 360-degree power flow controller and working method thereof - Google Patents
Bipolar modulation 360-degree power flow controller and working method thereof Download PDFInfo
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- CN113258577B CN113258577B CN202110648085.4A CN202110648085A CN113258577B CN 113258577 B CN113258577 B CN 113258577B CN 202110648085 A CN202110648085 A CN 202110648085A CN 113258577 B CN113258577 B CN 113258577B
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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
- 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
- H02M5/10—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 transformers
- H02M5/12—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 transformers for conversion of voltage or current amplitude only
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- 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
- H02M5/10—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 transformers
- H02M5/18—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 transformers for conversion of waveform
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Abstract
The invention discloses a bipolar modulation 360-degree power flow controller which comprises a three-phase input transformation module, a bipolar Buck alternating current unit circuit module and an output filtering module; the bipolar Buck alternating-current unit circuit module comprises a phase voltage bipolar Buck alternating-current unit circuit and a line voltage bipolar Buck alternating-current unit circuit, an output end of the phase voltage bipolar Buck alternating-current unit circuit is connected with an input end of the output filtering module after being connected with an output end of the line voltage bipolar Buck alternating-current unit circuit in series, phase voltage input into the voltage transformation module and line voltage with a phase difference of 90 degrees with the phase voltage input into the voltage transformation module are respectively connected with the phase voltage bipolar Buck alternating-current unit circuit and the line voltage bipolar Buck alternating-current unit circuit, and therefore 360-degree adjustment of amplitude and phase of output voltage is achieved. The invention can realize 360-degree adjustment of the amplitude and the phase of the output voltage, and realize independent or simultaneous adjustment of active power flow and reactive power flow, has more flexible control and simplifies the circuit structure.
Description
Technical Field
The invention relates to the technical field of power electronic conversion, in particular to a bipolar modulation 360-degree power flow controller and a working method thereof.
Background
With the development of society, the scale of a power grid is gradually enlarged, and the problem of uneven power flow distribution of power transmission and transformation equipment is gradually highlighted, so that the power supply capacity of the power grid is difficult to be fully utilized. The power flow in the power system comprises active power flow and reactive power flow, which are generally determined by a power supply, a load and a power supply network, and the difficulty of line reconstruction and power grid extension is gradually increased due to the limitation of urban planning. Therefore, how to improve the power transmission capacity of the power grid, improve the tide distribution and enhance the stability of the power system on the basis of the existing grid frame is a problem with important economic benefit and social significance.
For this reason, Flexible AC Transmission System (FACTS) technology is widely studied and applied. The FACTS device can control the phase angle, reactance and reactive voltage of alternating current, and improves the operation efficiency and stability of the intelligent power distribution network by providing or absorbing active power and reactive power. However, most FACTS devices have only one degree of freedom, and cannot control active power flow and reactive power flow in a power grid simultaneously and respectively, or due to the adoption of a large-capacity direct-current energy storage element, the FACTS that equipment failure rate is high, service life cycle is short, maintenance cost is high and the like are caused are many problems.
Although the two patents can respectively control active power flow and reactive power flow through primary power conversion, the two patents need to realize 360-degree adjustment of the output voltage phase of the power flow controller by additionally arranging an input selection switch and an output selection switch or increasing the number of single-phase Buck alternating current conversion circuits, and the topological structure and the control strategy are relatively complex.
The chinese patent publication No. CN108448906A discloses a vector-sum 360 ° phase and amplitude controllable ac converter and its operating method, which has the following disadvantages: (1) the topological structure is complex: for a power flow controller of a three-phase power grid, 9 single-phase Buck alternating-current units are needed, the total number of the Buck alternating-current units is 36, and the component cost and the loss are large. (2) The working principle is complex: the input ends of the three single-phase Buck alternating current units are respectively connected with A, B, C three-phase power supplies, and the angle between every two phases is 120 degrees. The duty ratio of one phase of Buck alternating current unit is zero, the output of the phase of Buck alternating current unit is zero, and the outputs of the other two phases of Buck alternating current units are connected in series to obtain an output voltage with a phase of 120 degrees and a controllable amplitude. If an output voltage with controllable 360-degree phase and amplitude is obtained, the working states of the three single-phase Buck alternating-current units must be switched, the duty ratio of one phase of Buck alternating-current unit is zero (namely, the Buck alternating-current units are in a non-working state), and the other two phases of Buck alternating-current units are in a working stateTo obtain. The output voltage of the single-phase Buck alternating-current unit can only be between 0 and 0U i The range is adjusted, and three 120-degree interval output voltage states have interval transition boundary lines during transition, so that the transition performance is poor; in actual operation, due to factors such as impedance, load or asymmetry of a three-phase power supply, when the output voltage of a converter in the prior art document CN108448906A, a vector-combined 360-degree phase and amplitude controllable ac converter and a working method thereof is transited in three 120-degree intervals, an angle gap is not adjusted, so that the output voltage is not adjusted continuously. (3) The control mode is complex and low in efficiency, and the three single-phase Buck alternating-current units are required to work simultaneously to realize the control mode, namely, the voltage regulation in the current same direction or the current vertical direction (namely, the active power flow regulation alone or the reactive power flow regulation alone). In addition, the forward and reverse regulation of active or reactive power flow also needs to be realized by switching the working state of the single-phase Buck alternating-current converter.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the defect that the output voltage phase of the power flow controller is adjusted by 360 degrees by additionally arranging an input selection switch or an output selection switch or increasing the number of single-phase Buck alternating-current conversion circuits in the prior art, so that the topological structure and the control strategy are relatively complex.
In order to solve the technical problem, the invention provides a bipolar modulation 360-degree power flow controller, wherein the input end of the power flow controller is connected with a high-voltage power grid in parallel, and the output end of the power flow controller is connected with the high-voltage power grid in series, and the bipolar modulation 360-degree power flow controller comprises a three-phase input voltage transformation module, a bipolar Buck alternating-current unit circuit module and an output filtering module;
the bipolar Buck alternating-current unit circuit module comprises a phase voltage bipolar Buck alternating-current unit circuit and a line voltage bipolar Buck alternating-current unit circuit, an output end of the phase voltage bipolar Buck alternating-current unit circuit is connected with an input end of the output filtering module after being connected with an output end of the line voltage bipolar Buck alternating-current unit circuit in series, output phase voltage of the three-phase input transformation module and output line voltage which is 90 degrees different from the phase voltage of the output phase voltage are respectively connected with the phase voltage bipolar Buck alternating-current unit circuit and the line voltage bipolar Buck alternating-current unit circuit, and 360-degree adjustment of amplitude and phase of the output voltage is achieved through the output filtering module.
In an embodiment of the invention, the bipolar Buck alternating-current unit circuit module comprises a first bipolar Buck alternating-current unit circuit sub-module, a second bipolar Buck alternating-current unit circuit sub-module and a third bipolar Buck alternating-current unit circuit sub-module, wherein the first bipolar Buck alternating-current unit circuit sub-module, the second bipolar Buck alternating-current unit circuit sub-module and the third bipolar Buck alternating-current unit circuit sub-module respectively comprise a phase voltage bipolar Buck alternating-current unit circuit and a line voltage bipolar Buck alternating-current unit circuit which are connected in series.
In one embodiment of the invention, the power supply further comprises a three-phase output transformation module, and the three-phase output transformation module is connected with the output filtering module.
In one embodiment of the invention, the output filtering module comprises a first output filter, a second output filter and a third output filter, wherein an input end of the first output filter is connected with an output end of the first bipolar Buck alternating current unit circuit submodule; the input end of the second output filter is connected with the output end of the second bipolar Buck alternating current unit circuit submodule; and the input end of the third output filter is connected with the output end of the third bipolar Buck alternating-current unit circuit submodule.
In one embodiment of the present invention, the first output filter, the second output filter and the third output filter each comprise an output filter inductor and an output filter capacitor.
In one embodiment of the present invention, the three-phase input transformation module comprises a first three-phase input transformer and a second three-phase input transformer, and the secondary sides of the first three-phase input transformer and the second three-phase input transformer are provided with center taps.
In one embodiment of the present invention, the primary side of the first three-phase input transformer is star-connected, and the secondary side thereof includes a phase voltage output winding; and the primary side of the second three-phase input transformer is in triangular connection, and the secondary side of the second three-phase input transformer comprises a line voltage output winding.
In one embodiment of the invention, the input of the primary side of the first three-phase input transformer and the input of the primary side of the second three-phase input transformer are connected in parallel to the high voltage grid.
In one embodiment of the invention, a phase voltage output winding of the first three-phase input transformer is connected with an input end of a phase voltage bipolar Buck alternating-current unit circuit; and the line voltage output winding of the second three-phase input transformer is connected with the input end of the line voltage bipolar Buck alternating current unit circuit.
In addition, the invention also provides a working method of the bipolar modulation 360-degree power flow controller, the output phase voltage of the three-phase input transformation module and the output line voltage with the phase difference of 90 degrees with the output phase voltage are respectively connected with the phase voltage bipolar Buck alternating current unit circuit and the line voltage bipolar Buck alternating current unit circuit, the amplitude value and the phase angle of the output voltage of the power flow controller are adjusted by respectively adjusting the duty ratio of the phase voltage bipolar Buck alternating current unit circuit and the line voltage bipolar Buck alternating current unit circuit, and the active power flow and the reactive power flow are adjusted independently or simultaneously.
Compared with the prior art, the technical scheme of the invention has the following advantages:
(1) in terms of topological structure, the invention is more concise:
the output phase voltage of the three-phase input transformation module and the output line voltage with the phase difference of 90 degrees with the output phase voltage are respectively connected with the phase voltage bipolar Buck alternating current unit circuit and the line voltage bipolar Buck alternating current unit circuit, and the output range of each bipolar Buck alternating current unit is-U i ToU i The output voltage amplitude and the phase are adjusted by 360 degrees under the condition of not adding an input selection switch or an output selection switch or increasing the number of Buck alternating unit circuits by respectively adjusting the duty ratios of the phase voltage bipolar Buck alternating unit circuit and the line voltage bipolar Buck alternating unit circuit, and for a power flow controller of a three-phase power grid, the invention only needs to add 6 bipolar Buck alternating single circuitsCompared with the prior art, the number of the switching tubes is 24, 1/3 is reduced, the switching tubes are simpler and more reliable, and loss is reduced;
(2) in the working principle, the invention is more concise:
the invention only needs two bipolar Buck alternating current units to be connected in series, wherein the input end of one bipolar Buck alternating current unit is connected with a phase voltage, the other bipolar Buck alternating current unit is connected with a line voltage which has a phase difference of 90 degrees with the phase voltage, and the output range of the bipolar Buck alternating current unit is within the range of-U i ToU i The range is adjustable, so that the output voltage of the two bipolar Buck alternating-current units which are connected in series is controllable in phase and amplitude of 360 degrees directly, the running state does not need to be switched continuously, no transition boundary line exists when the phase of the output voltage is adjusted in the range of 360 degrees, the conversion is more natural and is continuously controlled, and the output voltage is not influenced by factors such as impedance, load or three-phase unbalance of a power supply;
(3) in terms of a control method, the method is more direct and efficient:
under an ideal state, the power grid can be regarded as a pure resistive load state, the voltage and the current of the power grid are in the same direction, at the moment, the voltage of the power grid is adjusted in the current direction, the active power flow can be adjusted independently, and the voltage of the power grid is adjusted in the direction vertical to the current direction, so the reactive power flow can be adjusted independently; if the active power flow is independently regulated, only the bipolar Buck alternating current unit connected with the phase voltage needs to work, and the bipolar Buck alternating current unit connected with the line voltage does not need to work (the duty ratio is zero). If the reactive power flow is independently adjusted, the bipolar Buck alternating current unit connected with the line voltage is only required to work, and the bipolar Buck alternating current unit connected with the phase voltage is not required to work (the duty ratio is zero). When active power flow or reactive power flow is adjusted in the forward direction and the reverse direction, the duty ratio of the working bipolar Buck alternating-current unit is changed, and switching of different adjusting intervals is not needed. The control is more direct and efficient, and the dynamic performance is better.
Drawings
The invention is further described with reference to the following figures and examples.
Fig. 1 is a topology diagram of a bipolar modulation 360 ° power flow controller according to a first embodiment of the present invention.
Fig. 2 is a schematic diagram of the structure of DPFC-a of fig. 1.
Fig. 3 is a schematic diagram of the adjustment range of the output voltage of the single-phase voltage bipolar Buck ac unit circuit according to the embodiment of the present invention.
FIG. 4 is a schematic diagram of the regulation range of the output voltage of the bipolar Buck AC unit circuit for separately regulating the line voltage according to one embodiment of the present invention.
Fig. 5 is a schematic diagram of the adjustment range of the output voltage when the phase voltage bipolar Buck ac unit circuit and the line voltage bipolar Buck ac unit circuit are adjusted simultaneously according to the first embodiment of the present invention.
Detailed Description
Referring to fig. 1, the input end of a bipolar modulation 360-degree power flow controller is connected in parallel to a high-voltage power grid, and the output end of the power flow controller is connected in series to the high-voltage power grid. The power flow controller comprises a three-phase input transformation module, a bipolar Buck alternating-current unit circuit module, an output filtering module and a three-phase output transformation module.
The bipolar Buck alternating-current unit circuit module comprises a phase voltage bipolar Buck alternating-current unit circuit and a line voltage bipolar Buck alternating-current unit circuit, an output end of the phase voltage bipolar Buck alternating-current unit circuit is connected with an input end of an output filtering module after being connected with an output end of the line voltage bipolar Buck alternating-current unit circuit in series, an output phase voltage of a three-phase input transformation module and an output line voltage with a phase difference of 90 degrees with the output phase voltage are respectively connected with the phase voltage bipolar Buck alternating-current unit circuit and the line voltage bipolar Buck alternating-current unit circuit, and 360-degree adjustment of amplitude and phase of the output voltage is achieved through the output filtering module.
The bipolar Buck alternating-current unit circuit module comprises a first bipolar Buck alternating-current unit circuit sub-module DPFC-a, a second bipolar Buck alternating-current unit circuit sub-module DPFC-b and a third bipolar Buck alternating-current unit circuit sub-module DPFC-c, wherein the first bipolar Buck alternating-current unit circuit sub-module DPFC-a, the second bipolar Buck alternating-current unit circuit sub-module DPFC-b and the third bipolar Buck alternating-current unit circuit sub-module DPFC-c respectively comprise a phase voltage bipolar Buck alternating-current unit circuit and a line voltage bipolar Buck alternating-current unit circuit which are connected in series.
Specifically, the first bipolar Buck alternating current unit circuit submodule DPFC-a comprises an A-phase bipolar Buck alternating current unit circuit Buck-a and a BC-phase bipolar Buck alternating current unit circuit Buck-BC which are arranged in series; the second bipolar Buck alternating current unit circuit sub-module DPFC-B comprises a B-phase bipolar Buck alternating current unit circuit Buck-B and a CA-phase bipolar Buck alternating current unit circuit Buck-CA which are arranged in series; the third bipolar Buck alternating-current unit circuit submodule DPFC-C comprises a C-phase bipolar Buck alternating-current unit circuit Buck-C and an AB-phase bipolar Buck alternating-current unit circuit Buck-AB which are arranged in series. Buck-a, Buck-b and Buck-c are phase voltage bipolar Buck alternating current unit circuits, and Buck-bc, Buck-ca and Buck-ab are line voltage bipolar Buck alternating current unit circuits.
The output filtering module comprises a first output filter, a second output filter and a third output filter, wherein the input end of the first output filter is connected with the output end of the first bipolar Buck alternating current unit circuit submodule DPFC-a; the input end of the second output filter is connected with the output end of the second bipolar Buck alternating current unit circuit sub-module DPFC-b; the input end of the third output filter is connected with the output end of the third bipolar Buck alternating-current unit circuit submodule DPFC-c.
Specifically, the output end of the A-phase bipolar Buck alternating current unit circuit Buck-a and the output end of the BC-phase bipolar Buck alternating current unit circuit Buck-BC are connected in series and then connected to the input end of a first output filter, the output end of the B-phase bipolar Buck alternating current unit circuit Buck-B and the output end of the CA-phase bipolar Buck alternating current unit circuit Buck-CA are connected in series and then connected to the input end of a second output filter, and the output end of the C-phase bipolar Buck alternating current unit circuit Buck-C and the output end of the AB-phase bipolar Buck alternating current unit circuit Buck-AB are connected in series and then connected to the input end of a third output filter.
Also, the first output filter includes a first output filter inductorL faAnd a first output filter capacitorC fa(ii) a The second output filter comprises a second output filter inductorL fbAnd a second output filter capacitorC fb(ii) a The third output filter comprises a third output filter inductorL fcAnd a third output filter capacitorC fc。
The output filter is used for filtering high-frequency harmonic components generated by high-frequency on-off of the switching tube in the bipolar Buck alternating-current unit circuit submodule connected with the output filter.
In the above technical solution, the three-phase input transformation module includes a first three-phase input transformer Ti1And a second three-phase input transformer Ti2. First three-phase input transformer Ti1And a second three-phase input transformer Ti2The input terminal of the primary side of the transformer T is connected in parallel to a high-voltage network, and a first three-phase input transformer Ti1And a second three-phase input transformer Ti2The secondary side of the transformer is provided with a center tap.
The turn ratio of the first three-phase input transformer is Ni1The turn ratio of the second three-phase input transformer is Ni2It satisfies the relationship:
。
in particular, a first three-phase input transformer Ti1The primary side of the transformer is in star connection, and the secondary side of the transformer comprises an A-phase output winding Na1B phase output winding Nb1C phase output winding Nc1. Second three-phase input transformer Ti2The primary side of the transformer is in triangular connection, and the secondary side of the transformer comprises an AB phase output winding Nab1CA phase output winding Nca1BC phase output winding Nbc1。
First three-phase input transformer Ti1A phase output winding Na1Connected to the input end of the A-phase bipolar Buck AC unit circuit Buck-a, and the B-phase output winding Nb1Connected to the input end of the B-phase bipolar Buck AC unit circuit Buck-B, and the C-phase output winding Nc1Is connected to the input end of the C-phase bipolar Buck alternating current unit circuit Buck-C. Second three-phase input transformer Ti2BC phase output winding Nbc1Connected to the input end of a BC-phase bipolar Buck AC unit circuit Buck-BC, and a CA-phase output winding Nca1Connected to the input end of the CA-phase bipolar Buck AC unit circuit Buck-CA, and the AB-phase output winding Nab1And the input end of the AB-phase bipolar Buck AC unit circuit Buck-AB is connected.
The specific structure of the first, second and third bipolar Buck ac unit circuit sub-modules DPFC-a, DPFC-b and DPFC-c will be explained below.
Referring to FIG. 2, taking the DPFC-a sub-module as an example, the A-phase bipolar Buck AC unit circuit Buck-a includes a first switch tube Sa1-pA second switch tube Sa1-nA third switch tube Sa2-pAnd a fourth switching tube Sa2-n. Wherein, the first switch tube Sa1-pAnd a second switching tube Sa1-nForm a first four-quadrant switching tube Sa1(ii) a Third switch tube Sa2-pAnd a fourth switching tube Sa2-nForm a second four-quadrant switching tube Sa2. First switch tube Sa1-pAnd a second switching tube Sa1-nIs connected with the third switching tube Sa2-pEmitter and fourth switching tube Sa2-nIs connected with the emitter of the second switching tube Sa1-nCollector and third switching tube Sa2-pIs connected with the collector of the first switching tube Sa1-pIs connected to a first three-phase input transformer Ti1A phase output winding Na1A first output terminal of the fourth switching tube Sa2-nIs connected to a first three-phase input transformer Ti1A phase output winding Na1A second output terminal of the second switching tube Sa1-nCollector and third switching tube Sa2-pIs connected to a first output filter inductor of a first output filterL fa The front end of (a); the BC-phase bipolar Buck alternating-current unit circuit Buck-BC comprises a fifth switching tube Sa3-pThe sixth switching tube Sa3-nSeventh switching tube Sa4-pAnd an eighth switching tube Sa4-n . Wherein, the fifth switch tube Sa3-pThe sixth switching tube Sa3-nForm a third four-quadrant switching tube Sa3(ii) a Seventh switching tube Sa4-pAnd an eighth switching tube Sa4-nForm a fourth four-quadrant switching tube Sa4(ii) a Fifth switch tube Sa3-pEmitter and sixth switching tube Sa3-nIs connected with the emitting electrode of the seventh switching tube Sa4-pEmitter and eighth switching tube Sa4-nIs connected with the sixth switching tube Sa3-nCollector and seventh switching tube Sa4-pIs connected with the collector of the fifth switching tube Sa3-pIs connected to a second three-phase input transformer Ti2BC phase output winding Nbc1The eighth switching tube Sa4-nIs connected to a second three-phase input transformer Ti2BC phase output winding Nbc1A sixth switching tube Sa3-nCollector and seventh switching tube Sa4-pIs connected to a first three-phase input transformer Ti1A phase output winding Na1A center tap connection point of (a); second three-phase input transformer Ti2BC phase output winding Nbc1Is connected to the back end of the first output filter capacitor.
The switch tubes used above are all IGBT switch tubes, however, the present invention is not limited to the use of IGBT switch tubes, and may also be replaced by MOSFET switch tubes, etc., taking MOSFET switch tubes as an example, in which case, the source of MOSFET switch tubes corresponds to the emitter of IGBT switch tubes, and the drain of MOSFET switch tubes corresponds to the collector of IGBT switch tubes.
The specific structure of the second bipolar Buck ac unit circuit sub-module DPFC-b and the third bipolar Buck ac unit circuit sub-module DPFC-c is the same as the internal structure of the first bipolar Buck ac unit circuit sub-module DPFC-a, and the input and output connection mode thereof may refer to the first bipolar Buck ac unit circuit sub-module DPFC-a.
In summary, the output phase voltage of the three-phase input transformation module and the output line voltage which has a phase difference of 90 degrees with the output phase voltage are respectively connected with the phase voltage bipolar Buck alternating current unit circuit and the line voltage bipolar Buck alternating current unit circuit, and by respectively adjusting the duty ratios of the phase voltage bipolar Buck alternating current unit circuit and the line voltage bipolar Buck alternating current unit circuit, under the condition that an input selection switch or an output selection switch is not required to be additionally arranged or the number of the Buck alternating current unit circuits is not required to be increased, 360-degree adjustment of the amplitude and the phase of the output voltage is achieved, and the active power flow and the reactive power flow are adjusted independently or simultaneously, so that the control is more flexible, the circuit structure is simplified, and the safety and the reliability are improved.
In addition, the invention also provides a working method of the bipolar modulation 360-degree power flow controller, which is characterized in that the output phase voltage of the three-phase input transformation module and the output line voltage with the phase difference of 90 degrees with the output phase voltage are respectively connected with the phase voltage bipolar Buck alternating current unit circuit and the line voltage bipolar Buck alternating current unit circuit, the output voltage amplitude and the phase angle of the power flow controller are adjusted by respectively adjusting the duty ratio of the phase voltage bipolar Buck alternating current unit circuit and the line voltage bipolar Buck alternating current unit circuit, and the active power flow and the reactive power flow are adjusted independently or simultaneously.
The specific working principle is as follows:
when the power flow controller works, the three working states of the phase voltage bipolar Buck alternating current unit circuit connected with the phase voltage and the line voltage with the phase angle difference of 90 degrees can be divided into three working states, namely the phase voltage bipolar Buck alternating current unit circuit connected with the phase voltage which is independently regulated, the line voltage bipolar Buck alternating current unit circuit connected with the line voltage which is independently regulated, the phase voltage bipolar Buck alternating current unit circuit connected with the line voltage which is simultaneously regulated and the line voltage between the other two phases which is connected with the phase voltage, and the line voltage bipolar Buck alternating current unit circuit. The specific implementation is as follows:
1. phase voltage bipolar Buck alternating current unit circuit connected with phase voltage independently regulated
When the bipolar Buck alternating-current unit circuit works in a phase voltage bipolar Buck alternating-current unit circuit connected with an independent regulation phase voltage, taking a first bipolar Buck alternating-current unit circuit sub-module DPFC-a as an example: taking the A-phase bipolar Buck AC unit circuit Buck-a and the BC-phase bipolar Buck AC unit circuit Buck-BC as examples, the duty ratio of the BC-phase bipolar Buck AC unit circuit Buck-BC is setd a2Is 0.5, and the BC-phase bipolar Buck AC unitThe output voltage of the circuit Buck-bc is zero. Setting the duty ratio of an A-phase bipolar Buck AC unit circuit Buck-ad a1In [0,1 ]]In a range of regulation with an output voltage of value (2)d a1-1）u ia ,In [ -u ia,u ia]And (4) adjusting within a range. At this timeu oaIn thatu iaIn-phase or anti-phase, the range of adjustment is shown in fig. 3.
2. Bipolar Buck alternating-current unit circuit of line voltage connected by independently adjusting line voltage
When the bipolar Buck alternating-current unit circuit works on the line voltage connected with the independent regulation of the line voltage, taking a first bipolar Buck alternating-current unit circuit submodule DPFC-a as an example: the duty ratio of the A-phase bipolar Buck alternating-current unit circuit Buck-a is set by taking the A-phase bipolar Buck alternating-current unit circuit Buck-a and the BC-phase bipolar Buck alternating-current unit circuit Buck-BC as examplesd a1And is 0.5, and the output voltage of the A-phase bipolar Buck AC unit circuit Buck-a is zero. Setting the duty ratio of a BC-phase bipolar Buck alternating-current unit circuit Buck-BCd a2In [0,1 ]]In a range of regulation with an output voltage of value (2)d a2-1）u ia ,In [ -u ia,u ia]And (4) adjusting within a range. At this timeu oaIn and withu iaIs adjusted in the direction of 90 deg. difference, and the adjustment range is shown in fig. 4.
3. Phase voltage bipolar Buck alternating current unit circuit and line voltage bipolar Buck alternating current unit circuit connected with phase voltage and line voltage between two other phases and simultaneously adjusted
When the bipolar Buck alternating-current unit circuit works in a state that the phase voltage and the line voltage between the other two phases are simultaneously regulated, the bipolar Buck alternating-current unit circuit and the bipolar Buck alternating-current unit circuit of the line voltage are connected, taking a first bipolar Buck alternating-current unit circuit sub-module DPFC-a as an example: the duty ratio of the A-phase bipolar Buck alternating-current unit circuit Buck-a is set by taking the A-phase bipolar Buck alternating-current unit circuit Buck-a and the BC-phase bipolar Buck alternating-current unit circuit Buck-BC as examplesd a1In [0,1 ]]The output voltage value of the A-phase bipolar Buck AC unit circuit Buck-a is regulated within a range (at the moment)2d a1-1）u iaIn the range of [ -u ia,u ia]In the direction ofu iaThe same direction or the opposite direction; setting the duty ratio of a BC-phase bipolar Buck alternating-current unit circuit Buck-BCd a2In [0,1 ]]In a range of regulation with an output voltage of value (2)d a2-1）u iaAt right angles tou iaIn the direction of [ -u ia,u ia]And (4) adjusting within a range. At this timeu oaThe output voltage value of the A-phase bipolar Buck alternating current unit circuit Buck-a and the output voltage value of the BC-phase bipolar Buck alternating current unit circuit Buck-BC are subjected to vector synthesis, the phase angle of the vector synthesis is adjusted within a range of 360 degrees, and the amplitude of the vector synthesis is adjusted within a rectangular range. Will be provided withu oaConnected in series to the gridu iaIn the method, active power and reactive power are simultaneously provided or absorbed for the power grid, so that active power flow and reactive power flow are simultaneously regulated, and the regulation range is shown in fig. 5.
Specifically, when the bipolar Buck alternating-current unit circuit and the bipolar Buck alternating-current unit circuit of the line voltage are operated to simultaneously regulate the phase voltage and the line voltage connected between the other two phases, taking the first bipolar Buck alternating-current unit circuit sub-module DPFC-a as an example, the input voltage of the bipolar Buck alternating-current unit circuit Buck-a of the A-phase is taken asu ia=U iAsinωtThe input voltage of the BC-phase bipolar Buck alternating-current unit circuit Buck-BC isu ibc=U iBCsin(ωt-90 °). If the duty ratio of the A-phase bipolar Buck AC unit circuit Buck-a is setd a1∈[0.5.1]Setting the duty ratio of the BC-phase bipolar Buck AC unit circuit Buck-BCd a2∈[0,0.5]At this timeu oaIs in a first interval (O-F-L-J); if the duty ratio of the A-phase bipolar Buck AC unit circuit Buck-a is setd a1∈[0,0.5]Setting the duty ratio of the BC-phase bipolar Buck AC unit circuit Buck-BCd a2∈[0,0.5]At this timeu oaThe phase of (D) is within a second interval (O-J-K-D); if the duty ratio of the A-phase bipolar Buck AC unit circuit Buck-a is setd a1∈[0,0.5]A BC-phase bipolar Buck AC unit circuit Buck-b is providedc duty cycled a2∈[0.5,1]At this timeu oaThe phase of (a) is within a first interval (O-D-Q-H); if the duty ratio of the A-phase bipolar Buck AC unit circuit Buck-a is setd a1∈[0.5,1]Setting the duty ratio of the BC-phase bipolar Buck AC unit circuit Buck-BCd a2∈[0.5,1]At this timeu oaWithin a first interval (O-H-R-F).
The arrangement of the second and third bipolar Buck ac unit circuit sub-modules DPFC-b and DPFC-c may be as described with reference to the first bipolar Buck ac unit circuit sub-module DPFC-a. The duty ratio of a B-phase bipolar Buck alternating current unit circuit Buck-B in a second bipolar Buck alternating current unit circuit sub-module DPFC-B isd b1The duty ratio of the CA-phase bipolar Buck alternating-current unit circuit Buck-CA in the second bipolar Buck alternating-current unit circuit sub-module DPFC-b isd b2The duty ratio of the C-phase bipolar Buck alternating-current unit circuit Buck-C in the third bipolar Buck alternating-current unit circuit sub-module DPFC-C isd c1The duty ratio of the AB-phase bipolar Buck alternating-current unit circuit Buck-AB in the third bipolar Buck alternating-current unit circuit sub-module DPFC-c isd c2. At this timeu oa、u ob、u ocAdjustment within a range of 360 is achieved. It should be noted that, when the input voltage of the original power grid is balanced in three phases,d a1= d b1= d c1、d a2= d b2= d c2(ii) a If the three phases of the input voltage of the original power grid are unbalanced, the required voltage value and the required phase are calculated according to the specific voltage value and the specific phased a1、d b1、d c1、d a2、d b2、d c2(ii) a The adjusted grid voltage is three-phase balanced. Therefore, the power flow controller also has the capacity of adjusting the power flow under the unbalanced three-phase voltage.
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.
Claims (10)
1. A bipolar modulation 360-degree power flow controller is characterized in that the input end of the flow controller is connected into a high-voltage power grid in parallel, and the output end of the flow controller is connected into the high-voltage power grid in series, wherein: the device comprises a three-phase input transformation module, a bipolar Buck alternating current unit circuit module and an output filtering module;
the bipolar Buck alternating-current unit circuit module comprises a phase voltage bipolar Buck alternating-current unit circuit and a line voltage bipolar Buck alternating-current unit circuit, an output end of the phase voltage bipolar Buck alternating-current unit circuit is connected with an input end of the output filtering module after being connected with an output end of the line voltage bipolar Buck alternating-current unit circuit in series, an output phase voltage of the three-phase input transformation module and an output line voltage which is 90 degrees different from the phase voltage of the output phase voltage are respectively connected with the phase voltage bipolar Buck alternating-current unit circuit and the line voltage bipolar Buck alternating-current unit circuit, and 360-degree adjustment of the amplitude and the phase of the output voltage is achieved through the output filtering module;
when the phase voltage bipolar Buck alternating-current unit circuit and the line voltage bipolar Buck alternating-current unit circuit which are connected with the line voltage between the phase voltage and the other two phases are adjusted simultaneously, the phase angle of the output voltage value of the phase voltage bipolar Buck alternating-current unit circuit and the output voltage value of the line voltage bipolar Buck alternating-current unit circuit can be adjusted in a complete and continuous 360-degree range after vector synthesis is carried out on the output voltage value of the phase voltage bipolar Buck alternating-current unit circuit and the duty ratio of the line voltage bipolar Buck alternating-current unit circuit.
2. The bipolar modulated 360 ° power flow controller of claim 1, wherein: the bipolar Buck alternating-current unit circuit module comprises a first bipolar Buck alternating-current unit circuit submodule, a second bipolar Buck alternating-current unit circuit submodule and a third bipolar Buck alternating-current unit circuit submodule, wherein the first bipolar Buck alternating-current unit circuit submodule, the second bipolar Buck alternating-current unit circuit submodule and the third bipolar Buck alternating-current unit circuit submodule all comprise a phase voltage bipolar Buck alternating-current unit circuit and a line voltage bipolar Buck alternating-current unit circuit which are connected in series.
3. The bipolar modulated 360 ° power flow controller of claim 1, wherein: the three-phase output voltage transformation module is connected with the output filtering module.
4. A bipolar modulated 360 ° power flow controller according to claim 1 or 3, characterized by: the output filtering module comprises a first output filter, a second output filter and a third output filter, wherein the input end of the first output filter is connected with the output end of the first bipolar Buck alternating current unit circuit submodule; the input end of the second output filter is connected with the output end of the second bipolar Buck alternating current unit circuit submodule; and the input end of the third output filter is connected with the output end of the third bipolar Buck alternating-current unit circuit submodule.
5. The bipolar modulated 360 ° power flow controller of claim 4, wherein: the first output filter, the second output filter and the third output filter comprise output filter inductors and output filter capacitors.
6. The bipolar modulated 360 ° power flow controller of claim 1, wherein: the three-phase input transformation module comprises a first three-phase input transformer and a second three-phase input transformer, and the secondary sides of the first three-phase input transformer and the second three-phase input transformer are provided with center taps.
7. The bipolar modulated 360 ° power flow controller of claim 6, wherein: the primary side of the first three-phase input transformer is in star connection, and the secondary side of the first three-phase input transformer comprises a phase voltage output winding; and the primary side of the second three-phase input transformer is in triangular connection, and the secondary side of the second three-phase input transformer comprises a line voltage output winding.
8. The bipolar modulated 360 ° power flow controller of claim 7, wherein: and the input end of the primary side of the first three-phase input transformer and the input end of the primary side of the second three-phase input transformer are connected into the high-voltage power grid in parallel.
9. The bipolar modulated 360 ° power flow controller of claim 7, wherein: the phase voltage output winding of the first three-phase input transformer is connected with the input end of the phase voltage bipolar Buck alternating current unit circuit; and the line voltage output winding of the second three-phase input transformer is connected with the input end of the line voltage bipolar Buck alternating current unit circuit.
10. A method of operating a bipolar modulated 360 ° power flow controller according to any of claims 1-9, characterized by: the output phase voltage of the three-phase input transformation module and the output line voltage with a phase difference of 90 degrees with the output phase voltage are respectively connected with the phase voltage bipolar Buck alternating current unit circuit and the line voltage bipolar Buck alternating current unit circuit, the output voltage amplitude and the phase angle of the power flow controller are adjusted by respectively adjusting the duty ratio of the phase voltage bipolar Buck alternating current unit circuit and the line voltage bipolar Buck alternating current unit circuit, and active power flow and reactive power flow are adjusted independently or simultaneously.
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