CN113556051A - Series-parallel hybrid connection power electronic transformer and control system - Google Patents
Series-parallel hybrid connection power electronic transformer and control system Download PDFInfo
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- CN113556051A CN113556051A CN202110824335.5A CN202110824335A CN113556051A CN 113556051 A CN113556051 A CN 113556051A CN 202110824335 A CN202110824335 A CN 202110824335A CN 113556051 A CN113556051 A CN 113556051A
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- 239000003990 capacitor Substances 0.000 claims abstract description 18
- 238000002955 isolation Methods 0.000 claims description 7
- 230000010363 phase shift Effects 0.000 claims description 7
- 230000002457 bidirectional effect Effects 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 3
- 238000004146 energy storage Methods 0.000 abstract description 7
- 238000010586 diagram Methods 0.000 description 9
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal 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
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal 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
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal 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 in a bridge configuration
-
- 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
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
- H02M1/126—Arrangements for reducing harmonics from ac input or output using passive filters
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/14—Arrangements for reducing ripples from dc input or output
-
- 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
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
Abstract
The invention discloses a series-parallel hybrid connection power electronic transformer and a control system, belonging to the field of transformers.A series-parallel hybrid connection is adopted in the power electronic transformer, each phase of a medium-voltage three-phase current-intersecting side adopts a mode of serially connecting AC/DC submodules, and on a low-voltage direct current side, firstly, each phase in a three-phase system is respectively provided with one AC/DC submodule to be serially connected, and then, each three-phase AC/DC module is parallelly connected; because the three output-side submodules are connected in series for output, the input three-phase power can be mutually supplemented at the output side, so that the input-side capacitor Cin and the output-side Cout do not need large capacitance values, only high-frequency switch ripples need to be filtered, and power-frequency ripples do not need to be filtered. Therefore, the volume of the energy storage capacitor in the module is reduced, and the power density and the reliability of the power electronic transformer are improved.
Description
Technical Field
The invention relates to the field of power electronic transformers, in particular to a series-parallel hybrid connection power electronic transformer and a control system.
Background
At present, a Power Electronic Transformer (PET for short) adopts a Power Electronic converter technology to realize electric energy conversion and electrical isolation. Compared with the traditional distribution transformer, the power electronic transformer can realize active control of power flow, and is beneficial to miniaturization and cost saving of the device.
In order to be compatible with the functions of conventional distribution transformers, the primary side of a power electronic transformer is usually connected to a medium-voltage alternating-current power grid, typically a minimum of 10kV/50Hz three-phase alternating-current power grid, and the low-voltage side can be connected to a direct-current or alternating-current power grid as required.
A typical power electronic transformer is shown in fig. 1, in which the most central part is the part for converting three-phase medium-voltage ac power into low-voltage dc power. The medium voltage side of the scheme of fig. 1 is connected in series to bear higher voltage, and the low voltage dc side is connected in parallel to provide high current. Therefore, one side of each module is single-phase alternating current, and the other side is direct current, and an H bridge and DAB two parts form a basic module in the figure 1. Fig. 2 shows an AC/DC power electronic transformer in which 1 phase is the same as the other 2 phases.
Because the power of the alternating current is pulsating in a steady state, and the power of the direct current side is kept unchanged, in order to keep the input power and the output power matched, a certain energy storage element needs to be configured inside each module, and the size of the stored energy is related to the frequency of the alternating current. Generally, power frequency 50Hz alternating current is adopted, the power pulse frequency of the alternating current is 100Hz, more capacitors are generally required to be arranged between an H bridge and DAB for energy storage, and the energy storage capacitors are large in size and poor in reliability, so that the power density and reliability of the power electronic transformer are not improved.
Therefore, a new power electronic transformer constructed by three-phase modules is needed to reduce the energy storage capacitance in the modules.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a series-parallel hybrid connection power electronic transformer and a control system, which can solve the problem of high operation cost.
The design principle is as follows: for a three-phase alternating current system, when three-phase power is balanced, the sum of the three-phase power is kept unchanged, and at the time, the sum of the three-phase power is matched with the direct current power, energy storage can be omitted theoretically inside the module, and filtering can be performed only on switching ripples in practical application. Therefore, a new AC/DC power electronic transformer structure is designed, the module combination mode in the traditional power electronic transformer is modified, and series-parallel hybrid connection is adopted.
The design scheme is as follows: the general design scheme of the application is that a module combination mode in the power electronic transformer adopts series-parallel hybrid connection, each phase of a medium-voltage three-phase current-intersecting side still adopts a mode of serially connecting AC/DC submodules, but on a low-voltage direct-current side, one AC/DC submodule is firstly taken for each phase in a three-phase system to be serially connected, the three AC/DC submodules form a new three-phase AC/DC module, and then each three-phase AC/DC module is parallelly connected.
One of the purposes of the invention is realized by adopting the following technical scheme:
a series-parallel hybrid connected power electronic transformer comprising a medium voltage three-phase AC side and a low voltage DC side connected by a plurality of three phase AC/DC modules, each three phase AC/DC module having 3 independent medium voltage AC ports and 1 low voltage DC port;
on the medium-voltage three-phase alternating current side, each phase of a three-phase AC/DC module serves as an AC/DC submodule, and 3 AC/DC submodules of each three-phase AC/DC module are respectively connected into a three-phase medium-voltage alternating current port through an inductor and are connected into a medium-voltage alternating current power supply network through each medium-voltage alternating current port through corresponding 1 medium-voltage alternating current port;
and on the low-voltage direct-current side, after each AC/DC sub-module of the three-phase AC/DC module is connected in series, each three-phase AC/DC module is connected in parallel, namely, the low-voltage direct-current side is formed by connecting all the low-voltage direct-current ports in parallel and is used for accessing a low-voltage direct-current output power grid.
Preferably, each three-phase AC/DC module includes an input side H-bridge, an electrical isolation element, and an output side H-bridge, each input side H-bridge including an input side capacitor Cin, 4 input side switches Q1-Q4, and an input side inductor Lk, each output side H-bridge including 4 output side switches Q6-Q8, and an output side capacitor Cout; because the output side AC/DC sub-modules adopt a series output mode, and the input three-phase power can be complemented at the output side, the input side capacitor Cin and the output side capacitor Cout do not need to adopt large capacitance value capacitors, only need to filter high-frequency switch ripples, and do not need to filter power frequency ripples.
Preferably, the input side switches Q1-Q4 adopt bidirectional switches to realize bidirectional power flow; the output-side switches Q5-Q8 use insulated gate bipolar transistors IGBTs.
Preferably, the electrical isolation element is a high-frequency transformer.
The invention also discloses a three-phase AC/DC power supply control system, which comprises a power electronic transformer consisting of a plurality of three-phase AC/DC modules, wherein the input side of the power electronic transformer is connected with a medium-voltage alternating-current power supply network, the three-phase alternating-current phase of the medium-voltage alternating-current power supply network is obtained through a phase-locked loop, the phase distribution of medium-voltage alternating-current voltage is carried out on each three-phase AC/DC module through a phase distributor, and a multi-level effect is generated on the medium-voltage three-phase alternating-current side by adopting a phase-shifting PWM mode among each three-phase AC/DC module.
Preferably, the driving signal of the medium-voltage three-phase current-intersecting side of the three-phase AC/DC module is generated according to the phase, so as to drive the input side switch; the low voltage DC side of the three phase AC/DC module is power controlled to obtain a low voltage drive signal.
Preferably, the low-voltage DC side is controlled by primary-secondary side phase shift, and when the power flows from the high-voltage side to the low-voltage side, the phase of the PWM signal at the low-voltage side lags behind the phase of the PWM signal at the high-voltage side by a phase angle
Thereby controlling the phase shift angle
And the control of the output power is realized.
Compared with the prior art, the invention has the beneficial effects that: the power electronic transformer adopts series-parallel hybrid connection, each phase of a medium-voltage three-phase current-intersecting side still adopts a mode of serially connecting AC/DC submodules, but on a low-voltage direct-current side, one AC/DC submodule is taken for each phase in a three-phase system to be serially connected, the three AC/DC submodules form a new three-phase AC/DC module, and then each three-phase AC/DC module is parallelly connected; because the three output-side submodules are connected in series for output, the input three-phase power can be complemented at the output side, so that the input-side capacitor Cin and the output-side Cout do not need large capacitance values, only high-frequency switch ripples need to be filtered, and power-frequency ripples do not need to be filtered. Therefore, the volume of the energy storage capacitor in the module is reduced, and the power density and the reliability of the power electronic transformer are improved.
Drawings
Fig. 1 is a schematic structural diagram of a conventional power electronic transformer;
FIG. 2 is a schematic diagram of a conventional single-phase AC/DC power electronic transformer;
FIG. 3 is a schematic diagram of a series-parallel hybrid connection-based power electronic transformer according to the present invention;
FIG. 4 is a schematic interface diagram of a three-phase AC/DC module;
FIG. 5 is a schematic diagram of a main circuit structure of a three-phase AC/DC module;
FIG. 6 is a schematic diagram of a bi-directional switch;
FIG. 7 is a schematic diagram of a control system;
FIG. 8 is a schematic of a three-phase input voltage waveform on the medium voltage three-phase current side;
FIG. 9 is a schematic diagram of a three-phase voltage chopped waveform;
fig. 10 is a diagram illustrating a corresponding relationship between output voltage, current and phase shift value.
Detailed Description
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following preferred embodiments are described in detail with reference to the accompanying drawings. It should be noted that, without conflict, any combination between the embodiments or technical features described below may form a new embodiment.
Example one
A series-parallel hybrid connected power electronic transformer, see fig. 3-6, comprises a medium voltage three-phase AC/DC side and a low voltage DC side connected by a plurality of three-phase AC/DC modules, each three-phase AC/DC module having 3 independent medium voltage AC ports and 1 low voltage DC port.
On the medium-voltage three-phase alternating current side, each phase of the three-phase AC/DC module serves as an AC/DC sub-module, 3 AC/DC sub-modules of each three-phase AC/DC module are respectively connected into the three-phase medium-voltage alternating current port through inductors and are connected into a medium-voltage alternating current power supply network through the medium-voltage alternating current ports by corresponding 1 medium-voltage alternating current port.
And on the low-voltage direct-current side, after each AC/DC sub-module of the three-phase AC/DC module is connected in series, each three-phase AC/DC module is connected in parallel, namely, the low-voltage direct-current side is formed by connecting all the low-voltage direct-current ports in parallel and is used for accessing a low-voltage direct-current output power grid.
Further, referring to fig. 5, each three-phase AC/DC module includes an input side H-bridge, each input side H-bridge including an input side capacitor Cin, 4 input side switches Q1-Q4, and an input side inductor Lk, an electrical isolation element, and an output side H-bridge, each output side H-bridge including 4 output side switches Q6-Q8, and an output side capacitor Cout.
The input side switches Q1-Q4 adopt two bidirectional switches shown in fig. 6a or fig. 6b in fig. 6 to realize bidirectional power flow.
The output side switches Q5-Q8 use insulated gate bipolar transistors IGBT.
Wherein, the electrical isolation element adopts a high-frequency transformer T.
It can be seen from the figure that, because the output side AC/DC sub-modules adopt a series output mode, the input three-phase power can be complemented at the output side, so that the input side capacitor Cin and the output side capacitor Cout do not need to adopt large capacitance capacitors, only need to filter the high-frequency switching ripple, and do not need to filter the power frequency ripple. Thereby reducing the storage capacitance within the module.
Example two
A three-phase AC/DC power supply control system, referring to fig. 7, comprises a power electronic transformer formed by a plurality of three-phase AC/DC modules according to the first embodiment, wherein the input side of the power electronic transformer is connected to a medium-voltage alternating-current power supply network, the three-phase alternating-current phase of the medium-voltage alternating-current power supply network is obtained through a phase-locked loop, the phase distribution of the medium-voltage alternating-current voltage is carried out on each three-phase AC/DC module through a phase distributor, and a multi-level effect is generated on the medium-voltage three-phase alternating-current side by adopting a phase-shifting PWM mode among the three-phase AC/DC modules. The control system distributes a PWM phase reference theta i to each three-phase AC/DC module through the phase distributor, so that the PWM of each module keeps a fixed phase difference strictly, and therefore the elimination of switching ripples is facilitated.
The control of each three-phase AC/DC module is independent. The driving signals of the medium-voltage three-phase current-intersecting side of the three-phase AC/DC module are generated according to the phase, so as to drive the input side switch; the low voltage DC side of the three phase AC/DC module is power controlled to obtain a low voltage drive signal.
The operation principle of a three-phase AC/DC power electronic transformer is as follows. Suppose that the three-phase voltages on the medium-voltage three-phase current-intersecting side are as shown in fig. 8. The square waveform generated by the chopping of each module at time t1 is shown in fig. 9, and the duty ratio of each phase is proportional to the voltage amplitude, which can be determined by the three-phase ac phase, and the purpose of this is to ensure that the three-phase input current remains sinusoidal.
The low-voltage DC side adopts primary and secondary side phase shift control, and when the power flows from the high-voltage side to the low-voltage side, the phase of the PWM signal at the low-voltage side lags behind the phase of the PWM signal at the high-voltage side by a phase angle
Thereby controlling the phase shift angle
To achieve the magnitude of output powerAnd (5) controlling. Referring to fig. 10, since the output parallel connection mode is adopted, three-phase power is supplemented with each other, and a stable direct current voltage can be output.
Finally, it should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and those skilled in the art can make insubstantial changes and substitutions based on the present invention without departing from the protection scope of the present invention.
Claims (7)
1. The utility model provides a power electronic transformer of series-parallel hybrid connection which characterized in that: comprising a medium voltage three phase AC/DC side and a low voltage DC side connected by a plurality of three phase AC/DC modules, each three phase AC/DC module having 3 independent medium voltage AC ports and 1 low voltage DC port;
on the medium-voltage three-phase alternating current side, each phase of a three-phase AC/DC module serves as an AC/DC submodule, and 3 AC/DC submodules of each three-phase AC/DC module are respectively connected into a three-phase medium-voltage alternating current port through an inductor and are connected into a medium-voltage alternating current power supply network through each medium-voltage alternating current port through corresponding 1 medium-voltage alternating current port;
and on the low-voltage direct-current side, after each AC/DC sub-module of the three-phase AC/DC module is connected in series, each three-phase AC/DC module is connected in parallel, namely, the low-voltage direct-current side is formed by connecting all the low-voltage direct-current ports in parallel and is used for accessing a low-voltage direct-current output power grid.
2. A power electronic transformer according to claim 1, characterised in that:
each three-phase AC/DC module includes an input side H-bridge, each including an input side capacitor Cin, 4 input side switches Q1-Q4, and an input side inductor Lk, an electrical isolation element, and an output side H-bridge, each including 4 output side switches Q6-Q8, and an output side capacitor Cout.
3. A power electronic transformer according to claim 2, characterised in that:
the input side switches Q1-Q4 adopt bidirectional switches to realize bidirectional power flow; the output-side switches Q5-Q8 use insulated gate bipolar transistors IGBTs.
4. A power electronic transformer according to claim 2 or 3, characterised in that:
the electrical isolation element is a high-frequency transformer.
5. A three-phase AC/DC power supply control system, characterized by: the control system comprises a plurality of power electronic transformers according to any one of claims 1 to 4, wherein the input side of each power electronic transformer is connected to a medium-voltage alternating-current power supply network, the three-phase alternating-current phases of the medium-voltage alternating-current power supply network are obtained through a phase-locked loop, the phase distribution of medium-voltage alternating-current voltage is carried out on each three-phase AC/DC module through a phase distributor, and a multi-level effect is generated on the medium-voltage three-phase alternating-current side by adopting a phase-shifting PWM mode among the three-phase AC/DC modules.
6. The control system of claim 5, wherein: the driving signals of the medium-voltage three-phase current-intersecting side of the three-phase AC/DC module are generated according to the phase, so as to drive the input side switch; the low voltage DC side of the three phase AC/DC module is power controlled to obtain a low voltage drive signal.
7. The control system of claim 6, wherein: the low-voltage DC side adopts primary and secondary side phase shift control, when the power flows from the high-voltage side to the low-voltage side, the phase of the PWM signal at the low-voltage side lags behind the phase of the PWM signal at the high-voltage side by a phase angle
Thereby controlling the phase shift angle
And the control of the output power is realized.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110824335.5A CN113556051B (en) | 2021-07-21 | Power electronic transformer and control system for serial-parallel hybrid connection |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110824335.5A CN113556051B (en) | 2021-07-21 | Power electronic transformer and control system for serial-parallel hybrid connection |
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| Publication Number | Publication Date |
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| CN113556051A true CN113556051A (en) | 2021-10-26 |
| CN113556051B CN113556051B (en) | 2024-06-04 |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107181413A (en) * | 2017-07-15 | 2017-09-19 | 华北电力大学（保定） | Mixed type direct current power electronic transformer |
| CN107910872A (en) * | 2017-10-27 | 2018-04-13 | 东南大学 | A kind of dynamic electric voltage recovery device compound circuit and control method based on solid-state transformer |
| CN110798074A (en) * | 2019-11-11 | 2020-02-14 | 内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司 | Cascade type single-phase alternating current-to-direct current isolation converter |
| CN210327036U (en) * | 2019-05-29 | 2020-04-14 | 全球能源互联网研究院有限公司 | Alternating current-direct current power supply system with power supply end capable of being grounded |
| CN111682787A (en) * | 2020-05-18 | 2020-09-18 | 天津大学 | Single-stage three-phase AC/DC converter based on isolation converter module and method |
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107181413A (en) * | 2017-07-15 | 2017-09-19 | 华北电力大学（保定） | Mixed type direct current power electronic transformer |
| CN107910872A (en) * | 2017-10-27 | 2018-04-13 | 东南大学 | A kind of dynamic electric voltage recovery device compound circuit and control method based on solid-state transformer |
| CN210327036U (en) * | 2019-05-29 | 2020-04-14 | 全球能源互联网研究院有限公司 | Alternating current-direct current power supply system with power supply end capable of being grounded |
| CN110798074A (en) * | 2019-11-11 | 2020-02-14 | 内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司 | Cascade type single-phase alternating current-to-direct current isolation converter |
| CN111682787A (en) * | 2020-05-18 | 2020-09-18 | 天津大学 | Single-stage three-phase AC/DC converter based on isolation converter module and method |
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