CN112803797A - Hybrid converter topological structure with direct-current side for assisting phase conversion and control method thereof - Google Patents

Hybrid converter topological structure with direct-current side for assisting phase conversion and control method thereof Download PDF

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Publication number
CN112803797A
CN112803797A CN202110139072.4A CN202110139072A CN112803797A CN 112803797 A CN112803797 A CN 112803797A CN 202110139072 A CN202110139072 A CN 202110139072A CN 112803797 A CN112803797 A CN 112803797A
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Prior art keywords
bridge arm
valve
branch
auxiliary
series
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CN202110139072.4A
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Chinese (zh)
Inventor
丁骁
张娟娟
王治翔
王蒲瑞
贺冬珊
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Global Energy Interconnection Research Institute
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Global Energy Interconnection Research Institute
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Priority to CN202110139072.4A priority Critical patent/CN112803797A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/145—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/155—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/1552—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a biphase or polyphase arrangement
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/145—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/155—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/162—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/505—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/515—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/521—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Rectifiers (AREA)

Abstract

The invention discloses a hybrid converter topological structure with auxiliary phase commutation at a direct current side and a control method thereof, wherein the topological structure comprises the following components: each phase of bridge arm circuit comprises an upper bridge arm and a lower bridge arm, and thyristor valves are arranged on the upper bridge arm or the lower bridge arm; the first end of the first shutoff valve of the two shutoff valves is connected with the cathode end of the thyristor valve of each phase of upper bridge arm; the first end of the second shutoff valve is connected with the anode end of the thyristor valve of each phase of lower bridge arm; the first ends of the three upper bridge arm auxiliary valves are connected with the second end of the first shutoff valve; the first ends of the three lower bridge arm auxiliary valves are connected with the second end of the second shutoff valve; and the second ends of the three upper bridge arm auxiliary valves and the second ends of the three lower bridge arm auxiliary valves are respectively connected with the output end of the converter transformer. By implementing the method, the occurrence of commutation failure is avoided, and the stability and the safety of the operation of the power grid are ensured.

Description

Hybrid converter topological structure with direct-current side for assisting phase conversion and control method thereof
Technical Field
The invention relates to the technical field of current conversion in power electronics, in particular to a hybrid current converter topological structure with auxiliary phase conversion at a direct current side and a control method thereof.
Background
The traditional power grid phase-change high voltage direct current (LCC-HVDC) power transmission system has the advantages of long-distance large-capacity power transmission, controllable active power and the like, and is widely applied in the world. The converter is used as core equipment of direct current transmission, is a core function unit for realizing alternating current and direct current electric energy conversion, and the operation reliability of the converter determines the operation reliability of an extra-high voltage direct current power grid to a great extent.
Because the traditional converter mostly adopts a thyristor of a semi-controlled device as a core component to form a six-pulse bridge conversion topology, each bridge arm is formed by serially connecting a multi-stage thyristor and a buffer component thereof, and the thyristor does not have self-turn-off capability, phase change failure is easy to occur under the conditions of AC system failure and the like, so that the direct current is increased rapidly, a large amount of direct current transmission power is lost rapidly, and the stable and safe operation of a power grid is influenced.
Disclosure of Invention
In view of this, embodiments of the present invention provide a hybrid converter topology with dc side assisted commutation and a control method thereof, so as to solve the problem that stable operation of a power grid is affected due to a failed commutation.
According to a first aspect, an embodiment of the present invention provides a hybrid converter topology for dc-side assisted phase conversion, where the topology is connected to an ac power grid through a converter transformer, and the topology includes: each phase of 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 arranged on each of the upper bridge arm and the lower bridge arm; the first end of the first shutoff valve is connected with the cathode end of the thyristor valve of each phase of upper bridge arm; the first end of the second shutoff valve is connected with the anode end of the thyristor valve of each phase of lower bridge arm; the first ends of the three upper bridge arm auxiliary valves are connected with the second end of the first shutoff valve; the first ends of the three lower bridge arm auxiliary valves are connected with the second end of the second shutoff valve; the upper bridge arm auxiliary valve and the lower bridge arm auxiliary valve are used for controllably turning off forward current and blocking forward voltage; and the second ends of the three upper bridge arm auxiliary valves and the second ends of the three lower bridge arm auxiliary valves are respectively connected with the output end of the converter transformer.
With reference to the first aspect, in a first embodiment of the first aspect, the shutoff valve, the upper arm assist valve, and the lower arm assist valve are identical in structure.
With reference to the first embodiment of the first aspect, in a second embodiment of the first aspect, the shutoff valve includes: the power supply comprises a first branch circuit, wherein at least one first power device is arranged on the first branch circuit, the at least one first power device is arranged in series, and the first power device is a fully-controlled power electronic device.
With reference to the first embodiment of the first aspect, in a third embodiment of the first aspect, the shutoff valve includes: the second branch circuit is provided with at least one second power device, the at least one second power device is arranged in series, and the second power device is a fully-controlled power electronic device; the third branch circuit has the same structure as the second branch circuit and is arranged in parallel with the second branch circuit; the first buffer component is connected between the second branch and the third branch in parallel; the second branch, the third branch and the first buffer component form an H-bridge structure.
With reference to the first embodiment of the first aspect, in a fourth embodiment of the first aspect, the shutoff valve includes: the fourth branch is provided with a plurality of first diodes which are connected in series; the fifth branch circuit is consistent with the fourth branch circuit in structure and is connected with the fourth branch circuit in parallel; and the sixth branch is connected in parallel between the fourth branch and the fifth branch, a plurality of third power devices connected in series are arranged on the sixth branch, and the third power devices are full-control power electronic devices.
With reference to the first embodiment of the first aspect, in a fifth embodiment of the first aspect, the shutoff valve includes: the seventh branch circuit is provided with at least one fourth power device, the at least one fourth power device is arranged in series, and the fourth power device is a fully-controlled power electronic device; and the eighth branch circuit is connected in parallel with the seventh branch circuit, and is provided with at least one fifth power device and a capacitor element, wherein the at least one fifth power device is connected in series with the capacitor element, the at least one fifth power device is connected in series, and the fifth power device is a fully-controlled power electronic device.
With reference to the first aspect, in a sixth implementation of the first aspect, the thyristor valve includes: a plurality of thyristors; and a plurality of second buffer parts connected in series or in parallel with the plurality of thyristors, respectively.
With reference to the third or sixth embodiment of the first aspect, in a seventh embodiment of the first aspect, the first or second cushioning component includes: the first buffer branch circuit consists of a capacitor; or, a second buffer branch circuit with a resistor and the capacitor connected in series; or, the capacitor and the resistor are connected in parallel by a third buffer branch; or the resistor is connected with the fifth diode in parallel and then connected with the capacitor in series to form a fourth buffer branch circuit; or, the resistor is connected in parallel with the capacitor and then connected in series with the fifth diode to form a fifth buffer branch circuit; or, a sixth buffering branch composed of the lightning arrester; or, a plurality of the first buffering branch, the second buffering branch, the third buffering branch, the fourth buffering branch, the fifth buffering branch and the sixth buffering branch are connected in parallel to form a seventh buffering branch.
According to a second aspect, an embodiment of the present invention provides a method for controlling a dc-side assisted phase-commutated hybrid converter topology, where the method is used for the dc-side assisted phase-commutated hybrid converter topology described in the first aspect or any implementation manner of the first aspect, and the method includes: switching on a shutoff valve corresponding to an ith bridge arm of a hybrid converter topological structure with the direct-current side auxiliary phase conversion, and switching off an upper bridge arm auxiliary valve or a lower bridge arm auxiliary valve corresponding to the ith bridge arm; conducting a thyristor valve of the ith bridge arm; after a control period, returning to the step of conducting the thyristor valve of the ith bridge arm; wherein i ∈ [1,6 ].
With reference to the second aspect, in a first implementation manner of the second aspect, the control method further includes: when detecting that the ith bridge arm has a commutation failure or a short-circuit fault, switching on an upper bridge arm auxiliary valve or a lower bridge arm auxiliary valve connected with the ith bridge arm; triggering a shutoff valve corresponding to the thyristor valve of the ith bridge arm, and carrying out current conversion from the ith bridge arm to an upper bridge arm auxiliary valve or a lower bridge arm auxiliary valve connected with the ith bridge arm; and when the current conversion is finished, switching on a shutoff valve corresponding to the ith bridge arm, and switching off an upper bridge arm auxiliary valve or a lower bridge arm auxiliary valve connected with the ith bridge arm.
The technical scheme of the invention has the following advantages:
1. according to the hybrid converter topological structure with the direct-current side for assisting in phase change and the method thereof, the turn-off valve is arranged on the direct-current side of the hybrid converter, so that bridge arm current can be transferred in advance when the bridge arm fails to change the phase or fails, reverse voltage is provided for the bridge arm, the phase change time area of the thyristor is increased, and reliable turn-off of the thyristor is guaranteed. The transfer of current is realized by using the shutoff valve, so that the upper bridge arm auxiliary valve and the lower bridge arm auxiliary valve participate in phase commutation, the occurrence of phase commutation failure is avoided, and the stability and the safety of the operation of a power grid are further ensured.
2. Each phase bridge arm of the hybrid converter topological structure with the direct-current side for assisting phase conversion provided by the embodiment of the invention respectively comprises an upper bridge arm and a lower bridge arm, the three upper bridge arms share one turn-off valve, the three lower bridge arms share one turn-off valve, the turn-off valves do not need to be connected in series on each bridge arm, the series connection level is less, and the loss of devices is reduced.
3. According to the control method of the hybrid converter topological structure with the auxiliary phase change at the direct current side, provided by the embodiment of the invention, the upper bridge arm auxiliary valve or the lower bridge arm auxiliary valve corresponding to the ith bridge arm is turned off by conducting the turn-off valve corresponding to the ith bridge arm of the hybrid converter topological structure with the auxiliary phase change at the direct current side and the common bus; conducting a thyristor valve of the ith bridge arm; after a control period, returning to the step of conducting the thyristor valve of the ith bridge arm; wherein i ∈ [1,6 ]. Therefore, the hybrid converter topological structure with the auxiliary phase commutation on the direct current side works in a normal phase commutation mode.
4. The embodiment of the invention provides a control method of a hybrid converter topological structure with auxiliary phase change of a DC side common bus, when detecting that the ith bridge arm has failed commutation or short-circuit fault, conducting an upper bridge arm auxiliary valve or a lower bridge arm auxiliary valve connected with the ith bridge arm, triggering a shutoff valve corresponding to the thyristor valve of the ith bridge arm, carrying out commutation of the ith bridge arm to the upper bridge arm auxiliary valve or the lower bridge arm auxiliary valve connected with the ith bridge arm, when the current conversion is finished, the on-off valve corresponding to the ith bridge arm is switched on, the upper bridge arm auxiliary valve or the lower bridge arm auxiliary valve connected with the ith bridge arm is switched off, each phase of bridge arm independently and normally operates, therefore, the upper bridge arm auxiliary valve or the lower bridge arm auxiliary valve is guaranteed to bear the turn-off voltage stress only when the phase change fails or fails, the loss of the device is reduced, and the service life of the device is prolonged.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic diagram of a hybrid converter topology with dc side assisted commutation according to an embodiment of the present invention;
fig. 2 is a block diagram of a thyristor valve according to an embodiment of the invention;
FIG. 3 is a block diagram of a shutoff valve according to an embodiment of the invention;
FIG. 4 is another block diagram of a shutoff valve according to an embodiment of the invention;
FIG. 5 is another block diagram of a shutoff valve according to an embodiment of the invention;
FIG. 6 is another block diagram of a shutoff valve according to an embodiment of the invention;
FIG. 7 is a block diagram of a buffer component according to an embodiment of the invention;
fig. 8 is a control method of a hybrid converter topology with dc-side common bus auxiliary commutation according to an embodiment of the present invention;
fig. 9 is a trigger control timing diagram of a control method of a hybrid converter topology with dc-side common bus auxiliary commutation according to an embodiment of the present invention;
fig. 10 is another trigger control timing diagram of a control method of a hybrid converter topology with dc-side common bus auxiliary commutation according to an embodiment of the present invention;
fig. 11 is a current flow path for a thyristor valve periodic triggering during normal operation according to an embodiment of the present invention;
fig. 12 is a current flow path for thyristor valve turn-off and upper arm assist valve current flow according to an embodiment of the present invention;
fig. 13 is a current flow path of a thyristor valve shut and an upper arm assist valve shut according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The converter is used as core equipment of direct current transmission, is a core function unit for realizing alternating current and direct current electric energy conversion, and the operation reliability of the converter determines the operation reliability of an extra-high voltage direct current power grid to a great extent. However, in the conventional converter, a thyristor which is a half-controlled device is mostly adopted as a core component to form a six-pulse bridge conversion topology, each bridge arm is formed by serially connecting a multi-stage thyristor and a buffer component thereof, and the thyristor does not have self-turn-off capability, so that phase change failure is easy to occur under the conditions of AC system faults and the like, so that the direct current is increased rapidly, a large amount of direct current transmission power is lost rapidly, and the stable and safe operation of a power grid is influenced.
Based on the technical scheme, the invention introduces the turn-off valve at the direct current side, ensures that the thyristor valve has enough reverse recovery time to perform reliable turn-off, and simultaneously utilizes the auxiliary valve branch to assist phase commutation, thereby fundamentally solving the problem of phase commutation failure of the direct current system and ensuring the stable and safe operation of the power grid.
According to an embodiment of the present invention, an embodiment of a hybrid converter topology for dc-side common bus auxiliary commutation is provided, where the hybrid converter topology for dc-side common bus auxiliary commutation is connected to an ac power grid through a converter transformer, as shown in fig. 1, and the hybrid converter topology for dc-side common bus auxiliary commutation includes: the three-phase six-bridge arm circuit comprises a three-phase six-bridge arm circuit, two shutoff valves, three upper bridge arm auxiliary valves and three lower bridge arm auxiliary valves. Each phase of bridge arm circuit of the three-phase six-bridge arm circuit comprises an upper bridge arm and a lower bridge arm, and thyristor valves are arranged on the upper bridge arm or the lower bridge arm. The first end of the first shutoff valve is connected with the cathode end of the thyristor valve of each phase upper bridge arm; the first end of the second shutoff valve is connected with the anode end of the thyristor valve of each phase lower bridge arm. The first ends of the three upper bridge arm auxiliary valves are connected with the second end of the first shutoff valve, the first ends of the three lower bridge arm auxiliary valves are connected with the second end of the second shutoff valve, and the upper bridge arm auxiliary valves and the lower bridge arm auxiliary valves are used for controllable shutoff of forward current and blockage of forward voltage. And the second ends of the three upper bridge arm auxiliary valves and the second ends of the three lower bridge arm auxiliary valves are respectively connected with the output end of the converter transformer.
Specifically, the shutoff valve is used for bidirectional voltage output, can forcedly transfer the current in each bridge arm thyristor valve of the three-phase six-bridge arm circuit to the upper bridge arm auxiliary valve or the lower bridge arm auxiliary valve, and provides reverse recovery voltage for the thyristor valve. As shown in fig. 1, one end of the three-phase six-leg 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 three-phase six-leg circuit includes a V1 valve, a V2 valve, a V3 valve, a V4 valve, a V5 valve, and a V6 valve. The V1 valve, the V3 valve and the V5 valve are upper bridge arms, and each upper bridge arm is provided with a thyristor valve; the V2 valve, the V4 valve and the V6 valve are lower bridge arms, and a thyristor valve is arranged in each lower bridge arm. The V1 valve and the V4 valve are connected in series; the V3 valve and the V6 valve are connected in series; the V2 valve and the V5 valve are connected in series.
Vpa, Vpb and Vpc are upper bridge arm auxiliary valves, first ends of the Vpa, Vpb and Vpc are connected with a second end of a first shutoff valve, and second ends of the Vpa, Vpb and Vpc are respectively connected with an a-phase output end, a b-phase output end and a c-phase output end of the converter transformer; and the Vqa, the Vqb and the Vqc are lower bridge arm auxiliary valves, first ends of the Vqa, the Vqb and the Vqc are connected with a second end of the second shutoff valve, and second ends of the Vqa, the Vqb and the Vqc are respectively connected with an a-phase output end, a b-phase output end and a c-phase output end of the converter transformer.
According to the hybrid converter topological structure with the auxiliary phase change of the direct-current side common bus, the shutoff valve is arranged on the direct-current side of the hybrid converter, so that bridge arm current can be transferred in advance when the bridge arm fails to change the phase or fails, reverse voltage is provided for the bridge arm, the phase change time area of the thyristor is increased, and the thyristor is ensured to be reliably shut down. The transfer of current is realized by using the shutoff valve, so that the upper bridge arm auxiliary valve and the lower bridge arm auxiliary valve participate in phase commutation, the occurrence of phase commutation failure is avoided, and the stability and the safety of the operation of a power grid are further ensured.
Optionally, the thyristor valve comprises at least one thyristor and a second buffer component connected in parallel or in series with the thyristor respectively, wherein the at least one thyristor is arranged in series and the second buffer component is used for the thyristor device to protect against high voltage and large current. As shown in fig. 2, the thyristor valve includes at least one thyristor and second buffer members connected in parallel with the thyristors, respectively.
Alternatively, the structure of the shutoff valve, the upper arm auxiliary valve, and the lower arm auxiliary valve may be the same.
Specifically, as shown in fig. 3, the shut-off valve includes: the power supply device comprises a first branch circuit, wherein at least one first power device is arranged on the first branch circuit, and the at least one first power device is arranged in series. The first 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 and other turn-off devices.
Specifically, as shown in fig. 4, the shut-off valve may include: the second branch, the third branch and the first buffer component form an H-bridge structure.
And at least one second power device is arranged on the second branch and is arranged in series. The second 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 and other turn-off devices. The third branch circuit and the second branch circuit have the same structure and are arranged in parallel with the second branch circuit. And the first buffer component is connected between the second branch and the third branch in parallel, and the second buffer component is used for limiting voltage and current stress.
Specifically, as shown in fig. 5, the shut-off valve may include: a fourth branch, a fifth branch and a sixth branch.
The fourth branch is provided with a plurality of first diodes which are connected in series; the fifth branch and the fourth branch are consistent in structure and are arranged in parallel; the sixth branch is connected in parallel between the fourth branch and the fifth branch. And a plurality of third power devices connected in series are arranged on the sixth branch, the third power devices are full-control power electronic devices, and the full-control power electronic devices are one or more of IGBTs, IGCTs, IEGT, GTOs or MOSFETs.
Specifically, as shown in fig. 6, the shut-off valve may further include: a seventh branch and an eighth branch.
And at least one fourth power device is arranged on the seventh branch and is arranged in series. The fourth power device is a fully-controlled power electronic device, and the fully-controlled power electronic device is one or more of an IGBT, an IGCT, an IEGT, a GTO or a MOSFET. The eighth branch and the seventh branch are arranged in parallel. And the eighth branch circuit is provided with at least one fifth power device and a capacitor element, the at least one fifth power device is connected in series with the capacitor element, the at least one fifth power device is connected in series, the fifth power device is a fully-controlled power electronic device, and the fully-controlled power electronic device is one or more of an IGBT, an IGCT, an IEGT, a GTO or a MOSFET.
Optionally, the first buffer component and the second buffer component are each formed by one or more of a capacitor, a resistance-capacitance loop, a diode, an inductor, or an arrester.
Specifically, as shown in fig. 7, the first buffer part and the second buffer part may be a first buffer branch composed of a capacitor; the second buffer branch can be formed by connecting a resistor and a capacitor in series; the third buffer branch can be formed by connecting a capacitor and a resistor in parallel; the fourth buffer branch RCD1 can be formed by connecting a resistor and a fifth diode in parallel and then connecting the resistor and a capacitor in series; or a fifth buffer branch RCD2 formed by connecting a resistor and a capacitor in parallel and then connecting a fifth diode in series; the lightning arrester can also be a sixth buffering branch circuit consisting of lightning arresters; the buffer circuit can also be a seventh buffer branch formed by connecting a plurality of 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 in parallel.
According to an embodiment of the present invention, there is provided an embodiment of a method for controlling a hybrid converter topology with dc-side assisted commutation, it should be noted that the steps illustrated in the flowchart of the drawings may be executed in a computer system such as a set of computer executable instructions, and although a logical order is illustrated in the flowchart, in some cases, the steps illustrated or described may be executed in an order different from the order illustrated herein.
In this embodiment, a method for controlling a dc-side assisted phase-change hybrid converter topology is provided, which may be used in the above-mentioned dc-side assisted phase-change hybrid converter topology, and fig. 8 is a flowchart according to an embodiment of the present invention, as shown in fig. 8, where the flowchart includes the following steps:
and S21, switching on a turn-off valve corresponding to the ith arm of the hybrid converter topology structure with the direct-current side auxiliary phase conversion, and switching off an upper arm auxiliary valve or a lower arm auxiliary valve corresponding to the ith arm.
And S22, switching on the thyristor valve of the ith bridge arm.
S23, after a control period, returning to the step of conducting the thyristor valve of the ith bridge arm; wherein i ∈ [1,6 ].
Specifically, as shown in fig. 11, the current flow path of the hybrid converter topology under the normal operating condition is shown, the thyristor valve periodically bears voltage and current stress, the upper arm auxiliary valve and the lower arm auxiliary valve are always in the off state, and the thyristor valve of the arm is only stressed when the thyristor valve of the arm is off.
In the control method of the hybrid converter topology with the dc-side auxiliary commutation provided by this embodiment, the upper bridge arm auxiliary valve or the lower bridge arm auxiliary valve corresponding to the ith bridge arm is turned off by turning on the turn-off valve corresponding to the ith bridge arm of the hybrid converter topology with the dc-side common bus auxiliary commutation; conducting a thyristor valve of the ith bridge arm; after a control period, returning to the step of conducting the thyristor valve of the ith bridge arm; wherein i ∈ [1,6 ]. Therefore, the hybrid converter topological structure with the auxiliary phase commutation on the direct current side works in a normal phase commutation mode.
The phase of the V3 valve is changed by using the V1 valve in the hybrid converter shown in fig. 1, Sg1 is a trigger signal of the thyristor valve V1, Sg12 is a trigger signal of the valve Vg1 which can be closed, and Sap is a trigger signal of the upper arm auxiliary valve Vpa.
Fig. 9 is a trigger control timing when a commutation failure or a short-circuit fault occurs. In normal operation, the thyristor valve V11 is periodically triggered, and both the upper arm auxiliary valve Vpa and the shutoff valve Vg1 are in the off state, as shown in fig. 11. t is tfTriggering the upper bridge arm auxiliary valve Vpa to conduct when the valve fails to change phase or has short-circuit fault at the moment V1; at tfThe valve Vg1 which can be shut off is turned off at + Δ t1, and a reverse voltage is output to the bridge arm where the thyristor valve V11 is located, so that commutation of the V11 valve to the upper bridge arm auxiliary valve Vpa is realized, as shown in fig. 12; after the current I11 of the bridge arm where the V11 valve is located crosses zero,v11 turns off and begins to bear the reverse voltage, and the V1 valve current is all transferred to the upper arm assist valve Vpa, as shown in fig. 13; at tfAt time + Δ t2, the upper arm assist valve Vpa starts to close, and the current is completely transferred to the V3 valve, thereby completing the phase change from the V1 valve to the V3 valve. The time from the zero crossing of the current of the bridge arm where the thyristor valve is located to the turning-off of the bridge arm auxiliary valve Vpa is the turning-off time t of the back voltage born by the thyristoroffThe time is controllable, and the reliable turn-off can be ensured only by being longer than the minimum turn-off time of the thyristor. Wherein, Δ t1 is the delay time for turning off the valve which can be turned off, and Δ t2 is the delay time for turning off the upper bridge arm auxiliary valve.
Fig. 10 is a control trigger sequence when a commutation failure or a short-circuit fault is detected in advance, in which the main branch and the auxiliary branch operate alternately in a periodic manner. In each working cycle, the commutation starting time t of the V1 valve and the V3 valve0At time delay t of valve firing pulse Sg1 of V110+ T/3 triggers the upper arm assist valve Vpa at T0The + T/3+ Δ T1 turns off the shutoff valve to apply a reverse voltage to the arm where the V11 valve is located, so that commutation of the V11 valve to the auxiliary arm where the upper arm auxiliary valve Vpa is located is realized, as shown in fig. 12; after the current of the bridge arm where the V11 valve is located crosses zero, the thyristor valve of the bridge arm where the V11 valve is located is turned off and bears reverse voltage, and the current of the V11 valve is completely transferred to the upper bridge arm auxiliary valve Vpa, as shown in fig. 13; after the current of the bridge arm where the V11 valve is positioned is recovered, at t0And the upper bridge arm auxiliary valve Vpa is closed by + T/3+ delta T2, and the current is completely transferred to the V3 valve, so that the phase change is completed. The thyristor valve has controllable reverse bearing time, so that the thyristor valve can be ensured to have enough time to recover blocking capability, and the upper bridge arm auxiliary valve can be controlled to be turned off and bear high pressure, so that the active phase change process can be ensured to be completed smoothly, and the occurrence of phase change failure is avoided. Where Δ T1 is a delay time period for turning off the shutoff valve, Δ T2 is a delay time period for turning off the upper arm assist valve, and T is a control period, for example, T ═ 2 pi.
The embodiment of the present invention provides a method for controlling a hybrid converter topology with dc-side common bus auxiliary phase commutation, when detecting that the ith bridge arm has failed commutation or short-circuit fault, conducting an upper bridge arm auxiliary valve or a lower bridge arm auxiliary valve connected with the ith bridge arm, triggering a shutoff valve corresponding to the thyristor valve of the ith bridge arm, carrying out commutation of the ith bridge arm to the upper bridge arm auxiliary valve or the lower bridge arm auxiliary valve connected with the ith bridge arm, when the current conversion is finished, the on-off valve corresponding to the ith bridge arm is switched on, the upper bridge arm auxiliary valve or the lower bridge arm auxiliary valve connected with the ith bridge arm is switched off, each phase of bridge arm independently and normally operates, therefore, the upper bridge arm auxiliary valve or the lower bridge arm auxiliary valve is guaranteed to bear the turn-off voltage stress only when the phase change fails or fails, the loss of the device is reduced, and the service life of the device is prolonged.
Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims (10)

1. A dc-side assisted commutation hybrid converter topology for accessing an ac grid via a converter transformer, the topology comprising:
each phase of 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 arranged on each of the upper bridge arm and the lower bridge arm;
the first end of the first shutoff valve is connected with the cathode end of the thyristor valve of each phase of upper bridge arm; the first end of the second shutoff valve is connected with the anode end of the thyristor valve of each phase of lower bridge arm;
the first ends of the three upper bridge arm auxiliary valves are connected with the second end of the first shutoff valve;
the first ends of the three lower bridge arm auxiliary valves are connected with the second end of the second shutoff valve; the upper bridge arm auxiliary valve and the lower bridge arm auxiliary valve are used for controllably turning off forward current and blocking forward voltage;
and the second ends of the three upper bridge arm auxiliary valves and the second ends of the three lower bridge arm auxiliary valves are respectively connected with the output end of the converter transformer.
2. The topology of claim 1, wherein the shutoff valves, the upper leg auxiliary valves, and the lower leg auxiliary valves are identical in structure.
3. The topology of claim 2, wherein the shutoff valve comprises:
the power supply comprises a first branch circuit, wherein at least one first power device is arranged on the first branch circuit, the at least one first power device is arranged in series, and the first power device is a fully-controlled power electronic device.
4. The topology of claim 2, wherein the shutoff valve comprises:
the second branch circuit is provided with at least one second power device, the at least one second power device is arranged in series, and the second power device is a fully-controlled power electronic device;
the third branch circuit has the same structure as the second branch circuit and is arranged in parallel with the second branch circuit;
the first buffer component is connected between the second branch and the third branch in parallel;
the second branch, the third branch and the first buffer component form an H-bridge structure.
5. The topology of claim 2, wherein the shutoff valve comprises:
the fourth branch is provided with a plurality of first diodes which are connected in series;
the fifth branch circuit is consistent with the fourth branch circuit in structure and is connected with the fourth branch circuit in parallel;
and the sixth branch is connected in parallel between the fourth branch and the fifth branch, a plurality of third power devices connected in series are arranged on the sixth branch, and the third power devices are full-control power electronic devices.
6. The topology of claim 2, wherein the shutoff valve comprises:
the seventh branch circuit is provided with at least one fourth power device, the at least one fourth power device is arranged in series, and the fourth power device is a fully-controlled power electronic device;
and the eighth branch circuit is connected in parallel with the seventh branch circuit, and is provided with at least one fifth power device and a capacitor element, wherein the at least one fifth power device is connected in series with the capacitor element, the at least one fifth power device is connected in series, and the fifth power device is a fully-controlled power electronic device.
7. The topology of claim 1, wherein the thyristor valve comprises:
a plurality of thyristors;
and a plurality of second buffer parts connected in series or in parallel with the plurality of thyristors, respectively.
8. The topology of claim 4 or 7, wherein the first or second buffer member comprises:
the first buffer branch circuit consists of a capacitor;
or, a second buffer branch circuit with a resistor and the capacitor connected in series;
or, the capacitor and the resistor are connected in parallel by a third buffer branch;
or the resistor is connected with the fifth diode in parallel and then connected with the capacitor in series to form a fourth buffer branch circuit;
or, the resistor is connected in parallel with the capacitor and then connected in series with the fifth diode to form a fifth buffer branch circuit;
or, a sixth buffering branch composed of the lightning arrester;
or, a plurality of the first buffering branch, the second buffering branch, the third buffering branch, the fourth buffering branch, the fifth buffering branch and the sixth buffering branch are connected in parallel to form a seventh buffering branch.
9. A control method of a DC side auxiliary phase-commutated hybrid converter topology according to any one of claims 1 to 8, the method comprising:
switching on a shutoff valve corresponding to an ith bridge arm of a hybrid converter topological structure with the direct-current side auxiliary phase conversion, and switching off an upper bridge arm auxiliary valve or a lower bridge arm auxiliary valve corresponding to the ith bridge arm;
conducting a thyristor valve of the ith bridge arm;
after a control period, returning to the step of conducting the thyristor valve of the ith bridge arm; wherein i ∈ [1,6 ].
10. The method of claim 9, wherein the selection unit includes three two-way valves, the control method further comprising:
when detecting that the ith bridge arm has a commutation failure or a short-circuit fault, switching on an upper bridge arm auxiliary valve or a lower bridge arm auxiliary valve connected with the ith bridge arm;
triggering a shutoff valve corresponding to the thyristor valve of the ith bridge arm, and carrying out current conversion from the ith bridge arm to an upper bridge arm auxiliary valve or a lower bridge arm auxiliary valve connected with the ith bridge arm;
and when the current conversion is finished, switching on a shutoff valve corresponding to the ith bridge arm, and switching off an upper bridge arm auxiliary valve or a lower bridge arm auxiliary valve connected with the ith bridge arm.
CN202110139072.4A 2021-02-01 2021-02-01 Hybrid converter topological structure with direct-current side for assisting phase conversion and control method thereof Pending CN112803797A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114019272A (en) * 2021-10-18 2022-02-08 清华大学 Current converter test circuit and test method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114019272A (en) * 2021-10-18 2022-02-08 清华大学 Current converter test circuit and test method

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