CN112803425A - Dynamic voltage compensation device for alternating current-direct current hybrid power distribution network and control method thereof - Google Patents
Dynamic voltage compensation device for alternating current-direct current hybrid power distribution network and control method thereof Download PDFInfo
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- CN112803425A CN112803425A CN202110329690.5A CN202110329690A CN112803425A CN 112803425 A CN112803425 A CN 112803425A CN 202110329690 A CN202110329690 A CN 202110329690A CN 112803425 A CN112803425 A CN 112803425A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
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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
- H02J3/01—Arrangements for reducing harmonics or ripples
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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
- H02J3/02—Circuit arrangements for ac mains or ac distribution networks using a single network for simultaneous distribution of power at different frequencies; using a single network for simultaneous distribution of ac power and of dc power
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The invention relates to a dynamic voltage compensation device for an alternating current-direct current hybrid power distribution network and a control method thereof, wherein the device comprises: the A-phase rectification and transformation module, the B-phase rectification and transformation module and the C-phase rectification and transformation module are electrically connected with each other; a looks rectification vary voltage module, B looks rectification vary voltage module and C looks rectification vary voltage module all include: the high-voltage input side electric wiring terminal, the reactor, the power units with the input sides connected in series and the isolation transformers with the primary sides respectively electrically connected with the output sides of the power units are electrically connected in sequence; the power units at the tail ends of the A-phase rectification transformation module, the B-phase rectification transformation module and the C-phase rectification transformation module are electrically connected with each other, and the isolation transformers at the tail ends are electrically connected with each other; the outlet terminals at the input side of the power units at the tail ends are in short connection to form a high-voltage neutral point N; and a direct current bus leading-out terminal of the power unit at one tail end is used as a negative terminal at a low-voltage direct current output side and a positive terminal at the low-voltage direct current output side.
Description
Technical Field
The invention relates to the technical field of power quality control, in particular to a reconfigurable dynamic voltage compensation device for an alternating current-direct current hybrid power distribution network and a control method thereof.
Background
The power grid faults and natural disasters such as lightning stroke, short circuit, high-capacity load switching, grounding and the like can all generate transient power quality problems such as voltage sag, short-time interruption and the like, great economic losses are brought to sensitive load users such as chip processing, scientific research parks and the like, and the harmfulness of the power grid faults exceeds steady-state power quality problems such as harmonic waves, three-phase imbalance, voltage deviation and the like. At present, voltage sag and short-time interruption treatment devices mainly comprise a low-voltage Dynamic Voltage Restorer (DVR), a solid-state transfer switch (SSTS), a non-power-off power supply (UPS) and the like, and generally have the defects of complicated DVR equipment, small compensation range required by a series-connection safety factor and poor parallel-connection dynamic response; SSTS requires two-way and independent power supplies, switching logic is complex, and long power failure time occurs in the switching process; the UPS is generally applied to a small-capacity load, has a slow response speed and low efficiency, and is accompanied by power quality problems such as harmonic pollution.
On the other hand, more and more sensitive loads of a user side, such as a data center and the like, adopt direct current power distribution, a large number of current conversion links are saved, power distribution and utilization loss is effectively reduced, but the current voltage sag treatment device generally does not have a direct current output port, and the transient voltage problem treatment requirements of the occasions cannot be met.
Disclosure of Invention
The present invention is directed to solve at least one of the problems in the related art and to provide a dynamic voltage compensation apparatus for an ac/dc hybrid power distribution network and a control method thereof.
In order to achieve the above object, the present invention provides a dynamic voltage compensation device for an ac/dc hybrid power distribution network, comprising: the A-phase rectification and transformation module, the B-phase rectification and transformation module and the C-phase rectification and transformation module are electrically connected with each other;
the A-phase rectification transformation module, the B-phase rectification transformation module and the C-phase rectification transformation module all comprise: the high-voltage input side electric wiring terminal, the reactor, the power units with the input sides connected in series and the isolation transformer with the primary sides respectively electrically connected with the output sides of the power units are electrically connected in sequence;
the power units at the tail ends of the A-phase rectification transformation module, the B-phase rectification transformation module and the C-phase rectification transformation module are electrically connected with each other, and the isolation transformers at the tail ends are electrically connected with each other;
the outlet terminals at the input side of the power units at the tail ends are in short connection to form a high-voltage neutral point N;
the direct current bus leading-out terminal of any one tail end of the power unit is used as a negative connecting terminal of a low-voltage direct current output side and a positive connecting terminal of the low-voltage direct current output side;
and after being connected, the isolation transformers in the A-phase rectification transformation module, the B-phase rectification transformation module and the C-phase rectification transformation module are respectively led out of a low-voltage alternating-current output side neutral point n electric wiring terminal and a low-voltage alternating-current output side electric wiring terminal.
According to one aspect of the invention, the secondary side of each isolation transformer in the A-phase rectification transformation module, the B-phase rectification transformation module and the C-phase rectification transformation module is connected in parallel, and then a low-voltage alternating-current output side neutral point n electric wiring terminal and a low-voltage alternating-current output side electric wiring terminal are led out.
According to one aspect of the invention, the secondary sides of the isolation transformers in the a-phase rectification and transformation module, the B-phase rectification and transformation module and the C-phase rectification and transformation module are connected in series and then lead out a low-voltage alternating-current output side neutral point n electrical connection terminal and a low-voltage alternating-current output side electrical connection terminal.
According to an aspect of the invention, the power unit comprises: the high-voltage direct-current power supply comprises an input side H bridge left upper bridge arm IGBT and an anti-parallel diode thereof, an input side H bridge right upper bridge arm IGBT and an anti-parallel diode thereof, an input side H bridge left lower bridge arm IGBT and an anti-parallel diode thereof, an input side H bridge right lower bridge arm IGBT and an anti-parallel diode thereof, an output side H bridge left upper bridge arm IGBT and an anti-parallel diode thereof, an output side H bridge left lower bridge arm IGBT and an anti-parallel diode thereof, an output side H bridge right lower bridge arm IGBT and an anti-parallel diode thereof, an input side bypass switch, an output side series switch, an output side parallel switch and a direct-current capacitor arranged between the input side H bridge and the output side H bridge.
According to one aspect of the invention, the dc capacitor is a supercapacitor bank.
In order to achieve the above object, the present invention further provides a control method for a dynamic voltage compensation apparatus for an ac/dc hybrid power distribution network, including:
the input end controls: the input side power units of an A-phase H bridge, a B-phase H bridge and a C-phase H bridge are equivalent to three-phase alternating current voltage sources with controllable amplitude and frequency for control, and two control targets of the input side three-phase H bridge current converter are respectively as follows: one of them ensures constant voltage on the AC side, passes through U1rms=U* 1rmsThe realization that the voltage of the direct current capacitor is constant is ensured through Udc=U* dcThe implementation is carried out;
to output target voltage instruction value Ud1And Uq1Carrying out two-phase rotation-three-phase static coordinate transformation to obtain a reference voltage modulation wave Ux of the three-phase voltage source convertera1、U*b1And Uc1Then outputting PWM waveforms required by all three-phase power units through a CPS-PWM modulation module, wherein the PWM waveforms control IGBT devices on the input side;
and (3) output end control: the output sides of an A-phase H bridge, a B-phase H bridge and a C-phase H bridge are equivalent to three-phase alternating current voltage sources with controllable amplitude and frequency to be controlled, and the control targets of the output-side three-phase H bridge current converter are as follows: maintaining the amplitude and frequency of the AC bus voltage of the output sensitive load constant by controlling Ud2=√2U*2rms,Uq2Can be realized by =0, U2rmsThe amplitude of the working voltage required by the normal work of the sensitive load;
target voltage value Ud2And Uq2By two-phase rotation-three-phase standstillCoordinate transformation is carried out to obtain a reference voltage modulation wave U of the H-bridge output end voltage source convertera2、U*b2And Uc2Then outputting PWM waveforms required by all three-phase power units through a CPS-PWM module, wherein the PWM waveforms control IGBT devices on the input side;
in the formula of Ud1And Uq1D-axis and q-axis voltage components after three-phase static-two-phase rotation coordinate transformation are carried out on the three-phase alternating current voltage of the electric node; u shaped2And Uq2And d-axis voltage components and q-axis voltage components after three-phase static-two-phase rotation coordinate transformation are respectively carried out on the three-phase alternating-current voltage of the electric node.
According to one aspect of the invention, the two-phase rotation-three-phase stationary coordinate transformation matrix is formulated as:
where θ is the phase of the node voltage in degrees.
According to the scheme of the invention, the direct current capacitor of the device adopts the high-capacity super capacitor, when the voltage at the system side has a temporary drop and drop fault, the energy of the direct current capacitor maintains the amplitude and the frequency of the alternating current voltage at the output side constant in a short time, and the power utilization safety of the sensitive load is ensured, so that the temporary drop and the drop problem at the system side cannot influence the sensitive load, and the working mode of the device has no switching process, so that the device has no switching time.
The device has rich interfaces and flexible wiring, can be connected with direct current sensitive loads, can also be connected with alternating current sensitive loads, can be connected with three-phase alternating current loads, and can also be connected with single-phase alternating current loads, so that the device is very suitable for an alternating current-direct current hybrid power distribution network with a large number of sensitive loads.
The device of the invention realizes high-low voltage grade conversion, saves a large-capacity distribution transformer, improves the efficiency, and saves investment and occupied land.
The device not only completes the functions of transient voltage sag, drop compensation and voltage conversion, but also stabilizes the voltage of the alternating current high-voltage side through the dynamic reactive power compensation of the power grid side, and simultaneously can realize the harmonic suppression of a certain frequency of the power grid by slightly changing the control strategy, thereby playing the role of improving the power quality of the power grid.
The device has a redundancy function, when the interior of the power unit has a fault, the power unit is quitted from the system by controlling the switching of the input side and the output side of the power unit, and other power units continue to work, so that the reliability and the safety of the system operation are improved.
The switch in the device is an electronic mechanical composite switch, seamless switching is realized, and arc discharge is avoided.
Drawings
One or more embodiments are illustrated by way of example in the accompanying drawings, which correspond to the figures in which like reference numerals refer to similar elements and which are not to scale unless otherwise specified.
Fig. 1 is a schematic diagram of main wiring of a reconfigurable dynamic voltage compensation device for an ac/dc hybrid power distribution network according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a main wiring diagram of a reconfigurable dynamic voltage compensation device for an ac/dc hybrid power distribution network according to another embodiment of the present invention;
FIG. 3 schematically illustrates a main wiring diagram of a power cell according to an embodiment of the present invention;
fig. 4 is a diagram schematically illustrating an input terminal control method of a dynamic voltage compensation apparatus for an ac/dc hybrid power distribution network according to an embodiment of the present invention;
fig. 5 is a diagram schematically illustrating an output terminal control method of a dynamic voltage compensation apparatus for an ac/dc hybrid power distribution network according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the scope of the present invention.
Fig. 1 schematically shows a main wiring diagram of a reconfigurable dynamic voltage compensation device for an ac/dc hybrid power distribution network according to an embodiment of the present invention. Fig. 2 schematically shows a main wiring diagram of a reconfigurable dynamic voltage compensation device for an ac/dc hybrid power distribution network according to another embodiment of the present invention. As shown in fig. 1 and 2, the dynamic voltage compensation apparatus for an ac/dc hybrid power distribution network according to the present invention includes: the system comprises an A-phase rectification transformation module, a B-phase rectification transformation module and a C-phase rectification transformation module which are electrically connected with each other. As shown in fig. 1 and 2, in the present invention, each of the a-phase rectification transformation module, the B-phase rectification transformation module, and the C-phase rectification transformation module includes: the high-voltage input side electric wiring terminal, the reactor, the power units with the input sides connected in series and the isolation transformer with the primary sides respectively electrically connected with the output sides of the power units are electrically connected in sequence.
According to one embodiment of the present invention, the power units at the respective ends of the a-phase rectification transformation module, the B-phase rectification transformation module, and the C-phase rectification transformation module are electrically connected to each other, and the isolation transformers at the respective ends are electrically connected to each other; the outlet terminals at the input side of the power units at the tail ends are in short connection to form a high-voltage neutral point N; the direct current bus leading-out terminal of any one power unit at the tail end is used as a negative connecting terminal of a low-voltage direct current output side and a positive connecting terminal of the low-voltage direct current output side; and after being connected, the isolation transformers in the A-phase rectification transformation module, the B-phase rectification transformation module and the C-phase rectification transformation module are respectively led out of a low-voltage alternating-current output side neutral point n electric wiring terminal and a low-voltage alternating-current output side electric wiring terminal.
According to the above arrangement, specifically, as shown in fig. 1 and 2, in the present embodiment, the specific arrangement of the a-phase rectification and transformation module, the B-phase rectification and transformation module, and the C-phase rectification and transformation module is as follows: an a-phase high-voltage input side electric connection terminal 1, a B-phase high-voltage input side electric connection terminal 2, a C-phase high-voltage input side electric connection terminal 3, an a-phase connected reactor 4, a B-phase connected reactor 5, a C-connected reactor 6, an a-phase 1 st power unit 7, an a-phase 1 st isolation transformer 8, a B-phase 1 st power unit 9, a B-phase 1 st isolation transformer 10, a C-phase 1 st power unit 11, a C-phase 1 st isolation transformer 12, an a-phase 2 nd power unit 1, an a-phase 2 nd isolation transformer 14, a B-phase 2 nd power unit 15, a B-phase 2 nd isolation transformer 16, a C-phase 2 nd power unit 17, a C-phase 2 nd isolation transformer 18, an a-phase nth power unit 19, an a-phase nth isolation transformer 20, a-phase nth power unit 21, a B-phase nth isolation transformer 22, a C-phase nth power unit 23, a, A C-phase nth isolation transformer 24, a low-voltage dc output side negative terminal 25, a low-voltage dc output side positive terminal 26, a low-voltage ac output side neutral point n electrical terminal 27, a low-voltage ac output side a-phase electrical terminal 28, a low-voltage ac output side b-phase electrical terminal 29, and a low-voltage ac output side C-phase electrical terminal 30.
Fig. 3 schematically shows a main wiring diagram of a power cell according to an embodiment of the present invention. As shown in fig. 3, in the present embodiment, the internal device composition and the electrical wiring of the power units 7, 9, 11, 13, 15, 17, 19, 21, and 23 are completely the same, and each power unit includes: an input side H bridge left upper arm IGBT and an anti-parallel diode 31 thereof, an input side H bridge right upper arm IGBT and an anti-parallel diode 32 thereof, an input side H bridge left lower arm IGBT and an anti-parallel diode 33 thereof, an input side H bridge right lower arm IGBT and an anti-parallel diode 34 thereof, a direct current capacitor 35, an output side H bridge left upper arm IGBT and an anti-parallel diode 36 thereof, an output side H bridge right upper arm IGBT and an anti-parallel diode 37 thereof, an output side H bridge left lower arm IGBT and an anti-parallel diode 38 thereof, an output side H bridge right lower arm IGBT and an anti-parallel diode 39 thereof, an input side bypass switch 40, an output side series switch 41 and an output side parallel switch 42.
According to the arrangement of the invention, in operation, the A-phase high-voltage input side electric wiring terminal 1 is connected into an A-phase H-bridge series power unit group consisting of the power units 7, 13 and 19 through the connecting reactor 4. The input sides of the power units 7, 13 and 19 are connected in series, the output sides are respectively connected to the primary sides of the isolation transformers 8, 14 and 20, and the secondary sides of the isolation transformers 8, 14 and 20 are respectively led out of a low-voltage alternating-current output side neutral point n electric wiring terminal 27 and a low-voltage alternating-current output side a-phase electric wiring terminal 28 after being connected in parallel (as shown in figure 1) or in series (as shown in figure 2).
The B-phase high-voltage input side electric wiring terminal 2 is connected into a B-phase H-bridge series power unit group consisting of power units 9, 15 and 21 through a connecting reactor 5. The input sides of the power units 9, 15 and 21 are connected in series, the output sides are respectively connected with the primary sides of the isolation transformers 10, 16 and 22, and the secondary sides of the isolation transformers 10, 16 and 22 are respectively led out of a low-voltage alternating-current output side neutral point n electric wiring terminal 27 and a low-voltage alternating-current output side b-phase electric wiring terminal 29 after being connected in parallel (as shown in figure 1) or in series (as shown in figure 2).
The C-phase high-voltage input side electric wiring terminal 3 is connected to a C-phase H-bridge series power unit group consisting of power units 11, 17 and 23 through a connecting reactor 6. The input sides of the power units 11, 17 and 23 are connected in series, the output sides are respectively connected to the primary sides of the isolation transformers 12, 18 and 24, and the secondary sides of the isolation transformers 12, 18 and 24 are respectively led out of a low-voltage alternating-current output side neutral point n electric wiring terminal 27 and a low-voltage alternating-current output side c-phase electric wiring terminal 30 after being connected in parallel (as shown in figure 1) or in series (as shown in figure 2).
The ac single-phase load is distributed between the electrical connection terminal 27 and the electrical connection terminal 28, or between the electrical connection terminal 27 and the electrical connection terminal 29, or between the electrical connection terminal 27 and the electrical connection terminal 30, and the ac three-phase load is distributed between the electrical connection terminals 27, 28, 29, and 30.
The input measuring line terminals of the power units 19, 21, 23 are short-circuited together to form a high-voltage neutral point N. The dc bus bar lead terminals of the power unit 19 are a low-voltage dc output side negative electrode terminal 25 and a low-voltage dc output side positive electrode terminal 26. The dc load is connected between the low-voltage dc output side negative electrode terminal 25 and the low-voltage dc output side positive electrode terminal 26.
The direct current capacitor 35 adopts a super capacitor bank, the stored energy can ensure that the voltage value of the sensitive load side is kept constant in a short time under the conditions of voltage sag and short-time interruption fault on the system side, and the time length can be from millisecond level to minute level according to actual needs.
Normally, the input side bypass switch 40 and the output side bypass switch 42 are in an open state, and the output side series switch 41 is in a closed state.
As shown in fig. 1, when a fault occurs inside a power unit, the input side bypass switch 40 is closed, and the output side series switch 41 is opened, so that the fault power unit exits the system, and the operation does not affect the normal operation of other power units.
As shown in fig. 2, when a fault occurs inside the power unit, the input side bypass switch 40 is closed, the output side series switch 41 is opened, and the output side bypass switch 42 is closed, so that the faulty power unit is removed from the system, and the above operations do not affect the normal operation of other power units.
Fig. 4 is a diagram schematically illustrating an input terminal control method of a dynamic voltage compensation apparatus for an ac/dc hybrid power distribution network according to an embodiment of the present invention. Fig. 5 is a diagram schematically illustrating an output terminal control method of a dynamic voltage compensation apparatus for an ac/dc hybrid power distribution network according to an embodiment of the present invention. As shown in fig. 4 and 5, in the present invention, as shown in fig. 4, the input terminal control method is: and the input side power modules of the A-phase H bridge, the B-phase H bridge and the C-phase H bridge are equivalent to three-phase alternating current voltage sources with controllable amplitude and frequency for control. Wherein L1 in FIG. 4 is the inductive reactance value of the connecting reactors 4, 5, 6, ω is the angular frequency (2 × π × f), UdcIs the average value of the voltage of the DC capacitor 35 inside all the power cells, U1rmsId1 and iq1 are d-axis and q-axis current components obtained by three-phase static-two-phase rotation coordinate transformation of three-phase alternating current passing through the electric nodes 1, 2 and 3, and U is the three-phase average value of the effective value of the alternating voltage of the electric nodes 1, 2 and 3d1And Uq1And d-axis and q-axis voltage components after three-phase static-two-phase rotation coordinate transformation are carried out on the three-phase alternating voltages of the electric nodes 1, 2 and 3. Two control targets of the input-side three-phase H-bridge converter are respectively as follows:one of them ensures constant voltage on the AC side, passes through U1rms=U* 1rmsImplementation, which ensures constant DC-side capacitor 35 voltage, via Udc=U* dcAnd (5) realizing. The data are regulated by two sets of PI (proportional integral) of an inner ring and an outer ring of a dotted line frame in the graph 4, and then a target voltage instruction value U is outputd1And Uq1. To Ud1And Uq1Carrying out two-phase rotation-three-phase static coordinate transformation to obtain a reference voltage modulation wave Ux of the three-phase voltage source convertera1、U*b1And Uc1And outputting PWM waveforms required by all three-phase power units through a CPS-PWM modulation module, wherein PWM11, PWM12, PWM13 and PWM14 respectively control four IGBT devices on the input side of the power unit 7, PWM21, PWM22, PWM23 and PWM24 respectively control four IGBT devices on the input side of the power unit 13, and so on.
As shown in fig. 5, the output side of the a-phase H-bridge, the B-phase H-bridge, and the C-phase H-bridge is also equivalent to a three-phase ac voltage source with controllable amplitude and frequency for controlling. L2 in FIG. 5 is the leakage reactance value, U, of each isolation transformerd2And Uq2D-axis and q-axis voltage components, I, after three-phase static-two-phase rotation coordinate transformation of three-phase alternating voltages of the electric nodes 28, 29 and 30 respectivelyd2And Iq2The d-axis and q-axis current components are obtained by converting three-phase stationary-two-phase rotational coordinates of three-phase ac currents passing through the electrical nodes 28, 29, and 30. The control targets of the output-side three-phase H-bridge converter are as follows: maintaining the amplitude and frequency of the AC bus voltage of the output sensitive load constant by controlling Ud2=√2U*2rms,Uq2Can be realized by =0, U2rmsThe amplitude of the working voltage is required for the normal work of the sensitive load. The data is regulated by two sets of PI of the outer ring and the inner ring in the dotted line frame of FIG. 5, and then a target voltage command value U is outputd2And Uq2. Target voltage value Ud2And Uq2Obtaining a reference voltage modulation wave U of the voltage source converter at the output end of the H bridge through two-phase rotation-three-phase static coordinate transformationa2、U*b2And Uc2And then outputting PWM waveforms required by all three-phase power units through a CPS-PWM module, whereinThe PWM11, the PWM12, the PWM13 and the PWM14 respectively control four IGBT devices on the output side of the power unit 7, the PWM21, the PWM22, the PWM23 and the PWM24 respectively control four IGBT devices on the output side of the power unit 13, and so on.
In the present embodiment, as described above, the control method of the apparatus according to the present invention employs the D, Q decoupling control algorithm based on the rotational coordinate transformation. The three-phase static-two-phase rotating coordinate transformation matrix is shown in a formula (1), the two-phase rotating-three-phase static coordinate transformation matrix is shown in a formula (2), and theta is the phase of the voltage of the node 1 and the unit is an angle.
In this embodiment, the power unit uses carrier phase-shift SPWM modulation (CPS-SPWM), i.e., a set of triangular carriers uniformly distributed in phase is used to compare with a sinusoidal modulation signal to generate multiple PWM signals for driving the switching device. CPS-SPWM can make the output waveforms of the cascaded H bridges consistent, and each H bridge can realize higher equivalent switching frequency of the whole device under lower switching frequency, thereby achieving the purposes of reducing the switching frequency and switching loss of devices and reducing harmonic waves at the same time, for example, if the number of the cascaded H bridges N =7, the triangular carrier frequency is 1kHz, if a single-pole frequency multiplication CPS-SPWM modulation technology is adopted, the equivalent switching frequency obtained by each phase is 7 x 2 x 1=14kHz, and the seed feeding effect is more obvious along with the increase of the number N of the cascaded H bridges.
According to the scheme of the invention, the direct-current capacitor of the device adopts the high-capacity super capacitor, when the voltage at the system side has a temporary drop and drop fault, the energy of the direct-current capacitor maintains the amplitude and the frequency of the alternating-current voltage at the output side constant in a short time, and the power utilization safety of the sensitive load is ensured, so that the temporary drop and the drop of the system side cannot influence the sensitive load, and the working mode of the device has no switching process and no switching time.
The device has rich interfaces and flexible wiring, can be connected with direct current sensitive loads, can also be connected with alternating current sensitive loads, can be connected with three-phase alternating current loads, and can also be connected with single-phase alternating current loads, so that the device is very suitable for an alternating current-direct current hybrid power distribution network with a large number of sensitive loads.
The device of the invention realizes high-low voltage grade conversion, saves a large-capacity distribution transformer, improves the efficiency, and saves investment and occupied land.
The device not only completes the functions of transient voltage sag, drop compensation and voltage conversion, but also stabilizes the voltage of the alternating current high-voltage side through the dynamic reactive power compensation of the power grid side, and simultaneously can realize the harmonic suppression of a certain frequency of the power grid by slightly changing the control strategy, thereby playing the role of improving the power quality of the power grid.
The device has a redundancy function, when the interior of the power unit has a fault, the power unit is quitted from the system by controlling the switching of the input side and the output side of the power unit, and other power units continue to work, so that the reliability and the safety of the system operation are improved.
The switches 40 and 41 in the device are electronic mechanical composite switches, seamless switching is realized, and arc discharge is avoided.
The key point of the device is the unified coordination control of the reactive power at the input side, the active power at the direct current side and the voltage and current at the output side of the system, so that the stable operation of the device is realized.
The device can realize the reconstruction of the output voltage and current grade of the alternating current side by changing the parallel connection of the output side alternating current transformers into the series connection or changing the series connection into the parallel connection.
Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.
Claims (7)
1. A dynamic voltage compensation device for alternating current-direct current hybrid power distribution network, its characterized in that includes: the A-phase rectification and transformation module, the B-phase rectification and transformation module and the C-phase rectification and transformation module are electrically connected with each other;
the A-phase rectification transformation module, the B-phase rectification transformation module and the C-phase rectification transformation module all comprise: the high-voltage input side electric wiring terminal, the reactor, the power units with the input sides connected in series and the isolation transformer with the primary sides respectively electrically connected with the output sides of the power units are electrically connected in sequence;
the power units at the tail ends of the A-phase rectification transformation module, the B-phase rectification transformation module and the C-phase rectification transformation module are electrically connected with each other, and the isolation transformers at the tail ends are electrically connected with each other;
the outlet terminals at the input side of the power units at the tail ends are in short connection to form a high-voltage neutral point N;
the direct current bus leading-out terminal of any one tail end of the power unit is used as a negative connecting terminal of a low-voltage direct current output side and a positive connecting terminal of the low-voltage direct current output side;
and after being connected, the isolation transformers in the A-phase rectification transformation module, the B-phase rectification transformation module and the C-phase rectification transformation module are respectively led out of a low-voltage alternating-current output side neutral point n electric wiring terminal and a low-voltage alternating-current output side electric wiring terminal.
2. The dynamic voltage compensation device for the ac/dc hybrid power distribution network according to claim 1, wherein the secondary sides of the isolation transformers in the a-phase rectification transformation module, the B-phase rectification transformation module and the C-phase rectification transformation module are connected in parallel to lead out a low-voltage ac output side neutral point n electrical connection terminal and a low-voltage ac output side electrical connection terminal.
3. The dynamic voltage compensation device for the ac/dc hybrid power distribution network according to claim 1, wherein the secondary sides of the isolation transformers in the a-phase rectification and transformation module, the B-phase rectification and transformation module, and the C-phase rectification and transformation module are connected in series to lead out a low-voltage ac output side neutral point n electrical connection terminal and a low-voltage ac output side electrical connection terminal.
4. The dynamic voltage compensation device of claim 1, wherein the power unit comprises: the high-voltage direct-current power supply comprises an input side H bridge left upper bridge arm IGBT and an anti-parallel diode thereof, an input side H bridge right upper bridge arm IGBT and an anti-parallel diode thereof, an input side H bridge left lower bridge arm IGBT and an anti-parallel diode thereof, an input side H bridge right lower bridge arm IGBT and an anti-parallel diode thereof, an output side H bridge left upper bridge arm IGBT and an anti-parallel diode thereof, an output side H bridge left lower bridge arm IGBT and an anti-parallel diode thereof, an output side H bridge right lower bridge arm IGBT and an anti-parallel diode thereof, an input side bypass switch, an output side series switch, an output side parallel switch and a direct-current capacitor arranged between the input side H bridge and the output side H bridge.
5. The dynamic voltage compensation device of claim 4, wherein the DC capacitor is a super capacitor bank.
6. The control method for the dynamic voltage compensation device for the ac/dc hybrid power distribution network according to any one of claims 1 to 5, comprising:
the input end controls: the input side power units of an A-phase H bridge, a B-phase H bridge and a C-phase H bridge are equivalent to three-phase alternating current voltage sources with controllable amplitude and frequency for control, and two control targets of the input side three-phase H bridge current converter are respectively as follows: one of them ensures constant voltage on the AC side, passes through U1rms=U* 1rmsThe realization that the voltage of the direct current capacitor is constant is ensured through Udc=U* dcThe implementation is carried out;
for output target voltage instruction value U* d1And U* q1Two-phase rotation-three-phase static coordinate transformation is carried out to obtain threeReference voltage modulation wave instruction value U of phase voltage source converter* a1、U* b1And U* c1Then outputting PWM waveforms required by all three-phase power units through a CPS-PWM modulation module, wherein the PWM waveforms control IGBT devices on the input side;
and (3) output end control: the output sides of an A-phase H bridge, a B-phase H bridge and a C-phase H bridge are equivalent to three-phase alternating current voltage sources with controllable amplitude and frequency to be controlled, and the control targets of the output-side three-phase H bridge current converter are as follows: maintaining the amplitude and frequency of the AC bus voltage of the output sensitive load constant by controlling Ud2=√2U* 2rms,Uq2Can be realized by =0, U* 2rmsThe amplitude of the working voltage required by the normal work of the sensitive load;
target voltage value U* d2And U* q2Obtaining a reference voltage modulation wave instruction U of the voltage source converter at the output end of the H bridge through two-phase rotation-three-phase static coordinate transformation* a2、U* b2And U* c2Then outputting PWM waveforms required by all three-phase power units through a CPS-PWM module, wherein the PWM waveforms control IGBT devices on the input side;
in the formula of Ud1And Uq1D-axis and q-axis voltage components after three-phase static-two-phase rotation coordinate transformation are carried out on the three-phase alternating current voltage of the electric node; u shaped2And Uq2And d-axis voltage components and q-axis voltage components after three-phase static-two-phase rotation coordinate transformation are respectively carried out on the three-phase alternating-current voltage of the electric node.
7. The control method according to claim 6, wherein the two-phase rotation-three-phase stationary coordinate transformation matrix is formulated as:
where θ is the phase of the node voltage in degrees.
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