WO2022160930A1

WO2022160930A1 - Active commutated hybrid converter topology structure and control method therefor

Info

Publication number: WO2022160930A1
Application number: PCT/CN2021/135127
Authority: WO
Inventors: 杨俊�; 魏晓光; 李婷婷; 丁骁; 张娟娟
Original assignee: 全球能源互联网研究院有限公司
Priority date: 2021-02-01
Filing date: 2021-12-02
Publication date: 2022-08-04
Also published as: CN112803796A

Abstract

The present application discloses an active commutated hybrid converter topology structure and a control method therefor. Said topology structure comprises: a three-phase six-bridge arm circuit, wherein each phase bridge arm circuit of the three-phase six-bridge arm circuit comprises an upper bridge arm and a lower bridge arm, and a thyristor valve is provided on each of the upper bridge arm and the lower bridge arm; an upper bridge arm auxiliary valve, a first end thereof being connected to a cathode end of the thyristor valve of each phase upper bridge arm; a lower bridge arm auxiliary valve, a first end thereof being connected to an anode end of the thyristor valve of each phase lower bridge arm; a controllable switch module, a first end thereof being connected to a second end of the upper bridge arm auxiliary valve and a second end of the lower bridge arm auxiliary valve respectively; and a selection unit, comprising two connection ends and at least two selection ends, wherein the connection ends are connected to a second end of the controllable switch module, a first selection end is connected to an anode end of the thyristor valve of the upper bridge arm, and a second selection end is connected to a cathode end of the thyristor valve of the lower bridge arm. By implementing the present application, the occurrence of commutation failure is avoided, and the stability and safety of the operation of grid are ensured.

Description

An active commutation hybrid converter topology and its control method

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on the Chinese patent application with the application number of 202110139044.2, the application date of February 1, 2021, and the application title of "An Actively Commutated Hybrid Converter Topology and Control Method", and requests the Chinese patent application The priority of the patent application, the entire content of the Chinese patent application is hereby incorporated by reference into this application.

technical field

The present application relates to the technical field of commutation in power electronics, in particular to an active commutation hybrid converter topology and a control method thereof.

Background technique

The traditional line commutated converter high voltage direct current (LCC-HVDC) transmission system has the advantages of long-distance large-capacity power transmission and controllable active power, and is widely used in the world. As the core equipment of DC transmission, the converter is the core functional unit to realize the conversion of AC and DC power, and its operational reliability largely determines the operational reliability of the UHV DC power grid.

Since traditional converters mostly use half-controlled thyristors as the core components to form a six-pulse bridge commutation topology, each bridge arm is composed of multi-stage thyristors and their buffer components in series. Commutation failure is prone to occur in the case of faults, resulting in a surge of DC current and a rapid and large loss of DC transmission power, which affects the stable and safe operation of the power grid.

SUMMARY OF THE INVENTION

In view of this, the embodiments of the present application provide an active commutation hybrid converter topology structure and a control method thereof, so as to solve the problem that the commutation failure affects the stable and safe operation of the power grid.

According to a first aspect, this embodiment provides an active commutation hybrid converter topology structure, the topology structure is connected to an AC power grid through a converter transformer, and the topology structure includes: a three-phase six-arm circuit, Each phase bridge arm circuit of the three-phase six bridge arm circuit includes an upper bridge arm and a lower bridge arm, and the upper bridge arm or the lower bridge arm is provided with a thyristor valve; the upper bridge arm auxiliary valve, the first end of which is connected to The cathode end of the thyristor valve of the upper arm of each phase; the auxiliary valve of the lower arm, the first end of which is connected to the anode end of the thyristor valve of the lower arm of each phase; the controllable switch module, the first end of which is connected to the auxiliary valve of the upper arm The second end of the lower bridge arm auxiliary valve is respectively connected with the second end of the lower bridge arm auxiliary valve; the selection unit includes two connection ends and at least two selection ends, the first connection end is connected with the second end of the controllable switch module; the first connection end is connected with the second end of the controllable switch module; The two connection ends are connected to the output end of the converter transformer; the first selection end is connected to the anode end of the thyristor valve of the upper bridge arm, and the second selection end is connected to the cathode end of the thyristor valve of the lower bridge arm.

In combination with the first aspect, in the first embodiment of the first aspect, the controllable switch module includes: at least one shut-off valve, and the at least one shut-off valve is arranged in series.

With reference to the first embodiment of the first aspect and the second embodiment of the first aspect, the shut-off valve includes: a first branch, a first power device is disposed on the first branch, and the first power device It is a fully-controlled power electronic device; the second branch is connected in parallel with the first branch, and the second branch is provided with a first capacitive element and the first power device, and the first power device and all The first capacitive elements are connected in series.

With reference to the first embodiment of the first aspect and the third embodiment of the first aspect, the shut-off valve includes: a third branch, and the third branch is a full-bridge circuit formed by connecting four second power devices ; the second power device is a fully-controlled power electronic device; the fourth branch, a second capacitive element is arranged on the fourth branch, and the second capacitive element is connected in parallel with the upper half bridge of the full-bridge circuit and the lower half bridge.

In combination with the first aspect, in the fourth embodiment of the first aspect, the selection unit is a two-way valve.

With reference to the fourth embodiment of the first aspect, in the fifth embodiment of the first aspect, the two-way valve includes: at least one first thyristor, the at least one thyristor is connected in forward and reverse parallel; the first thyristor is a unidirectional thyristor or A triac; a first buffer part, connected in parallel or in series with the at least one thyristor.

With reference to the fourth embodiment of the first aspect and the sixth embodiment of the first aspect, the two-way valve includes: a first selection branch including at least one third power device, and the at least one third power device is arranged in series; The third power device is a fully-controlled power electronic device; the second selection branch is inversely parallel with the first selection branch, and the second selection branch has the same structure as the first selection branch.

In combination with the fourth embodiment of the first aspect and the seventh embodiment of the first aspect, the two-way valve includes: a third selection branch, which is provided with a plurality of first diodes connected in series; a fourth selection branch, which is connected with all the first diodes. The structure of the third selection branch is the same; the fifth selection branch is connected in parallel between the third selection branch and the fourth selection branch, and the fifth selection branch is provided with a plurality of first selection branches in series Four power devices, the fourth power device is a fully controlled power electronic device.

In combination with the first aspect, in the eighth embodiment of the first aspect, the upper bridge arm auxiliary valve and the lower bridge arm auxiliary valve have the same structure; the upper bridge arm auxiliary valve includes: a first auxiliary branch, the The first auxiliary branch includes: at least one fifth power device, the at least one fifth power device is arranged in series; or, at least two fifth power devices, the at least two fifth power devices are arranged in series in forward and reverse directions; Or, at least one fifth power device, and at least one second diode in series with the at least one fifth power device; or, at least one fifth power device, and in series with the at least one fifth power device At least one second thyristor; and a second buffer component, connected in parallel or in series with the first auxiliary branch.

With reference to the first aspect, in the ninth embodiment of the first aspect, the upper bridge arm auxiliary valve and the lower bridge arm auxiliary valve have the same structure; the upper bridge arm auxiliary valve includes: a second auxiliary branch, the At least one sixth power device is arranged on the second auxiliary branch, the at least one sixth power device is arranged in series, and the sixth power device is a fully controlled power electronic device; the third auxiliary branch is connected to the second auxiliary branch. The auxiliary branch has the same structure and is connected in parallel with the second auxiliary branch; the third buffer component is connected in parallel with the second auxiliary branch and the third auxiliary branch.

In combination with the first aspect, in the tenth embodiment of the first aspect, the structures of the upper bridge arm auxiliary valve and the lower bridge arm auxiliary valve are the same; the upper bridge arm auxiliary valve includes: a fourth auxiliary branch, which is provided with a plurality of second diodes connected in series; a fifth auxiliary branch, the structure of which is consistent with the fourth auxiliary branch, and is connected in parallel with the fourth auxiliary branch; the sixth auxiliary branch is connected in parallel with the fourth auxiliary branch Between the fourth auxiliary branch and the fifth auxiliary branch, a plurality of seventh power devices connected in series are arranged on the sixth auxiliary branch, and the seventh power device is a fully-controlled power electronic device.

In combination with the first aspect, in the eleventh embodiment of the first aspect, the upper bridge arm auxiliary valve and the lower bridge arm auxiliary valve have the same structure; the upper bridge arm auxiliary valve includes: a seventh auxiliary branch, which is provided with There is at least one eighth power device, the at least one eighth power device is arranged in series, and the eighth power device is a fully-controlled power electronic device; the eighth auxiliary branch is connected in parallel with the seventh auxiliary branch, so The eighth auxiliary branch is provided with at least one ninth power device and a third capacitive element, the at least one ninth power device is provided in series with the third capacitive element, and the at least one ninth power device is provided in series, The ninth power device is a fully controlled power electronic device.

In combination with the first aspect, in the twelfth embodiment of the first aspect, the thyristor valve includes: a plurality of thyristors; and a plurality of fourth buffer components, respectively connected in series or in parallel with the plurality of thyristors.

In combination with the fifth embodiment or the eighth embodiment or the ninth embodiment or the twelfth embodiment of the first aspect, in the thirteenth embodiment of the first aspect, the first buffer member, the second buffer member, the third buffer member and the Each of the fourth buffer components includes: a first buffer branch composed of a capacitor; or, a second buffer branch connected in series with a resistor and the capacitor; or, a third buffer branch connected in parallel with the capacitor and the resistor; or , the resistor and the fifth diode are connected in parallel, and then connected in series with the capacitor to form a fourth buffer branch; or, the resistor and the capacitor are connected in parallel, and then connected in series with the fifth diode to form a fourth buffer five buffer branches; or, the sixth buffer branch composed of arresters; or, the first buffer branch, the second buffer branch, the third buffer branch, the fourth buffer branch, A plurality of the fifth buffer branch and the sixth buffer branch are formed in parallel to form a seventh buffer branch.

According to a second aspect, an embodiment of the present application provides a control method for an active commutation hybrid converter topology, which is used for the active commutation hybrid converter according to the first aspect or any embodiment of the first aspect. converter topology structure, the method includes: turning off the controllable switch module connected to the i-th bridge arm of the active commutation hybrid converter topology structure, the selection unit and the auxiliary valve of the upper bridge arm or the lower bridge arm Auxiliary valve; turn on the thyristor valve of the ith bridge arm; after one control cycle, return to the step of turning on the thyristor valve of the ith bridge arm; wherein, i∈[1,6].

With reference to the second aspect, in the first embodiment of the second aspect, the method further includes: when detecting that the ith bridge arm has a commutation failure or a short-circuit fault, turning on the ith bridge The selection unit connected to the arm and the auxiliary valve of the upper bridge arm or the auxiliary valve of the lower bridge arm connected to the i-th bridge arm; triggering the controllable switch module to output the reverse voltage to the thyristor valve of the i-th bridge arm, and performing the i-th bridge arm The commutation of each bridge arm to the upper bridge arm or the lower bridge arm connected to it; when the current of the ith bridge arm is reduced to zero, the upper bridge arm auxiliary valve or the lower bridge connected to the ith bridge arm is turned off. Arm auxiliary valve.

The technical solution of the present application has the following advantages:

1. The active commutation hybrid converter topology structure provided in the embodiment of the present application, the introduction of a controllable switch module into the hybrid converter can transfer the bridge arm current in advance when the bridge arm commutation fails or fails, and at the same time. The reverse voltage is provided for the bridge arm, which increases the commutation time area of the thyristor to ensure its reliable turn-off. The controllable switch module is used to realize the current transfer, and the selection unit is subjected to the voltage stress, so that the auxiliary valve of the upper bridge arm and the auxiliary valve of the lower bridge arm participate in the commutation, which avoids the occurrence of commutation failure, thereby ensuring the stability of the power grid operation. safety.

2. The active commutation hybrid converter topology structure provided by the embodiment of the present application includes a three-phase six-arm circuit, and each phase arm includes an upper arm and a lower arm respectively, and each upper arm or lower arm. There are corresponding upper bridge arm auxiliary valve or lower bridge arm auxiliary valve. The active commutation hybrid converter topology can turn on the auxiliary valve of the upper bridge arm or the auxiliary valve of the lower bridge arm at any time, effectively reducing the loss of the bridge arm of each phase.

3. The control method of the hybrid inverter topology structure of the active commutation provided by the embodiment of the present application, by turning off the controllable switch module connected to the i-th bridge arm of the hybrid inverter topology structure of the active commutation , select the unit and the auxiliary valve of the upper bridge arm or the auxiliary valve of the lower bridge arm; turn on the thyristor valve of the ith bridge arm; after a control cycle, return to the step of turning on the thyristor valve of the ith bridge arm; wherein , i∈[1,6]. This enables the active commutation hybrid converter topology to work in the normal operating mode.

4. The control method of the active commutation hybrid converter topology provided in the embodiment of the present application, when the commutation fails or the short-circuit fault, the hybrid converter topology triggers the active commutation operation mode, avoiding the commutation. When the phase failure occurs, and when the commutation process of the hybrid converter returns to normal, the controllable switch module, the selection unit and the auxiliary valve of the upper bridge arm or the auxiliary valve of the lower bridge arm are closed, and the bridge arms of each phase operate normally independently, thereby The realization ensures that the selection unit and the auxiliary valve of the upper bridge arm or the auxiliary valve of the lower bridge arm only bear the turn-off voltage stress when the commutation fails or fails, which reduces the loss of the device, thereby prolonging the service life of the device.

Description of drawings

The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, these drawings illustrate the embodiments consistent with the present application, and together with the specification, are used to explain the technical solutions of the present application.

FIG. 1 is a structural diagram of a hybrid converter topology with active commutation according to an embodiment of the present application;

2 is a structural block diagram of a thyristor valve according to an embodiment of the present application;

3 is a structural block diagram of a shut-off valve according to an embodiment of the present application;

Fig. 4 is another structural block diagram of a shut-off valve according to an embodiment of the present application;

5 is a structural block diagram of a two-way valve according to an embodiment of the present application;

Fig. 6 is another structural block diagram of the two-way valve according to the embodiment of the present application;

Fig. 7 is another structural block diagram of the two-way valve according to the embodiment of the present application;

8 is a structural block diagram of an upper/lower bridge arm auxiliary valve according to an embodiment of the present application;

9 is another structural block diagram of the upper/lower bridge arm auxiliary valve according to an embodiment of the present application;

10 is another structural block diagram of the upper/lower bridge arm auxiliary valve according to an embodiment of the present application;

11 is another structural block diagram of the upper/lower bridge arm auxiliary valve according to an embodiment of the present application;

12 is a structural block diagram of a buffer component according to an embodiment of the present application;

13 is a flowchart of a control method for an active commutation hybrid converter topology structure according to an embodiment of the present application;

14 is a schematic diagram of a trigger signal according to an embodiment of the present application;

15 is a trigger control sequence in the first working mode according to an embodiment of the present application;

16 is a trigger control sequence in the second working mode according to an embodiment of the present application;

FIG. 17 is a current flow path for periodic triggering of the V1 thyristor valve during normal operation according to an embodiment of the present application;

18 is a current flow path for the thyristor valve to be turned off and the upper bridge arm auxiliary valve to flow through according to an embodiment of the present application;

19 is a current flow path for the thyristor valve to be turned off and the upper arm auxiliary valve to be turned off according to an embodiment of the present application.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of this application.

As the core equipment of DC transmission, the converter is the core functional unit to realize the conversion of AC and DC power, and its operational reliability largely determines the operational reliability of the UHV DC power grid. However, since traditional converters mostly use half-controlled thyristors as the core components to form a six-pulse bridge commutation topology, each bridge arm is composed of multi-stage thyristors and their buffer components in series. In the case of AC system failure, commutation failure is prone to occur, resulting in a surge in DC current and a rapid and large loss of DC transmission power, which affects the stable and safe operation of the power grid.

Based on this, the technical solution of the present application introduces a shut-off control valve on the AC side to ensure that the thyristor valve has sufficient reverse recovery time for reliable shut-off, and at the same time uses the auxiliary valve branch to assist the commutation to fundamentally solve the DC system. commutation failure problem, thus ensuring the stable and safe operation of the power grid.

According to an embodiment of the present application, an embodiment of an actively commutated hybrid converter topology structure is provided, and the actively commutated hybrid converter topology structure is connected to an AC power grid through a converter transformer, as shown in FIG. 1 . As shown, the active commutation hybrid converter topology includes: a three-phase six-arm circuit, an upper arm auxiliary valve, a lower arm auxiliary valve, a controllable switch module and a selection unit. Wherein, each phase bridge arm circuit of the three-phase six bridge arm circuit includes an upper bridge arm and a lower bridge arm, and both the upper bridge arm or the lower bridge arm are provided with thyristor valves. The first end of the auxiliary valve of the upper bridge arm is connected to the cathode end of the thyristor valve of the upper bridge arm of each phase, and the first end of the auxiliary valve of the lower bridge arm is connected to the anode end of the thyristor valve of the lower bridge arm of each phase; the first end of the controllable switch module are respectively connected with the second end of the auxiliary valve of the upper bridge arm and the second end of the auxiliary valve of the lower bridge arm; the selection unit includes two connection ends and at least two selection ends, and the connection ends are connected with the second end of the controllable switch module , the first selection end is connected to the anode end of the thyristor valve of the upper bridge arm, and the second selection end is connected to the cathode end of the thyristor valve of the lower bridge arm. For a three-phase six-arm circuit, the first connection end of the selection unit may include three connection ports, which are respectively connected with the second end of the auxiliary valve of the upper arm and the second end of the auxiliary valve of the lower arm; similarly, The second connection end of the selection unit may also include three connection ports, which are respectively connected to the three-phase output end of the converter transformer. The ports of the first connection end and the second connection end of the selection unit are not limited here, and those skilled in the art can determine them according to actual needs.

As shown in Figure 1, one end of the three-phase six-arm circuit is connected to the positive electrode of the DC bus, and the other end is connected to the negative electrode of the DC bus. The selection unit 200 may be a two-way valve, and two-way valves DVa, DVb and DVc are respectively set on the AC bus of each phase of the three-phase six-bridge arm. The three-phase six-arm circuit includes V1 valve, V2 valve, V3 valve, V4 valve, V5 valve and V6 valve. Among them, the V1 valve, the V3 valve and the V5 valve are the upper bridge arm 110, and each upper bridge arm 110 is provided with a thyristor valve; the V2 valve, the V4 valve and the V6 valve are the lower bridge arm 120, and each lower bridge arm is 120 are provided with thyristor valves.

Vp is the auxiliary valve of the upper bridge arm, and the first end of Vp is connected to the cathode ends of the thyristor valves in the V1 valve, V3 valve and V5 valve respectively; Vn is the auxiliary valve of the lower bridge arm, and the first end of Vn is connected to the V2 valve, The anode ends of the thyristor valves of the V4 valve and the V6 valve are connected; DVM is a controllable switch module, the first end of which is respectively connected with the first connection ends of the two-way valves DVa, DVb and DVc, and the second end is respectively connected with the second end of Vp. terminal is connected to the second terminal of Vn.

The second connection terminals of the two-way valves DVa, DVb and DVc are respectively connected with the a-phase output terminal, the b-phase output terminal and the c-phase output terminal of the converter transformer; the first selection terminal of the two-way valve DVa is connected with the positive terminal of the thyristor valve in the V1 valve. Extreme connection; the second selection end of the two-way valve DVa is connected with the cathode end of the thyristor valve in the V4 valve; the first selection end of the two-way valve DVb is connected with the anode end of the thyristor valve in the V3 valve; the second selection end of the two-way valve DVb is connected to The cathode end of the thyristor valve in the V6 valve is connected; the first selection end of the bidirectional valve DVc is connected with the anode end of the thyristor valve in the V5 valve; the second selection end of the bidirectional valve DVc is connected with the cathode end of the thyristor valve in the V2 valve.

In the hybrid converter topology with active commutation provided by the embodiment of the present application, a controllable switch module is introduced into the hybrid converter, so that the bridge arm current can be transferred in advance when the bridge arm commutation fails or fails, and at the same time, it is a bridge arm. The arm provides a reverse voltage, which increases the commutation time area of the thyristor to ensure its reliable turn-off. The controllable switch module is used to realize the current transfer, and the selection unit is subjected to the voltage stress, so that the auxiliary valve of the upper bridge arm and the auxiliary valve of the lower bridge arm participate in the commutation, which avoids the occurrence of commutation failure, thereby ensuring the stability of the power grid operation. safety.

In some embodiments, the thyristor valve includes at least one thyristor and a fourth buffer member connected in parallel or in series with the thyristor, respectively, wherein the at least one thyristor is arranged in series, and the fourth buffer member is configured as a thyristor device to prevent damage from high voltage and high current. As shown in FIG. 2 , the thyristor valve includes at least one thyristor 311 to 31n and fourth buffer parts 411 to 41n connected in parallel with the thyristor, respectively.

In some embodiments, the controllable switch module may be a controllable capacitor module, configured as a bidirectional voltage output, capable of forcibly transferring the current in the thyristor valve of each arm of the three-phase six-arm circuit to the auxiliary valve of the upper arm or the lower arm Auxiliary valves, and thyristor valves provide reverse recovery voltage.

In some embodiments, the controllable switch module includes at least one shut-off valve arranged in series. The shut-off valve may include at least one first power unit and a first buffer component respectively connected in parallel with the first power unit (those skilled in the art can know the parallel connection manner, which is not shown in the figure), wherein the at least one first power unit is connected in parallel. A power unit is arranged in series, and the first buffer component is configured to limit voltage and current stress.

In some embodiments, as shown in FIG. 3 , the first power unit 711 may be a power electronic unit composed of a first branch and a second branch.

The first branch is provided with the first power device 511; the second branch is connected in parallel with the first branch, and the second branch is provided with the first capacitive element 611 and the first power device 511, the first power device 511 and the first capacitor Elements 611 are connected in series. Wherein, the first power device 511 is a fully controlled power electronic device, and the fully controlled power electronic device is an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT), an integrated gate commutated thyristor (Intergrated Gate Commutated Thyristors, IGCT), Injection Enhanced Gate Transistor (IEGT), Gate-Turn-Off Thyristor (GTO) or Metal-Oxide-Semiconductor Field Effect Transistor, MOSFET), etc., can turn off one or more of the devices. It should be noted that, if the fully-controlled power electronic device does not have a reverse voltage blocking function, a diode needs to be connected in reverse parallel to the fully-controlled power electronic device.

In some embodiments, as shown in FIG. 4 , the first power unit 711 may also be a power electronic unit composed of a third branch and a fourth branch.

The third branch is a full-bridge circuit formed by connecting four second power devices 521; the fourth branch is provided with a second capacitive element 621, and the second capacitive element 621 is connected in parallel between the upper half-bridge and the lower half-bridge of the full-bridge circuit . The second power device 521 is a fully controlled power electronic device, and the fully controlled power electronic device is one or more of IGBT, IGCT, IEGT, GTO or MOSFET. It should be noted that, if the fully-controlled power electronic device does not have a reverse voltage blocking function, a diode needs to be connected in reverse parallel to the fully-controlled power electronic device.

The above-mentioned shut-off valve has bidirectional voltage controllable output capability, and is mainly used to shut off the current of the thyristor branch circuit and provide it with a reverse voltage, so as to ensure that the thyristor valve of the thyristor branch circuit has sufficient off time for reliable shutdown. The application does not limit the topological form of the shut-off valve, as long as it is a topological form with the function of bidirectional voltage controllable output.

In some embodiments, the selection units are three two-way valves, capable of two-way opening and two-way pressure resistance. The three two-way valves are respectively arranged in each phase of the three-phase six-arm circuit, and the upper arm and the lower arm of each phase share a two-way valve. In some embodiments, taking the two-way valve DVa as an example, as shown in FIG. 5 , the two-way valve DVa may include: at least one first thyristor 321 - 32n and a first buffer connected in parallel or in series with the at least one first thyristor 321 - 32n part. Among them, at least one of the first thyristors 321-32n is divided into two circuits and connected in parallel in forward and reverse directions to ensure that they can conduct bidirectional conduction and withstand voltage in both directions. The first thyristors 321 to 32n may be unidirectional thyristors or bidirectional thyristors, which are not specifically limited here.

In some embodiments, taking the two-way valve DVa as an example, as shown in FIG. 6 , the two-way valve DVa may include: a first selection branch and a second selection branch.

The first selection branch includes at least one third power device 531-53n, and at least one third power device 531-53n is arranged in series. The third power device here is a fully controlled power electronic device, and the fully controlled power electronic device is one or more of IGBT, IGCT, IEGT, GTO or MOSFET. It should be noted that, if the fully-controlled power electronic device does not have the reverse voltage blocking function, a diode needs to be connected in reverse parallel to the fully-controlled power electronic device to realize the unidirectional voltage blocking function. The structure of the second selection branch is the same as that of the first selection branch, and is inversely connected in parallel with the first selection branch to ensure that it can conduct bidirectional conduction and withstand voltage in both directions.

In some embodiments, taking the two-way valve DVa as an example, as shown in FIG. 7 , the two-way valve DVa may include: a third selection branch, a fourth selection branch, and a fifth selection branch.

The third selection branch is provided with a plurality of first diodes 811-81n connected in series; the fourth selection branch has the same structure as the third selection branch; the fifth selection branch is connected in parallel with the third selection branch and the third selection branch. The fourth option is between branches. The fifth selection branch is provided with a plurality of fourth power devices 541 to 54n connected in series, the fourth power devices 541 to 54n are fully controlled power electronic devices, and the fully controlled power electronic devices are IGBT, IGCT, IEGT, GTO or MOSFET one or more of.

In some embodiments, the upper bridge arm auxiliary valve and the lower bridge arm auxiliary valve have the same structure.

In some embodiments, as shown in FIG. 8 , taking the auxiliary valve of the upper bridge arm as an example, the auxiliary valve of the upper bridge arm includes: a first auxiliary branch and a second buffer member.

Wherein, the second buffer component is configured to limit voltage and current stress. The first auxiliary branch can be formed by at least one fifth power device 551-55n in series; it can also be formed by at least two fifth power devices 551-55n in forward and reverse series; it can also be formed by at least one fifth power device 551-55n and at least one second diode connected in series with at least one fifth power device constitutes 821-82n; it can also be at least one fifth power device 551-55n and at least one first diode connected in series with at least one fifth power device 551-55n Two thyristors constitute 331-33n. The fifth power devices 551 to 55n are fully controlled power electronic devices, and the fully controlled power electronic devices are one or more of IGBT, IGCT, IEGT, GTO or MOSFET. It should be noted that the fully controlled power electronic device It can be a device with bidirectional voltage blocking capability or a device with unidirectional voltage blocking capability. The form of the first auxiliary branch is not limited here.

In some embodiments, as shown in FIG. 9 , taking the auxiliary valve of the upper bridge arm as an example, the auxiliary valve of the upper bridge arm includes: a second auxiliary branch, a third auxiliary branch and a third buffer component.

Wherein, at least one sixth power device 561-56n is arranged on the second auxiliary branch, and at least one sixth power device 561-56n is arranged in series. The third auxiliary branch has the same structure as the second auxiliary branch, and the third auxiliary branch and the second auxiliary branch are arranged in parallel. The third buffer components are respectively arranged in parallel with the second auxiliary branch and the third auxiliary branch. The sixth power device is a fully controlled power electronic device, and the fully controlled power electronic device is one or more of IGBT, IGCT, IEGT, GTO or MOSFET, which is not limited here.

In some embodiments, as shown in FIG. 10 , taking the auxiliary valve of the upper bridge arm as an example, the auxiliary valve of the upper bridge arm includes: a fourth auxiliary branch, a fifth auxiliary branch and a sixth auxiliary branch.

The fourth auxiliary branch is provided with a plurality of first diodes 811-81n connected in series; the fifth auxiliary branch has the same structure as the fourth auxiliary branch; the sixth auxiliary branch is connected in parallel with the fourth auxiliary branch and the fourth auxiliary branch. Between the fifth auxiliary branch. The sixth auxiliary branch is provided with a plurality of seventh power devices 571 to 57n connected in series, the seventh power device is a fully controlled power electronic device, and the fully controlled power electronic device is one of IGBT, IGCT, IEGT, GTO or MOSFET. one or more.

In some embodiments, as shown in FIG. 11 , taking the auxiliary valve of the upper bridge arm as an example, the auxiliary valve of the upper bridge arm includes: a seventh auxiliary branch and an eighth auxiliary branch.

Wherein, at least one eighth power device 581-58n is arranged on the seventh auxiliary branch, and at least one eighth power device is arranged in series. The eighth power devices 581 to 58n are fully controlled power electronic devices, and the fully controlled power electronic devices are one or more of IGBT, IGCT, IEGT, GTO or MOSFET. The eighth auxiliary branch is arranged in parallel with the seventh auxiliary branch. At least one ninth power device 591-59n and a third capacitive element are arranged on the eighth auxiliary branch, and at least one ninth power device is arranged in series with the third capacitance element 631, and at least one ninth power device is arranged in series , the ninth power device is a fully controlled power electronic device, and the fully controlled power electronic device is one or more of IGBT, IGCT, IEGT, GTO or MOSFET.

In some embodiments, the first buffer component, the second buffer component, the third buffer component, and the fourth buffer component are all composed of one or more forms of components such as capacitors, resistance-capacitance loops, diodes, inductors, or arresters.

In some embodiments, as shown in FIG. 12 , the first buffer part, the second buffer part, the third buffer part and the fourth buffer part may be a first buffer branch composed of capacitors; it may be a series connection of a resistor and a capacitor The second buffer branch; it can be the third buffer branch consisting of a capacitor and a resistor in parallel; it can be a fourth buffer branch RCD1 formed by a resistor and a fifth diode in parallel, and then a capacitor in series; it can be a resistor It is connected in parallel with the capacitor, and then connected in series with the fifth diode to form the fifth buffer branch RCD2; it can also be the sixth buffer branch formed by the arrester, or the above-mentioned first buffer branch, second buffer branch, A seventh buffer branch formed in parallel by one or more of the third buffer branch, the fourth buffer branch, the fifth buffer branch and the sixth buffer branch.

According to an embodiment of the present application, an embodiment of a control method for an active commutation hybrid converter topology is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be performed in a computer-controlled The instructions are executed in a computer system and, although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in an order different from that herein.

This embodiment provides a control method for an active commutation hybrid converter topology, which can be used for the above-mentioned active commutation hybrid converter topology. FIG. 13 is a flowchart according to an embodiment of the present application. Figure, as shown in Figure 13, the process includes the following steps:

S11, turn off the controllable switch module, the selection unit and the auxiliary valve of the upper bridge arm or the auxiliary valve of the lower bridge arm connected to the ith bridge arm of the active commutation hybrid converter topology.

S12, turn on the thyristor valve of the i-th bridge arm.

S13, after one control cycle, return to the step of turning on the thyristor valve of the ith bridge arm; wherein, i∈[1,6].

In some embodiments, under normal operating conditions of the hybrid converter topology, the thyristor valve is periodically subjected to voltage and current stress, the upper arm auxiliary valve and the lower arm auxiliary valve are always off, and only in the bridge arm The thyristor valve is subjected to voltage stress when it is turned off.

The control method for the active commutation hybrid converter topology provided in this embodiment is to turn off the controllable switch module and the selection unit connected to the i-th bridge arm of the active commutation hybrid converter topology. with the auxiliary valve of the upper bridge arm or the auxiliary valve of the lower bridge arm; turn on the thyristor valve of the ith bridge arm; after a control cycle, return to the step of turning on the thyristor valve of the ith bridge arm; wherein, i∈ [1,6]. This enables the active commutation hybrid converter topology to work in the normal operating mode.

The phase commutation process of the hybrid converter described above will be jointly described with reference to FIGS. 14 to 19 . Taking the V1 valve to V3 valve commutation in the hybrid converter shown in Figure 1, and the bidirectional valve DVa adopting the thyristor anti-parallel structure as an example, Figure 14 shows the trigger signal description of the relevant circuit, Sg1 and Sg3 are thyristor valves respectively. Trigger signals of V1 and V3, Sga1 is the forward control signal of the two-way valve DVa, Sga2 is the reverse control signal of the two-way valve DVa, Sap is the control signal of the upper bridge arm auxiliary valve Vp, Sgm is the output control of the controllable switch module Signal.

Figure 15 shows the triggering sequence of each valve in the first working mode. During normal operation, the V1 thyristor valve is periodically triggered, and the upper bridge arm auxiliary valve Vp, the two-way valve DVa, and the controllable switch module DVM are all in the off state, and the current is shown in the figure 17 shown. When the commutation failure or short-circuit fault occurs in the V1 valve at time _tf , the bidirectional valve DVa and the auxiliary valve Vp of the upper bridge arm are triggered to turn on, and the controllable switch module DVM is triggered to output the reverse voltage to the bridge arm where V1 is located to achieve The auxiliary bridge arm where the auxiliary valve of the upper bridge arm is located is commutated, as shown in Figure 18. After the current of the bridge arm where the thyristor valve is located crosses zero, the thyristor valve of the bridge arm where the V1 valve is located is turned off and begins to withstand the reverse voltage, and the current of the V1 valve is all transferred to the auxiliary valve of the upper bridge arm, as shown in Figure 19. At the moment of t _f +Δt2, the auxiliary valve Vp of the upper bridge arm starts to be turned off, and all the current is transferred to the V3 valve, completing the commutation of the V1 valve to the V3 valve. The time from the current zero crossing of the bridge arm where the thyristor valve is located to the turn-off of the auxiliary valve Vp of the upper bridge arm is the turn-off time t _off of the thyristor under back pressure, which is controllable and only needs to be greater than the minimum turn-off time of the thyristor. its reliable shutdown. Among them, Δt2 is the delay time for turning off the auxiliary valve of the upper bridge arm.

Figure 16 shows the trigger sequence of each valve in the second working mode. In each working cycle, the V1 valve and the V3 valve start commutation, that is, the V1 valve trigger pulse Sg1 delays 120° to trigger the two-way valve DVa and the upper bridge arm The auxiliary valve Vp, at the same time, triggers the controllable switch module DVM to apply a reverse voltage to the thyristor valve of the bridge arm where the V1 valve is located to realize the commutation of the auxiliary bridge arm where the auxiliary valve of the upper bridge arm is located, as shown in Figure 18 Show. After the current of the bridge arm where the V1 valve is located crosses zero, the thyristor valve of the bridge arm where the V1 valve is located is turned off and withstands the reverse voltage, and the V1 valve current is all transferred to the upper bridge arm auxiliary valve Vp, as shown in Figure 19. After Δt1, the controllable switch module is turned off, and Δt1 is not less than the minimum turn-off time t _off required by the thyristor valve. After Δt2, the auxiliary valve Vp of the upper bridge arm is turned off, and the current is all transferred to the V3 valve to complete the commutation. Since the reverse pressure bearing time of the thyristor valve is controllable, it can ensure that it has enough time to restore the blocking capacity, and the auxiliary valve of the upper bridge arm can be controlled to shut off and can withstand high pressure, which can ensure the smooth completion of the active commutation process, thereby avoiding the need for replacement Phase failure occurs. Among them, Δt1 is the delay time of turning off the controllable switch module, and Δt2 is the delay time of turning off the auxiliary valve of the upper bridge arm.

In the control method of the active commutation hybrid converter topology provided in this embodiment, in the event of a commutation failure or a short-circuit fault, the hybrid converter topology triggers the active commutation operation mode, thereby avoiding the commutation failure. occurs, and when the commutation process of the hybrid converter returns to normal, the controllable switch module, the selection unit and the auxiliary valve of the upper bridge arm or the auxiliary valve of the lower bridge arm are closed, and the bridge arms of each phase operate normally independently, thereby realizing the guarantee of The selection unit and the auxiliary valve of the upper bridge arm or the auxiliary valve of the lower bridge arm only bear the turn-off voltage stress when the commutation fails or fails, which reduces the loss of the device, thereby prolonging the service life of the device.

Although the embodiments of the present application are described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations all fall within the scope of the appended claims within the limits of the requirements.

Claims

An active commutation hybrid converter topology structure, the topology structure is connected to an AC power grid through a converter transformer, and the topology structure includes:

A three-phase six-arm circuit, each phase of the three-phase six-arm circuit includes an upper arm and a lower arm, and a thyristor valve is arranged on the upper arm or the lower arm;

The upper bridge arm auxiliary valve, the first end of which is connected to the cathode end of the thyristor valve of the upper bridge arm of each phase;

The lower bridge arm auxiliary valve, the first end of which is connected to the anode end of the thyristor valve of the lower bridge arm of each phase;

a controllable switch module, the first end of which is respectively connected with the second end of the upper bridge arm auxiliary valve and the second end of the lower bridge arm auxiliary valve;

The selection unit includes two connection ends and at least two selection ends, the first connection end is connected with the second end of the controllable switch module; the second connection end is connected with the output end of the converter transformer; the first selection end is connected with The anode end of the thyristor valve of the upper bridge arm is connected, and the second selection end is connected to the cathode end of the thyristor valve of the lower bridge arm.
The topology of claim 1, wherein the controllable switch module comprises:

At least one shut-off valve is arranged in series.
3. The topology of claim 2, wherein the shut-off valve comprises:

A first branch, where a first power device is disposed on the first branch, and the first power device is a fully-controlled power electronic device;

The second branch is connected in parallel with the first branch, the second branch is provided with a first capacitive element and the first power device, and the first power device and the first capacitive element are connected in series.
3. The topology of claim 2, wherein the shut-off valve comprises:

a third branch, the third branch is a full-bridge circuit formed by connecting four second power devices; the second power device is a fully-controlled power electronic device;

The fourth branch is provided with a second capacitive element, and the second capacitive element is connected in parallel between the upper half-bridge and the lower half-bridge of the full-bridge circuit.
The topology of claim 1, wherein the selection unit is a two-way valve.
6. The topology of claim 5, wherein the two-way valve comprises:

at least one first thyristor, the at least one thyristor is connected in parallel in forward and reverse directions; the first thyristor is a unidirectional thyristor or a bidirectional thyristor;

The first buffer part is connected in parallel or in series with the at least one thyristor.
6. The topology of claim 5, wherein the two-way valve comprises:

The first selection branch includes at least one third power device, and the at least one third power device is arranged in series; the third power device is a fully-controlled power electronic device;

The second selection branch is inversely parallel with the first selection branch, and the second selection branch has the same structure as the first selection branch.
6. The topology of claim 5, wherein the two-way valve comprises:

The third selection branch is provided with a plurality of first diodes connected in series;

a fourth selection branch, which is consistent with the structure of the third selection branch;

A fifth selection branch is connected in parallel between the third selection branch and the fourth selection branch, and a plurality of fourth power devices connected in series are arranged on the fifth selection branch, and the fourth power devices It is a fully controlled power electronic device.
The topology structure according to claim 1, wherein the structure of the auxiliary valve of the upper bridge arm and the auxiliary valve of the lower bridge arm are the same; the auxiliary valve of the upper bridge arm comprises:

A first auxiliary branch, the first auxiliary branch includes: at least one fifth power device, the at least one fifth power device is arranged in series; or, at least two fifth power devices, the at least two fifth power devices The power devices are arranged in forward and reverse series; or, at least one fifth power device, and at least one second diode connected in series with the at least one fifth power device; or, at least one fifth power device, and the at least one fifth power device and the at least one second thyristor connected in series with at least one fifth power device;

The second buffer component is connected in parallel or in series with the first auxiliary branch.
The topology structure according to claim 1, wherein the structure of the auxiliary valve of the upper bridge arm and the auxiliary valve of the lower bridge arm are the same; the auxiliary valve of the upper bridge arm comprises:

a second auxiliary branch, wherein at least one sixth power device is arranged on the second auxiliary branch, the at least one sixth power device is arranged in series, and the sixth power device is a fully-controlled power electronic device;

The third auxiliary branch has the same structure as the second auxiliary branch and is connected in parallel with the second auxiliary branch;

A third buffer component is connected in parallel with the second auxiliary branch and the third auxiliary branch.
The topology structure according to claim 1, wherein the structure of the auxiliary valve of the upper bridge arm and the auxiliary valve of the lower bridge arm are the same; the auxiliary valve of the upper bridge arm comprises:

The fourth auxiliary branch is provided with a plurality of second diodes connected in series;

a fifth auxiliary branch, which has the same structure as the fourth auxiliary branch and is connected in parallel with the fourth auxiliary branch;

The sixth auxiliary branch is connected in parallel between the fourth auxiliary branch and the fifth auxiliary branch, a plurality of seventh power devices connected in series are arranged on the sixth auxiliary branch, and the seventh power device It is a fully controlled power electronic device.
The topology structure according to claim 1, wherein the structure of the auxiliary valve of the upper bridge arm and the auxiliary valve of the lower bridge arm are the same; the auxiliary valve of the upper bridge arm comprises:

The seventh auxiliary branch is provided with at least one eighth power device, the at least one eighth power device is arranged in series, and the eighth power device is a fully-controlled power electronic device;

The eighth auxiliary branch is connected in parallel with the seventh auxiliary branch, the eighth auxiliary branch is provided with at least one ninth power device and a third capacitive element, and the at least one ninth power device is connected with the first Three capacitive elements are arranged in series, the at least one ninth power device is arranged in series, and the ninth power device is a fully controlled power electronic device.
The topology of claim 1, wherein the thyristor valve comprises:

multiple thyristors;

A plurality of fourth buffer components are respectively connected in series or in parallel with the plurality of thyristors.
The topology according to claim 6 or 9 or 10 or 13, wherein the first buffer part, the second buffer part, the third buffer part and the fourth buffer part each comprise:

The first buffer branch composed of capacitors;

Or, a second buffer branch in which a resistor is connected in series with the capacitor;

Or, a third buffer branch in which the capacitor and the resistor are connected in parallel;

Or, the resistor is connected in parallel with the fifth diode, and then connected in series with the capacitor to form a fourth buffer branch;

Or, the resistor and the capacitor are connected in parallel, and then connected in series with the fifth diode to form a fifth buffer branch;

Or, the sixth buffer branch composed of arresters;

Or, among the first buffer branch, the second buffer branch, the third buffer branch, the fourth buffer branch, the fifth buffer branch and the sixth buffer branch A seventh buffer branch formed by a plurality of parallel connections.
A control method for an actively commutated hybrid converter topology, which is used in the actively commutated hybrid converter topology according to any one of claims 1 to 14, the method comprising:

Turn off the controllable switch module, the selection unit and the auxiliary valve of the upper bridge arm or the auxiliary valve of the lower bridge arm connected to the ith bridge arm of the active commutation hybrid converter topology;

Conducting the thyristor valve of the i-th bridge arm;

After one control cycle, return to the step of turning on the thyristor valve of the i-th bridge arm; wherein, i∈[1,6].
The method of claim 15, further comprising:

When it is detected that a commutation failure or a short-circuit fault occurs in the i-th bridge arm, the selection unit connected to the i-th bridge arm and the upper bridge arm auxiliary valve connected to the i-th bridge arm are turned on or Lower bridge arm auxiliary valve;

Trigger the controllable switch module to output the reverse voltage to the thyristor valve of the ith bridge arm, and carry out the commutation of the ith bridge arm to the upper bridge arm or the lower bridge arm connected to it;

When the current of the ith bridge arm is reduced to zero, the upper bridge arm auxiliary valve or the lower bridge arm auxiliary valve connected to the ith bridge arm is turned off.