CN106100361A - A kind of ac-dc conversion circuit and electric power electric transformer - Google Patents

Abstract

The present invention provides an AC-DC conversion circuit. The three-phase instantaneous power is coupled and added through the coupling unit, which effectively offsets the fluctuations of the fundamental frequency and the double frequency on the bridge arms of each phase. A large-capacity capacitor is installed on each commutation sub-unit, which greatly reduces the volume of the AC-DC conversion circuit. If the AC-DC conversion circuit is applied to a power electronic transformer, it can also effectively reduce the volume of the power electronic transformer and reduce its cost. .

Description

An AC-DC conversion circuit and power electronic transformer

technical field

The invention relates to the technical field of power equipment, in particular to an AC-DC conversion circuit and a power electronic transformer.

Background technique

Power electronic transformer, also known as solid-state transformer, is a new type of power distribution transformer device that has attracted people's attention with the development of power electronics technology in recent years. It adopts the latest power electronic conversion technology to convert power frequency alternating current into high frequency alternating current or direct current, then isolates it with high frequency transformer to realize the transformation of voltage and current, and finally converts high frequency alternating current into power frequency alternating current or direct current Inverted to power frequency alternating current for use by power grid users. In addition to the functions of conventional transformers such as voltage transformation, isolation, and energy transfer, power electronic transformers also have functions such as reactive power compensation, harmonic control, grid interconnection, and new energy grid connection. They are expected to be widely used in future grids.

In the prior art, the three phases of a traditional multilevel topology power electronic transformer include an upper bridge arm and a lower bridge arm, and each bridge arm contains a plurality of cascaded sub-modules, and each sub-module may include an H-bridge or a half-bridge. Bridge rectifier circuit. Single-phase voltage control is performed by controlling the number of input sub-modules of the upper and lower bridge arms. Because there are power fluctuations in single-phase, in order to reduce the voltage fluctuation caused by single-phase fluctuating power, it is usually necessary to install a DC capacitor on each sub-module to suppress the voltage fluctuation caused by single-phase fluctuating power, but the DC voltage fluctuation caused by single-phase fluctuating power Larger, can only increase the single-phase capacitor capacity to effectively suppress single-phase fluctuating power, and the increase in capacity will lead to an increase in the volume and cost of the DC capacitor, which in turn leads to a large footprint of the entire power electronic transformer and a high cost. high.

Contents of the invention

The technical problem to be solved by the embodiment of the present invention is that the power electronic transformer in the prior art occupies a large area and is expensive.

For this reason, the embodiment of the present invention provides following technical scheme:

An embodiment of the present invention provides an AC-DC conversion circuit, including at least one set of AC-DC conversion modules, each set of AC-DC conversion modules includes at least one conversion branch, and each conversion branch includes:

Multiple commutation sub-units, respectively corresponding to three-phase alternating current;

A plurality of first DC/AC conversion units are respectively connected to the DC side of the converter sub-unit or the total DC side formed by connecting the DC side of the converter sub-unit in series or in parallel;

a coupling unit, coupling and summing the instantaneous power output by the first DC/AC conversion unit in each phase to eliminate fluctuations in the instantaneous power in a single phase;

At least one AC/DC conversion unit connected to one or more output terminals of the coupling unit;

In addition, the adjacent converter sub-units of the same phase in the AC-DC conversion module are connected in cascade, and the AC interface is led out from the AC side of the converter sub-unit in each phase, and is connected to the AC power of the corresponding phase.

In the AC/DC conversion circuit described in the embodiment of the present invention, the output ends of the AC/DC conversion units in each of the conversion branches are connected in series or in parallel, and the output ends of the AC/DC conversion units connected in series or in parallel As an isolated conversion DC interface.

In the AC/DC conversion circuit according to the embodiment of the present invention, the coupling unit includes at least one transformer, the primary side of the transformer includes a plurality of primary windings, and the output of the first DC/AC conversion unit corresponding to the Terminal or the total output terminal of multiple first DC/AC conversion units connected in series or in parallel, the secondary side includes at least one secondary winding, the output terminal of each secondary winding or a plurality of secondary windings The output terminals connected in series or in parallel are used as the output terminals of the coupling unit and connected to the input terminals of the AC/DC conversion unit.

In the AC/DC conversion circuit according to the embodiment of the present invention, the commutation subunit includes at least one first commutation subcircuit, and the first commutation subcircuit includes a first switching device, a second switching device, a first two pole tube and a second diode;

The first switching device and the second switching device are connected in series, the first diode and the second diode are respectively connected in antiparallel to the first switching device and the second switching device, and the The common terminal of the first switching device and the second switching device and the anode of the second diode serve as the AC side of the commutation sub-unit, and the cathode of the first diode and the second two The anode of the pole tube is used as the DC side of the commutation sub-unit.

In the AC/DC conversion circuit according to the embodiment of the present invention, the commutation subunit includes at least one second commutation subcircuit, and the second commutation subcircuit includes a first switching device, a second switching device, a third switch device, a fourth switching device, a first diode, a second diode, a third diode, and a fourth diode;

The series branch of the first switching device and the third switching device is connected in parallel with the series branch of the second switching device and the fourth switching device, the first diode, the second The diode, the third diode and the fourth diode are connected in antiparallel with the first switching device, the second switching device, the third switching device and the fourth switching device respectively , the common end of the first switching device and the third switching device and the common end of the second switching device and the fourth switching device serve as the AC side of the commutation subunit, and the two series The common end of the branches connected in parallel serves as the DC side of the converter sub-units.

In the AC/DC conversion circuit according to the embodiment of the present invention, the commutation subunit includes at least one third commutation subcircuit, and the third commutation subcircuit includes a first switching device, a second switching device, a third switch a device, a first diode, a second diode, a third diode, and a fourth diode;

The first switching device and the second switching device are connected in series, and the first diode and the second diode are respectively connected in antiparallel to the first switching device and the second switching device, so The third diode and the third switching device are connected in antiparallel, and the anode of the third diode is connected to the anode of the second diode at the same time, and the cathode of the third diode is connected to the anode of the second diode at the same time The anode of the fourth diode is connected, the cathode of the fourth diode is connected to the cathode of the first diode, and the common terminal of the first switching device and the second switching device is connected to the The collector of the third switching device serves as the AC side of the commutation subunit, and the cathode of the first diode and the anode of the third diode serve as the DC side of the commutation subunit.

In the AC/DC conversion circuit according to the embodiment of the present invention, the commutation subunit includes at least one fourth commutation subcircuit, and the fourth commutation subcircuit includes a first switching device, a second switching device, a third switch device, a fourth switching device, a fifth switching device, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode and a seventh diode;

The first switching device and the third switching device are connected in series, and the first diode and the third diode are respectively connected in antiparallel to the first switching device and the third switching device; The second switching device and the fourth switching device are connected in series, and the second diode and the fourth diode are respectively connected in antiparallel to the second switching device and the fourth switching device; The emitter of the fifth switching device is connected to the anode of the third diode, the collector of the fifth switching device is connected to the cathode of the second diode, and the fifth diode is connected to the anode of the second diode. The fifth switching device is connected in antiparallel; the anode of the sixth diode is connected to the cathode of the fifth diode, and the cathode of the sixth diode is connected to the cathode of the first diode, so The anode of the seventh diode is connected to the anode of the fourth diode, the cathode of the seventh diode is connected to the anode of the third diode, and the first switching device and the The common end of the third switching device and the common end of the second switching device and the fourth switching device serve as the AC side of the commutation sub-unit, and the cathode of the first diode and the third and second The anode of the pole tube serves as one DC side of the commutation subunit, and the cathode of the second diode and the anode of the fourth diode serve as the other DC side of the commutation subunit.

In the AC/DC conversion circuit according to the embodiment of the present invention, the commutation subunit includes at least one combined commutation subcircuit;

The combined commutation sub-circuit is composed of any two or more of the first commutation sub-circuit, the second commutation sub-circuit, the third commutation sub-circuit and the fourth commutation sub-circuit composition.

The AC/DC conversion circuit according to the embodiment of the present invention further includes at least one DC capacitor connected to the output end of the AC/DC conversion unit, or the output end of the AC/DC conversion unit connected in series or in parallel, and The output end of the DC capacitor is used as an isolation conversion DC interface.

In the AC-DC conversion circuit described in the embodiment of the present invention, the total positive poles of the cascaded-connected converter subunits of each phase are connected together as the positive pole of the DC interface, and the total positive poles of the cascaded-connected converter subunits of each phase are The negative poles are connected together as the negative pole of the DC interface.

The AC-DC conversion circuit described in the embodiment of the present invention further includes a second DC/AC conversion unit connected to the isolated conversion DC interface, and the output end of the second DC/AC conversion unit is used as the isolation conversion AC interface .

An embodiment of the present invention also provides a power electronic transformer, including the above-mentioned AC-DC conversion circuit.

The technical scheme of the embodiment of the present invention has the following advantages:

The embodiment of the present invention provides an AC-DC conversion circuit, which couples and sums the three-phase instantaneous power through the coupling unit, effectively cancels the fundamental frequency and double frequency fluctuations on the bridge arms of each phase, and does not need to suppress single-phase fluctuation power Installing a large-capacity capacitor on each commutation subunit greatly reduces the volume of the AC-DC conversion circuit. If the AC-DC conversion circuit is applied to a power electronic transformer, it can also effectively reduce the volume of the power electronic transformer and reduce the its cost.

Description of drawings

In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the description of the specific embodiments or prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a structural block diagram of a specific example of an AC-DC conversion circuit in Embodiment 1 of the present invention;

Fig. 2 is the circuit schematic diagram of a specific example of the transformer in the AC-DC conversion circuit of Embodiment 1 of the present invention;

FIG. 3 is a schematic circuit diagram of a specific example of the first commutation sub-circuit in the AC-DC conversion circuit in Embodiment 1 of the present invention;

Fig. 4 is a schematic circuit diagram of a specific example of the second commutation sub-circuit in the AC-DC conversion circuit in Embodiment 1 of the present invention;

Fig. 5 is a schematic circuit diagram of a specific example of the third commutation sub-circuit in the AC-DC conversion circuit in Embodiment 1 of the present invention;

FIG. 6 is a schematic circuit diagram of a specific example of the fourth commutation sub-circuit in the AC-DC conversion circuit in Embodiment 1 of the present invention;

FIG. 7 is a structural block diagram of another specific example of the AC-DC conversion circuit in Embodiment 1 of the present invention.

Reference signs:

1-AC-DC conversion module; 11-commutation sub-unit; 12-first DC/AC conversion unit; 13-coupling unit; 14-AC/DC conversion unit.

detailed description

The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Apparently, the described embodiments are part of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In the description of the embodiments of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer " and other indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, Constructed and operative in a particular orientation and therefore are not to be construed as limitations of the invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and should not be construed as indicating or implying relative importance.

In the description of the embodiments of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a A detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediary; it may also be an internal connection between two components, it may be a wireless connection, or is a wired connection. Those of ordinary skill in the art can understand the specific meanings of the above terms in the embodiments of the present invention in specific situations.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as there is no conflict with each other.

Example 1

This embodiment provides an AC-DC conversion circuit, as shown in FIG. 1 , including at least one set of AC-DC conversion modules 1, each group of AC-DC conversion modules 1 includes at least one conversion branch, and each conversion branch includes:

A plurality of commutation sub-units 11 respectively correspond to three-phase alternating current. Specifically, the commutation subunit 11 can effectively convert and control electric energy, for example, the AC power can be rectified and AC voltage regulated by controlling the switching state and switching frequency of the switching devices in the commutation subunit 11 . If the structures of the commutation subunits 11 in each conversion branch are exactly the same, the number of commutation subunits 11 put into use in each phase of each conversion branch is consistent, so that the commutation subunits in each phase 11 have the same total output power; of course, if the structures of the commutation subunits 11 in each conversion branch are inconsistent, it is necessary to ensure that the total output power of the commutation subunits 11 put into use in each phase is consistent.

A plurality of first DC/AC conversion units 12 are respectively connected to the DC side of the commutation sub-unit 11 or the total DC side formed by connecting the DC side of the commutation sub-unit 11 in series or in parallel. Specifically, the connection relationship between the first DC/AC conversion unit 12 and the DC side of the commutation sub-unit 11 can be determined according to specific requirements. For example, if it is necessary to reduce the number of switching devices in the AC-DC conversion circuit, the first DC/AC conversion unit can be 12 is connected to the total DC side formed by connecting the DC side of the commutation subunit 11 in each phase of the conversion branch in series to increase the amplitude of the voltage output by the first DC/AC conversion unit 12 and reduce the first DC/AC conversion The number of units, thereby reducing the number of switching devices; of course, if the current in the switching device needs to be reduced, the first DC/AC conversion unit 12 can be connected in parallel with the DC side of the commutation sub-unit 11 in each phase of the conversion branch. The total DC side is connected. For example, when each phase of the conversion branch circuit includes two commutation subunits 11 of the same structure, in order to reduce the number of switching devices, the DC side of the two commutation subunits 11 in each phase can be connected in series, and the commutation subunits 11 formed after series connection The total DC side is connected to the input end of the first DC/AC conversion unit 12, which can reduce the number of the first DC/AC conversion unit 12 by half. Of course, if the withstand voltage of the switching device is not high enough, the first DC/AC conversion unit cannot be reduced. The number of AC conversion units 12, the DC side of each commutation subunit 11 can be connected to the input end of a first DC/AC conversion unit 12, or the first DC/AC conversion unit 12 can be connected to each conversion branch The total DC side formed by the parallel connection of the DC sides of the commutation subunits 11 in the phase is connected to reduce the voltage borne by each switching device; if each commutation subunit 11 has two DC side ports, each The DC side ports are regarded as the DC side of the commutation subunit 11, and are respectively connected to the input end of a first DC/AC conversion unit 12, or the DC side ports of the commutation subunit 11 can be connected in series as the commutation unit 11. The DC side of the subunit 11 can only be connected to the input end of a first DC/AC conversion unit 12; the first DC/AC conversion unit 12 can use any DC/AC conversion circuit in the prior art to convert each The direct current output from the direct current side of the commutation sub-unit 11 is converted into a square wave voltage, preferably a DC/AC conversion circuit capable of converting into a medium and high frequency square wave voltage. The DC side of the commutation sub-unit 11 is converted into a medium-high frequency square wave voltage by a DC/AC conversion circuit and then isolated and coupled.

The coupling unit 13 couples and sums the instantaneous power output by the first DC/AC conversion unit 12 in each phase to eliminate fluctuations in instantaneous power in a single phase. Specifically, the coupling unit 13 may include a plurality of input terminals and at least one output terminal, and each input terminal may be connected to the output terminal of a first DC/AC conversion unit 12 as required, or connected to multiple first DC/AC conversion units in the same phase. The total output terminals of the DC/AC conversion units 12 connected in series or in parallel are connected and the like.

At least one AC/DC conversion unit 14 is connected to one or more output ends of the coupling unit 13 . Specifically, the AC/DC conversion unit 14 may select any AC/DC conversion circuit in the prior art to convert the voltage after three-phase coupling by the coupling unit 13 into direct current.

In addition, the adjacent commutation subunits 11 of the same phase in the AC/DC conversion module 1 are connected in cascade, and the AC interface is led out from the AC side of the commutation subunit 11 in each phase, and connected to the corresponding phase's AC power. Specifically, the AC side of a certain commutation subunit 11 is connected in series with the AC side of an adjacent commutation subunit 11, and so on, forming a cascade connection of adjacent commutation subunits of the same phase, if An AC-DC conversion circuit includes multiple sets of AC-DC conversion modules 1, and the AC sides of the commutation sub-units 11 of the same phase in all AC-DC conversion modules 1 are connected in series, which also constitutes a space between adjacent commutation sub-units 11. cascade connection.

Specifically, FIG. 1 shows an AC-DC conversion circuit including two sets of AC-DC conversion modules 1 . The AC interface is drawn from the common end of the two sets of AC-DC conversion modules 1 and connected to the corresponding phase AC. In this way, the three phases a, b, and c have upper and lower bridge arms respectively, which belong to different groups of AC-DC conversion modules 1. One or more controllers can be used to control the input of the upper and lower bridge arms. The bridge arm voltage is controlled by commutating the number of sub-units 11 . Preferably, each bridge arm contains the same number of commutation subunits 11, which is more conducive to the control of switching on and off of the commutation subunits 11 on the bridge arm. Common modulation methods include nearest level approximation, carrier stacking, and equal carrier shifting. Taking phase a as an example, the current flowing through the upper bridge arm of phase a and the voltage across the upper bridge arm are

In the formula, U _dc is the DC voltage, I _dc is the DC current, U _ac is the peak value of the phase voltage of phase a, and I _ac is the peak value of the AC side line current of phase a.

The instantaneous power flowing through the upper bridge arm of phase a is calculated by the following formula:

It can be seen that the instantaneous power of the upper bridge arm of phase a includes a DC component, a fundamental frequency fluctuation component and a double frequency fluctuation component.

Calculate the output power of the high-frequency square wave voltage of the three phases a, b, and c in each conversion branch after being coupled by the coupling unit 13 by the following formula:

Because the three phases of alternating current operate symmetrically, and the phases a, b, and c have a phase difference of 120°, when the three-phase instantaneous power is coupled and added through the coupling unit 13, the fluctuations of the fundamental frequency and the double frequency are offset, ensuring the output power of the coupling unit 13 Basically no fluctuations. It is no longer necessary to install large-capacity capacitors on each commutation subunit 11 in order to suppress the fluctuation of single-phase instantaneous power, which greatly reduces the volume of the AC-DC conversion circuit, and the AC-DC conversion circuit in this embodiment is applied to power electronics Power equipment such as transformers can also effectively reduce the size and cost of power electronic transformers.

Preferably, in the AC/DC conversion circuit in this embodiment, the output ends of the AC/DC conversion units 14 in each conversion branch are connected in series or in parallel, and the output ends of the AC/DC conversion units 14 connected in series or in parallel are used as Isolated conversion DC interface. Specifically, connecting the output terminals of the AC/DC conversion units 14 in each conversion branch in parallel can further reduce the fluctuation of the DC voltage output by the isolated conversion DC interface, and can obtain from one or more AC/DC conversion units connected in parallel as required. The output terminal of the DC conversion unit 14 leads to the isolated conversion DC interface; connecting the output terminals of the AC/DC conversion units 14 in each conversion branch in series can increase the amplitude of the voltage output by the isolated conversion DC interface.

Preferably, in the AC-DC conversion circuit in this embodiment, the coupling unit 13 includes at least one transformer, and the primary side of the transformer includes a plurality of primary windings, respectively corresponding to the output terminals of the first DC/AC conversion unit 12 or multiple The first DC/AC conversion unit 12 is connected in series or in parallel to the total output end, and the secondary side includes at least one secondary winding, and the output end of each secondary winding or the output of multiple secondary windings in series or in parallel As the output terminal of the coupling unit 13, the terminal is connected to the input terminal of the AC/DC conversion unit 14. Specifically, according to requirements, the output terminal of multiple secondary windings in series can be used as the output terminal of coupling unit 13, which can increase the amplitude of the output voltage of coupling unit 13; the output terminal after multiple secondary windings can also be connected in parallel As the output terminal of the coupling unit 13, the voltage fluctuation at the output terminal of the coupling unit 13 and the current value in each secondary winding can be further reduced. As shown in Figure 2, it is a medium-high frequency transformer with three inputs and one output. By adjusting the number of turns of the primary and secondary windings put into use to adjust the transformation ratio of the transformer, the required low-voltage DC voltage value can be obtained. The high-frequency square wave voltage output by the first DC/AC conversion unit 12 of each phase in the conversion branch is isolated and coupled by the medium-high frequency transformer, the double frequency power on the AC side is automatically balanced between phases, and the power fluctuation of each phase can also be automatically balanced. There is no need to install large-capacity capacitors on each commutation sub-unit 11, which greatly reduces the volume and cost of the entire AC-DC conversion circuit, and at the same time reduces the difficulty of controlling the voltage equalization of the bridge arms.

Preferably, as shown in FIG. 3 , the commutation subunit 11 includes at least one first commutation subcircuit, and the first commutation subcircuit includes a first switching device T1, a second switching device T2, a first diode D1 and the second diode D2.

The first switching device T1 and the second switching device T2 are connected in series, the first diode D1 and the second diode D2 are connected in antiparallel with the first switching device T1 and the second switching device T2 respectively, and the first switching device T1 and the second The common terminal of the switching device T2 and the anode of the second diode D2 serve as the AC side of the commutation subunit 11, and the cathode of the first diode D1 and the anode of the second diode D2 serve as the DC side of the commutation subunit 11. side. Specifically, the commutation subunit 11 with the above structure, under the control of the controller, when the first switching device T1 is turned on and the second switching device T2 is turned off, the commutation subunit 11 is put into operation, and the commutation subunit 11 is equivalent to When the first switching device T1 is turned off and the second switching device T2 is turned on, the commutation subunit 11 is out of operation, and the commutation subunit 11 is equivalent to a short circuit to the outside, which is equivalent to directly bypassing the The commutation subunit 11 is taken out of operation. Therefore, the voltage of the upper and lower bridge arms can be controlled by controlling the number of commutation subunits 11 put into operation at the upper and lower bridge arms.

Preferably, as shown in FIG. 4 , another commutation subunit 11 structure is provided, including at least one second commutation subcircuit, and the second commutation subcircuit includes a first switching device T1, a second switching device T2 , a third switching device T3, a fourth switching device T4, a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4.

The series branch of the first switching device T1 and the third switching device T3 is connected in parallel with the series branch of the second switching device T2 and the fourth switching device T4, the first diode D1, the second diode D2, the third The diode D3 and the fourth diode D4 are respectively connected in antiparallel with the first switching device T1, the second switching device T2, the third switching device T3 and the fourth switching device T4, and the first switching device T1 and the third switching device T3 The common terminal of the second switching device T2 and the common terminal of the fourth switching device T4 serve as the AC side of the commutation subunit 11, and the common terminal after the two series branches are connected in parallel serves as the DC side of the commutation subunit 11. Specifically, if the circuit of the commutation subunit 11 with the above structure operates normally without failure, under the control of the controller, when the first switching device T1 and the fourth switching device T4 are turned on, the commutation subunit 11 is put into operation, The first terminal and the second terminal of the commutation subunit 11 are equivalent to a DC source; when the first switching device T1 and the second switching device T2 are turned on, or the third switching device T3 and the fourth switching device T4 are turned on When , the commutation sub-unit 11 is out of operation, and the voltage between the first terminal and the second terminal outputs 0 voltage. Through the above structural setting, when the commutation subunit 11 is out of operation, the controller can control the first switching device T1, the second switching device T2, the third switching device T3 and the fourth switching device T4 of the commutating subunit 11 Alternate turn-on to even out the switching loss; if the circuit fails, the first switching device T1, the second switching device T2, the third switching device T3 and the fourth switching device T4 are blocked (turned off) under the control of the controller, and the switching device T4 can be cut off. Short circuit current, isolated fault.

Preferably, as shown in FIG. 5 , a third commutation subunit 11 structure is provided, including at least one third commutation subcircuit, and the third commutation subcircuit includes a first switching device T1, a second switching device T2 , the third switching device T3, the first diode D1, the second diode D2, the third diode D3 and the fourth diode D4.

The first switching device T1 and the second switching device T2 are connected in series, the first diode D1 and the second diode D2 are connected in antiparallel to the first switching device T1 and the second switching device T2 respectively, and the third diode D3 and The third switching device T3 is connected in antiparallel, and the anode of the third diode D3 is connected to the anode of the second diode D2 at the same time, and the cathode of the third diode D3 is connected to the anode of the fourth diode D4 at the same time, and the anode of the third diode D3 is connected to the anode of the fourth diode D4 at the same time. The cathode of the four diodes D4 is connected to the cathode of the first diode D1, the common terminal of the first switching device T1 and the second switching device T2 and the collector of the third switching device T3 serve as the AC side of the commutation sub-unit 11 , the cathode of the first diode D1 and the anode of the third diode D3 serve as the DC side of the commutation sub-unit 11 . Specifically, in the commutation sub-unit 11 with the above structure, if the circuit operates normally without failure, under the control of the controller, the third switching device T3 is always turned on, and if the first switching device T1 is turned on, the second switching device T2 is turned off. If the first switching device T1 is turned off, the second switching device T2 is turned on, and the commutating subunit 11 is out of operation; if the circuit breaks down, it will be locked (closed) under the control of the controller. off) the first switching device T1, the second switching device T2 and the third switching device T3 can cut off the short-circuit current and isolate the fault.

Preferably, as shown in FIG. 6 , a fourth commutation subunit 11 structure is provided, including at least one fourth commutation subcircuit, and the fourth commutation subcircuit includes a first switching device T1, a second switching device T2 , the third switching device T3, the fourth switching device T4, the fifth switching device T5, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth and second Diode D5, sixth diode D6 and seventh diode D7.

The first switching device T1 and the third switching device T3 are connected in series, and the first diode D1 and the third diode D3 are connected in antiparallel with the first switching device T1 and the third switching device T3 respectively; the second switching device T2 and the third switching device T3 The four switching devices T4 are connected in series, and the second diode D2 and the fourth diode D4 are connected in antiparallel with the second switching device T2 and the fourth switching device T4 respectively; the emitter of the fifth switching device T5 is connected to the third diode The anode of D3 is connected, the collector of the fifth switching device T5 is connected to the cathode of the second diode D2, and the fifth diode D5 is connected in antiparallel with the fifth switching device T5; the anode of the sixth diode D6 is connected to the fifth The cathode of the diode D5 is connected, the cathode of the sixth diode D6 is connected to the cathode of the first diode D1, the anode of the seventh diode D7 is connected to the anode of the fourth diode D4, and the seventh diode The cathode of the tube D7 is connected to the anode of the third diode D3, and the common terminal of the first switching device T1 and the third switching device T3 and the common terminal of the second switching device T2 and the fourth switching device T4 serve as the commutation sub-unit 11 The cathode of the first diode D1 and the anode of the third diode D3 serve as a DC side of the commutation subunit 11, and the cathode of the second diode D2 and the anode of the fourth diode D4 serve as The other DC side of the commutation subunit 11.

Table 1

Specifically, as shown in Table 1, the commutation subunit 11 with the above structure works normally. In the first case, under the control of the controller, the first switching device T1 is turned on, the second switching device T2 is turned off, and the third switch The device T3 is turned off, the fourth switching device T4 is turned on, the fifth switching device T5 is turned on (10011), the upper half of the module is put into the corresponding voltage Uc, and the lower half of the module is put into the corresponding voltage Uc. The common input voltage of the commutation sub-unit 11 is 2Uc.

In the second case of normal operation, under the control of the controller, the first switching device T1 is turned on, the second switching device T2 is turned on, the third switching device T3 is turned off, the fourth switching device T4 is turned off, and the fifth switching device T5 When it is turned on (11001), the corresponding voltage Uc of the upper half module is input, and the lower half module is cut out, and the corresponding voltage is 0. The common input voltage of the commutation subunit 11 is Uc.

In the third case of normal operation, under the control of the controller, the first switching device T1 is turned off, the second switching device T2 is turned off, the third switching device T3 is turned on, the fourth switching device T4 is turned on, and the fifth switching device T5 Conduction (00111), the corresponding voltage Uc of the lower half of the module is input, and the upper half of the module is cut out, and the corresponding voltage is 0. The common input voltage of the commutation subunit 11 is Uc.

In the fourth case of normal operation, under the control of the controller, the first switching device T1 is turned off, the second switching device T2 is turned on, the third switching device T3 is turned on, the fourth switching device T4 is turned off, and the fifth switching device T5 Conduction (01101), the upper half of the module is cut out, and the corresponding voltage is 0. The lower half of the module is cut out, and the corresponding voltage is 0. The common input voltage of the commutation subunit 11 is 0.

Therefore, when the circuit is running normally without failure, the controller can control the first switching device T1 and the second switching device T2 to alternately turn on the third switching device T3 and the fourth switching device T4 to even out the switching loss.

When a fault occurs in the circuit, the controller controls the first switching device T1 to the fifth switching device T5 to be locked (turned off), so as to cut off the short-circuit current and isolate the fault.

Preferably, in the AC/DC conversion circuit in this embodiment, the commutation subunit 11 includes at least one combined commutation subcircuit.

The combined commutation sub-circuit is composed of any two or more combinations of the first commutation sub-circuit, the second commutation sub-circuit, the third commutation sub-circuit and the fourth commutation sub-circuit.

Specifically, the commutation sub-unit 11 in each conversion branch can be a first commutation sub-circuit, a second commutation sub-circuit, a third commutation sub-circuit, a fourth commutation sub-circuit or a combined commutation sub-circuit Any one of the circuits may also be a combined structure formed by any combination of the above five or structures with the same function.

Preferably, in the AC-DC conversion circuit in this embodiment, the first switching device T1, the second switching device T2, the third switching device T3, the fourth switching device T4 and the fifth switching device T5 can be selected from insulated gate bipolar transistors . The insulated gate bipolar transistor combines the advantages of MOSFET and GTR, and has the advantages of high input impedance, fast switching speed, simple driving circuit, low on-state voltage, and can withstand high voltage and high current. Of course, devices with switching functions such as triodes, thyristors, and MOS transistors, or series-parallel connections of the above-mentioned switching devices can also be selected.

Preferably, as shown in FIG. 7, the AC-DC conversion circuit in this embodiment further includes at least one DC capacitor, which is connected with the output terminal of the AC/DC conversion unit 14 or the output of the AC/DC conversion unit 14 after being connected in series or in parallel. The terminal is connected, and the output terminal of the DC capacitor is used as an isolation conversion DC interface. Specifically, by connecting a DC capacitor to the output end of the AC/DC conversion unit 14 , power fluctuations can be further offset to make the output isolated and converted DC more stable. Moreover, most of the power fluctuations have been canceled out by the coupling unit 13, and the DC capacitor only needs to select a DC capacitor with a very small capacitance.

Preferably, in the AC-DC conversion circuit in this embodiment, the total positive poles of the cascaded-connected converter subunits 11 of each phase are connected together as the positive pole of the DC interface, and the total negative poles of the cascaded-connected converter subunits 11 of each phase are Connect together as the negative pole of the DC interface.

Preferably, the AC-DC conversion circuit in this embodiment further includes a second DC/AC conversion unit connected to the isolated conversion DC interface, and the output end of the second DC/AC conversion unit is used as the isolation conversion AC interface. Specifically, the second DC/AC conversion unit may select any DC/AC conversion circuit in the prior art to invert the isolated and converted direct current output by the isolated and converted direct current interface into low-voltage alternating current.

The AC-DC conversion circuit in this embodiment can have an AC interface, a DC interface, an isolation conversion DC interface and an isolation conversion AC interface at the same time, and can meet the requirements of various application occasions such as medium and low voltage DC distribution networks.

Example 2

This embodiment provides a power electronic transformer, including the AC-DC conversion circuit in Embodiment 1.

In the power electronic transformer in this embodiment, the AC-DC conversion circuit in it can couple and add the three-phase instantaneous power through the coupling unit, which effectively cancels the fluctuation of the fundamental frequency and the double frequency on the bridge arms of each phase, and there is no need to suppress Installing a large-capacity capacitor on each commutation sub-unit for single-phase fluctuating power greatly reduces the volume of the AC-DC conversion circuit, which can effectively reduce the volume of the power electronic transformer and reduce its cost.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (12)

1. an ac-dc conversion circuit, it is characterised in that include least one set AC-DC conversion module (1), often organize described friendship DC conversion modules (1) includes that at least one converting branch, every described converting branch include:

Multiple change of current subelements (11), the most corresponding three-phase alternating current；

Multiple DC/AC converting units (12), sub with the DC side of described change of current subelement (11) or the described change of current respectively The DC side rear total DC side constituted in series or in parallel of unit (11) connects；

Coupling unit (13), by every mutually in the instantaneous power coupling that exports of a described DC/AC converting unit (12) be added with Eliminate single-phase in the fluctuation of described instantaneous power；

At least one AC/DC converting unit (14), is connected with one or more outfan of described coupling unit (13)；

And between the adjacent described change of current subelement (11) of same phase, cascade connects in described AC-DC conversion module (1), exchange connects The AC of the mouth described change of current subelement (11) from mutually is drawn, and connects with the alternating current of corresponding phase.

Ac-dc conversion circuit the most according to claim 1, it is characterised in that the AC/DC in every described converting branch The outfan of converting unit (14) is in series or in parallel, and by the described AC/DC converting unit (14) after in series or in parallel Outfan is as isolation conversion DC interface.

Ac-dc conversion circuit the most according to claim 1, it is characterised in that described coupling unit (13) includes at least one Individual transformator, the former avris of described transformator includes multiple primary side winding, and a most corresponding described DC/AC conversion is single Unit's outfan of (12) or a multiple DC/AC converting unit (12) in series or in parallel after total outfan connect, secondary Side includes at least 1 vice-side winding, the outfan of each described vice-side winding or multiple described vice-side winding series connection or also Outfan after connection, as the outfan of described coupling unit (13), is connected with the input of described AC/DC converting unit (14).

Ac-dc conversion circuit the most according to claim 1, it is characterised in that described change of current subelement (11) includes at least One the first change of current electronic circuit, described first change of current electronic circuit include the first switching device (T1), second switch device (T2), One diode (D1) and the second diode (D2)；

Described first switching device (T1) and described second switch device (T2) series connection, described first diode (D1) and described the Two diodes (D2) respectively with described first switching device (T1) and described second switch device (T2) inverse parallel, described first opens Close device (T1) and the common port of described second switch device (T2) changes as described with the anode of described second diode (D2) The AC of stream subelement (11), the negative electrode of described first diode (D1) and the anode of described second diode (D2) are as institute State the DC side of change of current subelement (11).

Ac-dc conversion circuit the most according to claim 1, it is characterised in that described change of current subelement (11) includes at least One the second change of current electronic circuit, described second change of current electronic circuit include the first switching device (T1), second switch device (T2), Three switching devices (T3), the 4th switching device (T4), the first diode (D1), the second diode (D2), the 3rd diode (D3) With the 4th diode (D4)；

The series arm of described first switching device (T1) and described 3rd switching device (T3) and described second switch device (T2) it is connected in parallel with the series arm of described 4th switching device (T4), described first diode (D1), described two or two pole Pipe (D2), described 3rd diode (D3) and described 4th diode (D4) respectively with described first switching device (T1), described Second switch device (T2), described 3rd switching device (T3) and described 4th switching device (T4) inverse parallel, described first opens Close common port and described second switch device (T2) and described 4th switch of device (T1) and described 3rd switching device (T3) The common port of device (T4) as the AC of described change of current subelement (11), said two series arm be connected in parallel after public affairs End is as the DC side of described change of current subelement (11) altogether.

Ac-dc conversion circuit the most according to claim 1, it is characterised in that described change of current subelement (11) includes at least One the 3rd change of current electronic circuit, described 3rd change of current electronic circuit include the first switching device (T1), second switch device (T2), Three switching devices (T3), the first diode (D1), the second diode (D2), the 3rd diode (D3) and the 4th diode (D4)；

Described first switching device (T1) and described second switch device (T2) are connected in series, described first diode (D1) and institute State the second diode (D2) respectively with described first switching device (T1) and described second switch device (T2) inverse parallel, described Three diodes (D3) and described 3rd switching device (T3) inverse parallel, and the anode of described 3rd diode (D3) is simultaneously with described The anode of the second diode (D2) connects, the negative electrode of described 3rd diode (D3) simultaneously with the sun of described 4th diode (D4) Pole connects, and the negative electrode of described 4th diode (D4) is connected with the negative electrode of described first diode (D1), described first derailing switch The common port of part (T1) and described second switch device (T2) changes as described with the colelctor electrode of described 3rd switching device (T3) The AC of stream subelement (11), the negative electrode of described first diode (D1) and the anode of described 3rd diode (D3) are as institute State the DC side of change of current subelement (11).

Ac-dc conversion circuit the most according to claim 1, it is characterised in that described change of current subelement (11) includes at least One the 4th change of current electronic circuit, described 4th change of current electronic circuit include the first switching device (T1), second switch device (T2), Three switching devices (T3), the 4th switching device (T4), the 5th switching device (T5), the first diode (D1), the second diode (D2), the 3rd diode (D3), the 4th diode (D4), the 5th diode (D5), the 6th diode (D6) and the 7th diode (D7)；

Described first switching device (T1) and described 3rd switching device (T3) are connected in series, described first diode (D1) and institute State the 3rd diode (D3) respectively with described first switching device (T1) and described 3rd switching device (T3) inverse parallel；Described Two switching devices (T2) and described 4th switching device (T4) are connected in series, described second diode (D2) and described four or two pole Pipe (D4) respectively with described second switch device (T2) and described 4th switching device (T4) inverse parallel；Described 5th switching device (T5) emitter stage is connected with the anode of described 3rd diode (D3), and the colelctor electrode of described 5th switching device (T5) is with described The negative electrode of the second diode (D2) connects, described 5th diode (D5) and described 5th switching device (T5) inverse parallel；Described The anode of the 6th diode (D6) is connected with the negative electrode of described 5th diode (D5), the negative electrode of described 6th diode (D6) with The negative electrode of described first diode (D1) connects, the anode of described 7th diode (D7) and the sun of described 4th diode (D4) Pole connects, and the negative electrode of described 7th diode (D7) is connected with the anode of described 3rd diode (D3), described first derailing switch The common port of part (T1) and described 3rd switching device (T3) and described second switch device (T2) and described 4th switching device (T4) common port is as the AC of described change of current subelement (11), the negative electrode and the described 3rd of described first diode (D1) The anode of diode (D3) as a DC side of described change of current subelement (11), the negative electrode of described second diode (D2) and The anode of described 4th diode (D4) is as another DC side of described change of current subelement (11).

8. according to the ac-dc conversion circuit described in any one of claim 4-7, it is characterised in that described change of current subelement (11) Change of current electronic circuit is combined including at least one；

Described combination change of current electronic circuit is by described first change of current electronic circuit, described second change of current electronic circuit, described 3rd change of current Any two or multiple combination in circuit and described 4th change of current electronic circuit are constituted.

Ac-dc conversion circuit the most according to claim 2, it is characterised in that also include at least one direct current capacitors, With the outfan of described AC/DC converting unit (14), or in series or in parallel after described AC/DC converting unit (14) defeated Go out end to connect, and using the outfan of described direct current capacitors as isolation conversion DC interface.

Ac-dc conversion circuit the most according to claim 1, it is characterised in that often cascade the described change of current of connection mutually Total positive pole of unit (11) is connected together as the positive pole of DC interface, cascades the described change of current subelement (11) of connection mutually Total negative pole be connected together as the negative pole of DC interface.

11. according to the ac-dc conversion circuit described in any one of claim 1-10, it is characterised in that also include the 2nd DC/AC Converting unit, is connected with described isolation conversion DC interface, and using the outfan of described 2nd DC/AC converting unit as isolation Conversion exchange interface.

12. 1 kinds of electric power electric transformers, it is characterised in that include the ac-dc conversion electricity described in any one of claim 1-10 Road.