CN111404409A - Multi-port power electronic transformer topology based on MMC and control method thereof - Google Patents
Multi-port power electronic transformer topology based on MMC and control method thereof Download PDFInfo
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- CN111404409A CN111404409A CN201910003922.0A CN201910003922A CN111404409A CN 111404409 A CN111404409 A CN 111404409A CN 201910003922 A CN201910003922 A CN 201910003922A CN 111404409 A CN111404409 A CN 111404409A
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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
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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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
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
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Abstract
The invention discloses a multi-port power electronic transformer topology based on MMC and a control method thereof, which can be used for electric energy conversion from medium-high voltage alternating current to medium-high voltage direct current and low-voltage direct current. On the basis of the MMC converter, the topology can output medium-high voltage direct current and low-voltage direct current simultaneously by increasing the full-bridge submodule and the high-frequency alternating current branch circuit formed by the inductance and the capacitance and matching with a corresponding control strategy, and has the advantages of small quantity of switching devices and passive devices, compact structure and high efficiency.
Description
Technical Field
The invention relates to a multi-port power electronic transformer topology based on MMC and a control method thereof, belonging to the technical field of power electronics.
Background
With the rapid development of renewable energy power generation and the increase of direct-current loads, the traditional power frequency transformer is not enough to meet the requirements and challenges of modern power systems due to the lack of an intelligent control link and a direct-current conversion port. And the power frequency transformer is huge in size and heavy, and requires a large floor area. With the rapid development of semiconductor devices, a novel intelligent transformer based on a high-power electronic converter technology is provided, the weight and the volume of the transformer can be reduced, various alternating current/direct current ports can be provided, the controllability is flexible and changeable, flexible access of various distributed energy sources, energy storage and loads is facilitated, and the possibility is provided for efficiently solving various problems faced by the current power grid.
At present, many researchers have proposed various power electronic transformer topologies, but generally, a modular multilevel converter or a cascaded full-bridge topology is used to rectify a high-voltage alternating current into a high-voltage direct current, and then a structure in which a plurality of DC-DC converters are connected in series and in parallel is used to step down the high-voltage direct current into a low-voltage direct current. The power electronic transformer topology has more electric energy conversion stages, uses more power devices, causes larger loss, has the circulating current problem in series-parallel connection of a plurality of direct current converters, and is required to be inhibited, and the control of the direct current conversion stages is complex. The cost is high, the control is complex, the reliability is low, the power density is low, and the large-scale use is difficult to realize.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a multi-port power electronic transformer topology based on an MMC and a control method thereof, which solve the problems that the power electronic transformer topology has more electric energy conversion stages, uses more power devices, causes higher loss and has the circulating current problem needing to be inhibited when a plurality of direct current converters are connected in series and in parallel.
The invention specifically adopts the following technical scheme to solve the technical problems:
multiport power electronic transformer topology based on MMC includes high-voltage AC level and low-voltage DC level two parts, wherein:
the high-voltage alternating-current stage is a three-phase six-bridge arm circuit, each phase of the three-phase six-bridge arm circuit comprises an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm are connected in series by a current-limiting reactor, M serially connected MMC half-bridge sub-modules and a high-frequency alternating-current branch; the high-frequency alternating current branch comprises N MMC full-bridge sub-modules, a resonant capacitor, a resonant inductor and a high-frequency transformer, wherein the N MMC full-bridge sub-modules are connected in series and then connected in parallel with a series branch consisting of the resonant capacitor, the resonant inductor and a primary side of the high-frequency transformer; one end of the upper bridge arm and one end of the lower bridge arm are connected with a high-voltage alternating-current power grid, and the other ends of the upper bridge arm and the lower bridge arm are respectively used as the positive electrode and the negative electrode of a high-voltage direct-current output port of the multi-port power electronic transformer topology.
The low-voltage direct-current stage comprises six full-bridge circuits, secondary sides of the high-frequency transformer in six bridge arms of the high-voltage alternating-current stage are respectively connected with the middle points of the full-bridge circuits, and positive electrodes and negative electrodes of the six full-bridge circuits of the low-voltage direct-current stage are respectively connected in parallel to form a low-voltage direct-current output port of the multi-port power electronic transformer topology.
The invention correspondingly provides the control method of the multi-port power electronic transformer topology based on the MMC, the modulation wave of the full-bridge submodule in the high-frequency alternating-current branch circuit is high-frequency alternating-current voltage, and the output voltage or current of the low-voltage direct-current stage is controlled by adjusting the amplitude of the high-frequency alternating-current voltage; the high-frequency alternating current voltage amplitude modulated by the high-frequency alternating current branch in each phase of upper and lower bridge arms is the same, but the phase difference is 180 degrees, so that no high-frequency alternating current component is connected in the high-voltage direct current port in series.
Furthermore, the high-frequency modulation wave adopted in the high-frequency alternating current branch circuit is a high-frequency square wave or a high-frequency alternating current waveform, and the frequency of the modulation wave is consistent with the resonant frequency of the resonant inductor and the resonant capacitor.
Furthermore, the half-bridge sub-module structure adopts a traditional half-bridge sub-module type MMC converter control strategy to regulate the output of a high-voltage alternating current side and a high-voltage direct current side;
the control strategies of the traditional half-bridge sub-module type MMC converter comprise control strategies of alternating current side control, sub-module voltage-sharing control, circulating current inhibition and the like; the alternating current side control strategy adopts voltage and current double closed loop control, voltage vector control and other strategies under a dq coordinate system; the sub-module voltage-sharing control strategy adopts a carrier phase-shifting control and a nearest level approximation strategy; the circulation suppression strategy adopts a double-frequency negative-sequence circulation suppression and quasi-proportional resonant circulation control strategy.
Further, for the low-voltage dc stage control, when energy flows into the low-voltage dc port, the full-bridge circuit adopts an uncontrolled rectification or synchronous rectification manner, and when energy flows from the low-voltage dc port to the high-voltage ac stage, the output voltage of the full-bridge circuit needs to be completely in phase with the modulation wave of the high-frequency ac branch. The resonant frequency of the high-frequency alternating-current branch circuit is consistent with the switching frequency of the low-voltage direct-current full-bridge circuit through parameter design, so that zero current switching of a switching tube of the low-voltage direct-current full-bridge circuit is realized.
By adopting the technical scheme, the invention can produce the following technical effects:
1. on the basis of the MMC converter, the power electronic transformer can simultaneously output medium-high voltage direct current and low-voltage direct current by adding the full-bridge submodule and the high-frequency alternating current branch circuit formed by the inductance and the capacitance and matching with a corresponding control strategy, and has the advantages of small quantity of switching devices and passive devices, compact structure and high efficiency.
2. The multi-port power electronic transformer topology based on the MMC and the control method thereof reduce the electric energy conversion from high-voltage direct current to low-voltage direct current in the original power electronic transformer, and only have two-stage structure from high-voltage alternating current to low-voltage direct current, thereby saving a large number of devices, being beneficial to improving the overall efficiency and reliability of the transformer and reducing the cost; and the power electronic transformer is also provided with a high-voltage direct-current port which can provide high-voltage direct-current voltage. In addition, zero current turn-off can be realized through the low-voltage direct-current stage H bridge, the current stress of a low-voltage direct-current stage switching device is reduced, and the transmission efficiency is improved.
Drawings
Fig. 1 is a circuit topology diagram of a multi-port power electronic transformer based on MMC according to the present invention.
Detailed Description
The following describes embodiments of the present invention with reference to the drawings.
As shown in fig. 1, the present invention provides a multi-port power electronic transformer topology based on MMC, which includes two parts, namely a high-voltage ac stage and a low-voltage dc stage, wherein:
the high-voltage alternating-current stage is a three-phase six-bridge arm circuit, each phase of the three-phase six-bridge arm circuit comprises an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm are connected in series by a current-limiting reactor, M serially connected MMC half-bridge sub-modules and a high-frequency alternating-current branch; the high-frequency alternating current branch comprises N MMC full-bridge sub-modules, a resonant capacitor, a resonant inductor and a high-frequency transformer, wherein the N MMC full-bridge sub-modules are connected in series and then connected in parallel with a series branch consisting of the resonant capacitor, the resonant inductor and a primary side of the high-frequency transformer; one end of the upper bridge arm and one end of the lower bridge arm are connected with a high-voltage alternating-current power grid, and the other ends of the upper bridge arm and the lower bridge arm are respectively used as the positive electrode and the negative electrode of a high-voltage direct-current output port of the multi-port power electronic transformer topology.
The low-voltage direct-current stage comprises six full-bridge circuits, secondary sides of the high-frequency transformer in six bridge arms of the high-voltage alternating-current stage are respectively connected with the middle points of the full-bridge circuits, and positive electrodes and negative electrodes of the six full-bridge circuits of the low-voltage direct-current stage are respectively connected in parallel to form a low-voltage direct-current output port of the multi-port power electronic transformer topology.
The control method of the multi-port power electronic transformer topology based on the MMC in the embodiment comprises the following steps that the modulation wave of the full-bridge submodule in the high-frequency alternating-current branch circuit is high-frequency alternating-current voltage, and the output voltage or current of the low-voltage direct-current stage is controlled by adjusting the amplitude of the high-frequency alternating-current voltage; the high-frequency alternating current voltage amplitude modulated by the high-frequency alternating current branch in each phase of upper and lower bridge arms is the same, but the phase difference is 180 degrees, so that no high-frequency alternating current component is connected in the high-voltage direct current port in series.
The high-frequency modulation wave adopted in the high-frequency alternating current branch circuit is a high-frequency square wave or a high-frequency alternating current waveform, and the frequency of the modulation wave is consistent with the resonant frequency of the resonant inductor and the resonant capacitor.
The half-bridge submodule structure adopts a traditional half-bridge submodule type MMC converter control strategy to regulate the output of a high-voltage alternating current side and a high-voltage direct current side;
the control strategies of the traditional half-bridge sub-module type MMC converter comprise control strategies of alternating current side control, sub-module voltage-sharing control, circulating current inhibition and the like; the alternating current side control strategy adopts voltage and current double closed loop control, voltage vector control and other strategies under a dq coordinate system; the sub-module voltage-sharing control strategy adopts a carrier phase-shifting control and a nearest level approximation strategy; the circulation suppression strategy adopts a double-frequency negative-sequence circulation suppression and quasi-proportional resonant circulation control strategy.
For the low-voltage direct-current stage control, when energy flows into the low-voltage direct-current port, the full-bridge circuit adopts an uncontrolled rectification or synchronous rectification mode, and when the energy flows from the low-voltage direct-current port to the high-voltage alternating-current stage, the output voltage of the full-bridge circuit needs to be completely in phase with the modulation wave of the high-frequency alternating-current branch circuit. The zero current switch of the low-voltage direct-current full-bridge circuit switching tube can be realized by reasonably designing the resonance parameters of the high-frequency alternating-current branch.
The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.
Claims (6)
1. Multiport power electronic transformer topology based on MMC, its characterized in that: the multi-port power electronic transformer topology comprises a high-voltage alternating-current stage and a low-voltage direct-current stage, wherein:
the high-voltage alternating-current stage is a three-phase six-bridge arm circuit, each phase of the three-phase six-bridge arm circuit comprises an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm are connected in series by a current-limiting reactor, M serially connected MMC half-bridge sub-modules and a high-frequency alternating-current branch; the high-frequency alternating current branch comprises N MMC full-bridge sub-modules, a resonant capacitor, a resonant inductor and a high-frequency transformer, wherein the N MMC full-bridge sub-modules are connected in series and then connected in parallel with a series branch consisting of the resonant capacitor, the resonant inductor and a primary side of the high-frequency transformer; one end of the upper bridge arm and one end of the lower bridge arm are connected with a high-voltage alternating-current power grid, and the other ends of the upper bridge arm and the lower bridge arm are respectively used as the positive pole and the negative pole of a high-voltage direct-current output port of the multi-port power electronic transformer topology;
the low-voltage direct-current stage comprises six full-bridge circuits, secondary sides of the high-frequency transformer in six bridge arms of the high-voltage alternating-current stage are respectively connected with the middle points of the full-bridge circuits, and positive electrodes and negative electrodes of the six full-bridge circuits of the low-voltage direct-current stage are respectively connected in parallel to form a low-voltage direct-current output port of the multi-port power electronic transformer topology.
2. The method of controlling an MMC-based multi-port power electronic transformer topology of claim 1, wherein: the modulation wave of the full-bridge submodule in the high-frequency alternating current branch circuit is high-frequency alternating current voltage, and the output voltage or current of the low-voltage direct current stage is controlled by adjusting the amplitude of the high-frequency alternating current voltage; the high-frequency alternating current voltage amplitude modulated by the high-frequency alternating current branch in each phase of upper and lower bridge arms is the same, but the phase difference is 180 degrees, so that no high-frequency alternating current component is connected in the high-voltage direct current port in series.
3. The method of controlling an MMC-based multi-port power electronic transformer topology as claimed in claim 2, characterized by: the high-frequency modulation wave adopted in the high-frequency alternating current branch circuit is a high-frequency square wave or a high-frequency alternating current waveform, and the frequency of the modulation wave is consistent with the resonant frequency of the resonant inductor and the resonant capacitor.
4. The method of controlling an MMC-based multi-port power electronic transformer topology as claimed in claim 2, characterized by: the half-bridge submodule structure adopts a traditional half-bridge submodule type MMC converter control strategy to regulate the output of a high-voltage alternating current side and a high-voltage direct current side;
the control strategies of the traditional half-bridge sub-module type MMC converter comprise control strategies of alternating current side control, sub-module voltage-sharing control, circulating current inhibition and the like; the alternating current side control strategy adopts voltage and current double closed loop control, voltage vector control and other strategies under a dq coordinate system; the sub-module voltage-sharing control strategy adopts a carrier phase-shifting control and a nearest level approximation strategy; the circulation suppression strategy adopts a double-frequency negative-sequence circulation suppression and quasi-proportional resonant circulation control strategy.
5. The method of controlling an MMC-based multi-port power electronic transformer topology as claimed in claim 2, characterized by: for the low-voltage DC stage control, when energy flows into the low-voltage DC port, the full-bridge circuit adopts an uncontrolled rectification or synchronous rectification mode, and when the energy flows from the low-voltage DC port to the high-voltage AC stage, the output voltage of the full-bridge circuit needs to be completely in phase with the modulation wave of the high-frequency AC branch circuit.
6. The method of controlling an MMC-based multi-port power electronic transformer topology of claim 5, wherein: the resonant frequency of the high-frequency alternating-current branch circuit is consistent with the switching frequency of the low-voltage direct-current full-bridge circuit through parameter design, so that zero current switching of a switching tube of the low-voltage direct-current full-bridge circuit is realized.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111817599A (en) * | 2020-07-16 | 2020-10-23 | 哈尔滨工业大学 | Multi-port electric energy router and control method thereof |
| CN113054861A (en) * | 2021-03-08 | 2021-06-29 | 东南大学 | Series MMC converter topological structure with few modules |
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| EP2568589A1 (en) * | 2011-09-08 | 2013-03-13 | ABB Technology AG | Multilevel converter comprising an active AC-DC converter and a resonant DC-DC converter and a control method for operating a multilevel converter |
| CN106533189A (en) * | 2016-11-25 | 2017-03-22 | 中国科学院电工研究所 | Power electronic transformer and control method thereof |
| CN106787861A (en) * | 2017-01-16 | 2017-05-31 | 华北电力大学 | Modular multilevel full-bridge mode of resonance electric power electric transformer topology |
| CN107134930A (en) * | 2017-06-30 | 2017-09-05 | 西安科技大学 | Power electronics distribution transformer and its control method based on MMC |
| CN107623456A (en) * | 2017-09-29 | 2018-01-23 | 东南大学 | Multiport electric power electric transformer topology and its control method based on MMC |
-
2019
- 2019-01-03 CN CN201910003922.0A patent/CN111404409A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2568589A1 (en) * | 2011-09-08 | 2013-03-13 | ABB Technology AG | Multilevel converter comprising an active AC-DC converter and a resonant DC-DC converter and a control method for operating a multilevel converter |
| CN106533189A (en) * | 2016-11-25 | 2017-03-22 | 中国科学院电工研究所 | Power electronic transformer and control method thereof |
| CN106787861A (en) * | 2017-01-16 | 2017-05-31 | 华北电力大学 | Modular multilevel full-bridge mode of resonance electric power electric transformer topology |
| CN107134930A (en) * | 2017-06-30 | 2017-09-05 | 西安科技大学 | Power electronics distribution transformer and its control method based on MMC |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111817599A (en) * | 2020-07-16 | 2020-10-23 | 哈尔滨工业大学 | Multi-port electric energy router and control method thereof |
| CN113054861A (en) * | 2021-03-08 | 2021-06-29 | 东南大学 | Series MMC converter topological structure with few modules |
| CN113054861B (en) * | 2021-03-08 | 2022-03-29 | 东南大学 | Series MMC converter topological structure with few modules |
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