CN214380680U - Hybrid converter topology structure with active phase change unit and forced phase change - Google Patents
Hybrid converter topology structure with active phase change unit and forced phase change Download PDFInfo
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- CN214380680U CN214380680U CN202120287095.5U CN202120287095U CN214380680U CN 214380680 U CN214380680 U CN 214380680U CN 202120287095 U CN202120287095 U CN 202120287095U CN 214380680 U CN214380680 U CN 214380680U
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Abstract
The utility model discloses a hybrid transverter topological structure of initiative commutation unit and forced commutation, wherein, initiative commutation unit sets up in the bridge arm circuit of transverter, and converter transformer's output is connected to its one end, and direct current generating line is connected to the other end, include: the main branch is provided with a thyristor valve and a first control valve, and the first control valve at least has the function of unidirectional voltage output or unidirectional controllable turn-off; and the auxiliary branch is connected with the main branch in parallel, a second control valve is arranged on the auxiliary branch, and the second control valve has a forward current controllable turn-off function and a forward and reverse voltage blocking function. Through implementing the utility model discloses, avoid commutation failure's emergence, guarantee the stable safe operation of electric wire netting.
Description
Technical Field
The utility model relates to a current conversion technical field among the power electronics, concretely relates to hybrid transverter topological structure of initiative commutation unit and forced commutation.
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.
SUMMERY OF THE UTILITY MODEL
In view of this, the embodiment of the present invention provides a hybrid converter topology structure with active commutation unit and forced commutation to solve the problem that the stable operation of the power grid is affected by the failed commutation.
According to a first aspect, the embodiment of the utility model provides an initiative commutation unit sets up in the bridge arm circuit of transverter, and converter transformer's output is connected to its one end, and direct current bus is connected to the other end, include: the main branch is provided with a thyristor valve and a first control valve, and the first control valve at least has the function of unidirectional voltage output or unidirectional controllable turn-off; and the auxiliary branch circuit is connected with the main branch circuit in parallel, a second control valve is arranged on the auxiliary branch circuit, and the second control valve has a forward current controllable turn-off function and a forward and reverse voltage blocking function.
With reference to the first aspect, in a first embodiment of the first aspect, the second control valve includes: the power supply comprises at least one first power unit, at least one second power unit and a control unit, wherein the at least one first power unit is arranged in series and is used for controllable turn-off of forward current and blocking of forward and reverse voltage; a first buffer member disposed in parallel with the first power unit.
With reference to the first implementation manner of the first aspect, in a second implementation manner of the first aspect, the first power unit includes: the power supply comprises a first branch circuit, a second branch circuit and a third branch circuit, wherein the first branch circuit is provided with a first power device and a first thyristor, and the first power device is connected with the first thyristor in series; the first power device is a power electronic device without a reverse blocking function.
With reference to the first implementation manner of the first aspect, in a third implementation manner of the first aspect, the first power unit includes: the second branch circuit is provided with at least one second power device, and the at least one second power device is arranged in series; the first power device is connected with the first thyristor in series; the first power device is a power electronic device without a reverse blocking function; a third branch in series with the second branch; at least one second thyristor is arranged on the third branch, the at least one second thyristor is arranged in series, and the thyristor has a reverse blocking function.
With reference to the first implementation manner of the first aspect, in a fourth implementation manner of the first aspect, the first power unit includes: the fourth branch is provided with two third power devices and a third thyristor, and the two third power devices are connected in series; the two third power devices are connected in series with the third thyristor; the third power device is a power electronic device without a reverse blocking function.
With reference to the first embodiment of the first aspect, in a fifth embodiment of the first aspect, the first power unit includes: the power supply comprises a fifth branch circuit, at least one fourth power device is arranged on the fifth branch circuit, the at least one fourth power device is arranged in series, and the fourth power device is a power electronic device without a reverse blocking function; the sixth branch is provided with at least one fifth power device and at least one fourth thyristor; the at least one fifth power device and the at least one fourth thyristor are alternately arranged; the fifth power device is a power electronic device with a reverse blocking function.
With reference to the first implementation manner of the first aspect, in a sixth implementation manner of the first aspect, the first power unit includes: the power supply comprises a seventh branch circuit, wherein two sixth power devices, a first diode and a fifth thyristor are arranged on the seventh branch circuit, and the two sixth power devices are connected in series; the two sixth power devices, the first diode and the fifth thyristor are sequentially connected in series; the sixth power device is a power electronic device without a reverse blocking function.
With reference to the first implementation manner of the first aspect, in a seventh implementation manner of the first aspect, the first power unit includes: the eighth branch circuit is provided with at least one seventh power device, the at least one seventh power device is arranged in series, and the seventh power device is a power electronic device without a reverse blocking function; the ninth branch is provided with at least one eighth power device, at least one second diode and at least one sixth thyristor; the at least one eighth power device, the at least one second diode and the at least one sixth thyristor are sequentially arranged in series according to the sequence of the eighth power device, the second diode and the sixth thyristor; the eighth power device is a power electronic device with a reverse blocking function.
With reference to the first implementation manner of the first aspect, in an eighth implementation manner of the first aspect, the first power unit includes: a tenth branch comprising a first sub-branch, a second sub-branch, and a third sub-branch; the first sub-branch, the second sub-branch, the third sub-branch and the first buffer component form an H-bridge structure; the first sub-branch is provided with at least one seventh thyristor, and the at least one seventh thyristor is arranged in series; the seventh thyristor is a unidirectional thyristor or a bidirectional thyristor; the second sub-branch is connected in parallel between the first sub-branch and the third sub-branch, at least one ninth power device is arranged on the second sub-branch, the at least one ninth power device is arranged in series, and the ninth power device is a fully-controlled power electronic device; the third sub-branch has the same structure as the first sub-branch, and the third sub-branch is connected in parallel with the second sub-branch.
With reference to the first aspect, in a ninth implementation manner of the first aspect, the thyristor valve includes: at least one thyristor, the at least one thyristor arranged in series; at least one second snubber block connected in parallel or in series with the at least one thyristor.
With reference to the first aspect, in a tenth embodiment of the first aspect, the first control valve includes: at least one second power cell, the at least one second power cell arranged in series; at least one third damping member connected in parallel with the at least one first power cell.
With reference to the tenth implementation manner of the first aspect, in an eleventh implementation manner of the first aspect, the second power unit includes: the power supply comprises an eleventh branch, wherein a first power device is arranged on the eleventh branch, and the second power device is a fully-controlled power electronic device; and the twelfth branch circuit is connected with the first branch circuit in parallel, the second branch circuit is provided with a first capacitor element and the first power device, and the first power device and the first capacitor element are connected in series.
With reference to the tenth implementation manner of the first aspect, in a twelfth implementation manner of the first aspect, the second power unit includes: a thirteenth branch, on which at least one tenth power device is arranged, the at least one tenth power device being arranged in series; the tenth power device is a fully-controlled power electronic device.
With reference to the first embodiment or the ninth embodiment or the tenth embodiment of the first aspect, in a thirteenth embodiment of the first aspect, the first cushioning member and the second cushioning member each include: 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, the embodiment of the present invention provides a hybrid converter topology structure for forced commutation, the topology structure is connected to an ac power grid through a converter transformer, the topology structure includes a three-phase six-leg circuit, each phase of leg includes an upper leg and a lower leg, and at least one upper leg or one lower leg is provided with an active commutation unit according to the first aspect or any one of the embodiments of the first aspect.
The utility model discloses technical scheme has following advantage:
1. the embodiment of the utility model provides an initiative commutation unit includes parallelly connected main branch road and auxiliary branch road, and the main branch road is provided with thyristor valve and first control valve, and first control valve possesses one-way voltage output or one-way controllable shutoff function at least, has great through-current capacity, bears normal operating current; and the second control valve of the auxiliary branch has forward and reverse voltage blocking capacity. The active commutation unit utilizes the advantages that the thyristor and the first control valve can be turned off and the second control valve can be turned off, two branches are connected in parallel, current transfer is realized through the auxiliary branch, the second control valve bears larger turn-off voltage stress when being used for faults, and the second control valve does not need to bear current stress for a long time, so that the increase of device loss is avoided, and the utilization rate of the second control valve is improved. The auxiliary branch circuit which can provide reverse voltage and has self-turn-off capability is connected in parallel on the basis of the main branch circuit, so that reliable turn-off of the main branch circuit and active phase change of the whole bridge arm are realized. When the active commutation unit normally operates, the auxiliary branch can keep a turn-off state and only needs to bear voltage stress; the auxiliary branch is immediately conducted when the active phase change unit fails in phase change, the second control valve can transfer current to the auxiliary branch and provide reverse voltage for the thyristor valve of the main branch, and the main branch is replaced to complete phase change, so that an auxiliary phase change function is realized in a short time, and the occurrence of phase change failure is avoided.
2. The embodiment of the utility model provides a hybrid transverter topological structure of forced commutation, including six bridge arm circuits of three-phase, every looks bridge arm includes bridge arm and lower bridge arm respectively, is provided with initiative commutation unit on at least one bridge arm or the lower bridge arm. The first control valve of the main branch of the active phase change unit can turn off the current of the main branch in advance and provide reverse voltage at the same time, so that the phase change voltage-time area of the thyristor valve of the main branch is increased, the reliable turn-off of the thyristor valve is ensured, the problem of phase change failure is avoided, and the stable and safe operation of a power grid is ensured.
3. The embodiment of the utility model provides a hybrid transverter topological structure of forced commutation, including six bridge arm circuits of three-phase, every looks bridge arm includes bridge arm and lower bridge arm respectively, is provided with initiative commutation unit on at least one bridge arm or the lower bridge arm. The second control valve of the auxiliary branch of the active phase change unit can quickly transfer phase change current and flexibly control phase change time. When the phase change fails, the current of the main branch is transferred to the auxiliary branch, the phase change between the two bridge arms is completed through the second control valve, and the recovery time of the converter after the phase change fails is shortened.
4. The embodiment of the utility model provides a hybrid transverter topological structure of forced commutation, including six bridge arm circuits of three-phase, every looks bridge arm includes bridge arm and lower bridge arm respectively, is provided with initiative commutation unit on at least one bridge arm or the lower bridge arm. The hybrid converter topological structure with forced phase change can conduct the auxiliary branch at any time, effectively reduces the loss of the main branch, and can realize low-voltage and low-turn-off angle operation, thereby reducing the reactive power of the inverter side.
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 embodiments or the technical solutions in 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 for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a block diagram of an active commutation cell according to an embodiment of the present invention;
fig. 2 is a block diagram of a thyristor valve according to an embodiment of the present invention;
fig. 3 is a block diagram of a second control valve according to an embodiment of the present invention;
fig. 4 is another block diagram of a second control valve according to an embodiment of the present invention;
fig. 5 is another block diagram of a second control valve according to an embodiment of the present invention;
fig. 6 is another block diagram of a second control valve according to an embodiment of the present invention;
fig. 7 is another block diagram of a second control valve according to an embodiment of the present invention;
fig. 8 is another block diagram of a second control valve according to an embodiment of the present invention;
fig. 9a is another block diagram of a second control valve according to an embodiment of the present invention;
fig. 9b is another block diagram of a second control valve according to an embodiment of the present invention;
fig. 10 is a block diagram of a first control valve according to an embodiment of the present invention;
fig. 11 is another block diagram of the first control valve according to an embodiment of the present invention;
fig. 12 is a block diagram of a buffer member according to an embodiment of the present invention;
fig. 13 is a block diagram of a forced commutated hybrid converter topology according to an embodiment of the present invention;
FIG. 14 is a flow chart of a method of controlling forced commutation according to an embodiment of the present invention;
fig. 15 is a current flow path according to an embodiment of the present invention in a normal operating state;
fig. 16 is a trigger control sequence for a normal operating state according to an embodiment of the present invention;
fig. 17a is a current flow path through which the primary leg commutates to the auxiliary leg in accordance with an embodiment of the present invention;
fig. 17b is a current flow path of the auxiliary branch current flow stage according to an embodiment of the invention;
fig. 17c is a current flow path during the auxiliary branch turn-off phase according to an embodiment of the present invention;
fig. 18 is a trigger control sequence for a commutation failure or short circuit fault according to an embodiment of the present invention;
fig. 19 is a control trigger sequence when a commutation failure or a short-circuit fault is detected in advance 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 embodiments of the present invention will be clearly and completely described below with reference to the accompanying 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. Based on the embodiments in the present invention, all other embodiments obtained by the skilled in the art without creative work belong to 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 this, the utility model discloses technical scheme utilizes the thyristor and has the advantage of the control valve of shutoff ability, through turn-off the control valve in advance in order to guarantee that thyristor valve possesses sufficient turn-off time and resume shutoff ability, realizes the reliable shutoff of transverter, avoids appearing commutation failure and influences the stable safe operation of electric wire netting.
According to the embodiment of the utility model provides an embodiment of initiative commutation unit is provided, this initiative commutation unit sets up in the bridge arm circuit of transverter. One end of the active commutation unit is connected to the output end of the converter transformer, and the other end is connected to the dc bus, as shown in fig. 1, the active commutation unit includes: a main branch and an auxiliary branch. Wherein, a thyristor valve V11 and a first control valve V12 are arranged on the main branch; the auxiliary branch is arranged in parallel with the main branch, and a second control valve V13 is arranged on the auxiliary branch along the direction from the output end of the converter transformer to the direct current bus. The first control valve V12 has a unidirectional voltage output controllable shutoff function, and the second control valve V13 has a forward current controllable shutoff function and a forward and reverse voltage blocking function.
The active phase change unit provided by the embodiment comprises a main branch and an auxiliary branch which are connected in parallel, wherein the main branch is provided with a thyristor valve and a first control valve, and the first control valve at least has a one-way voltage output or one-way controllable turn-off function, has a large through-current capacity and bears normal running current; and the second control valve of the auxiliary branch has forward and reverse voltage blocking capacity. The active commutation unit utilizes the advantages that the thyristor and the first control valve can be turned off and the second control valve can be turned off, two branches are connected in parallel, current transfer is realized through the auxiliary branch, the second control valve bears larger turn-off voltage stress when being used for faults, and the second control valve does not need to bear current stress for a long time, so that the increase of device loss is avoided, and the utilization rate of the second control valve is improved. The auxiliary branch circuit which can provide reverse voltage and has self-turn-off capability is connected in parallel on the basis of the main branch circuit, so that reliable turn-off of the main branch circuit and active phase change of the whole bridge arm are realized. When the active commutation unit normally operates, the auxiliary branch can keep a turn-off state and only needs to bear voltage stress; the auxiliary branch is immediately conducted when the active phase change unit fails in phase change, the second control valve can transfer current to the auxiliary branch and provide reverse voltage for the thyristor valve of the main branch, and the main branch is replaced to complete phase change, so that an auxiliary phase change function is realized in a short time, and the occurrence of phase change failure is avoided.
Optionally, the thyristor valve V11 comprises at least one thyristor 11 and a third buffer component 12 connected in parallel or in series with the thyristor 11, respectively, wherein the at least one thyristor is arranged in series, and the third buffer component 12 is used for thyristor devices to protect against high voltage and large current. As shown in fig. 2, the thyristor valve V11 includes at least one thyristor 11 and a third buffer member 12 connected in parallel with the thyristor 11, respectively.
Optionally, the second control valve V13 includes: at least one first power unit 131 and at least one first buffer member 132. At least one buffer member 132 is disposed in parallel with at least one power unit 131, i.e., the number of buffer members 132 is the same as the number of first power units 131. At least one power cell 131 is arranged in series for controllable turn-off of the forward current and blocking of the forward and reverse voltage.
Specifically, as shown in fig. 3, the first power unit 131 may be a power electronic unit composed of a first branch circuit.
The first branch circuit is provided with a first power device and a first thyristor, and the first power device is connected with the first thyristor in series. The first power device is a power electronic device without a reverse blocking function, and the power electronic device is one or more of turn-off devices such as an IGBT, an IGCT, an IEGT, a GTO or a MOSFET.
Specifically, as shown in fig. 4, the first power unit 131 may be a power electronic unit composed of a second branch and a third branch.
At least one second power device is arranged on the second branch, and the at least one second power device is arranged in series. The second power is a power electronic device without a reverse blocking function, and the power electronic device is one or more of turn-off devices such as an IGBT, an IGCT, an IEGT, a GTO or a MOSFET. The third branch is connected with the second branch in series, at least one second thyristor is arranged on the third branch, and the at least one second thyristor is connected in series. Wherein the second thyristor has a reverse blocking function.
Specifically, as shown in fig. 5, the first power unit 131 may be a power electronic unit composed of a fourth branch circuit.
And the fourth branch is provided with two third power devices and a third thyristor, the two third power devices are arranged in series, and the two third power devices are arranged in series with the third thyristor. The third power device is a power electronic device without a reverse blocking function, and the power electronic device is one or more of turn-off devices such as an IGBT, an IGCT, an IEGT, a GTO or a MOSFET.
Specifically, as shown in fig. 6, the first power unit 131 may be a power electronic unit composed of a fifth branch and a sixth branch.
At least one fourth power device is arranged on the fifth branch, and the at least one fourth power device is arranged in series. The fourth power device is a power electronic device without a reverse blocking function, and the power electronic device is one or more of turn-off devices such as an IGBT, an IGCT, an IEGT, a GTO or a MOSFET. At least one fifth power device and at least one fourth thyristor are arranged on the sixth branch, and the at least one fifth power device and the at least one fourth thyristor are alternately arranged. The fifth power device is a power electronic device with a reverse blocking function, and the power electronic device is one or more of turn-off devices such as an IGBT, an IGCT, an IEGT, a GTO or a MOSFET.
Specifically, as shown in fig. 7, the first power unit 131 may be a power electronic unit composed of a seventh branch.
The seventh branch is provided with two sixth power devices, a first diode and a fifth thyristor, the two sixth power devices are connected in series, and the two sixth power devices, the first diode and the fifth thyristor are connected in series in sequence. The sixth power device is a power electronic device without a reverse blocking function, and the power electronic device is one or more of turn-off devices such as an IGBT, an IGCT, an IEGT, a GTO, or a MOSFET.
Specifically, as shown in fig. 8, the first power unit 131 may be a power electronic unit composed of an eighth branch and a ninth branch.
At least one seventh power device is arranged on the eighth branch, and the at least one seventh power device is arranged in series. The seventh power device is a power electronic device without a reverse blocking function, and the power electronic device is one or more of turn-off devices such as an IGBT, an IGCT, an IEGT, a GTO, or a MOSFET. The ninth branch circuit is provided with at least one eighth power device, at least one second diode and at least one sixth thyristor, and the at least one eighth power device, the at least one second diode and the at least one sixth thyristor are sequentially connected in series according to the sequence of the eighth power device, the second diode and the sixth thyristor. The eighth power device is a power electronic device without a reverse blocking function, and the power electronic device is one or more of turn-off devices such as an IGBT, an IGCT, an IEGT, a GTO, or a MOSFET.
Specifically, as shown in fig. 9a and 9b, the first power unit 131 may be a power electronic unit composed of a tenth branch.
The tenth branch comprises a first sub-branch, a second sub-branch and a third sub-branch, and the first sub-branch, the second sub-branch, the third sub-branch and the first buffer component form an H-bridge structure. At least one seventh thyristor is arranged on the first sub-branch, and the at least one seventh thyristor is arranged in series, wherein the seventh thyristor is a unidirectional thyristor (fig. 9a) or a bidirectional thyristor (fig. 9 b); the second sub-branch is connected in parallel between the first sub-branch and the third sub-branch, at least one ninth power device is arranged on the second sub-branch, and the at least one ninth power device is arranged in series, wherein the ninth power device is a fully-controlled power electronic device, and the power electronic device is one or more of turn-off devices such as an IGBT, an IGCT, an IEGT, a GTO or an MOSFET; the third sub-branch and the first sub-branch have the same structure, and the third sub-branch and the second sub-branch are arranged in parallel.
The second control valve V13 is a high-voltage shutoff valve having forward current controllable shutoff and forward and reverse voltage blocking capabilities, and the present application does not limit the topology of the second control valve V13, and may be any topology having the functions of forward current controllable shutoff and forward and reverse voltage blocking.
Optionally, the first control valve V12 comprises at least one second power cell 121 and at least one third damping member 122, the at least one first power cell 121 being arranged in series, the second damping member being adapted to limit voltage-current stress. At least one third buffer component 122 is connected in parallel with at least one second power unit 121, that is, the number of the third buffer components 122 is the same as that of the second power units. As is known to those skilled in the art, the third damping member 122 is connected in parallel with the second power unit 121, and the third damping member 122 is not shown in each schematic diagram of the first control valve V12.
Specifically, as shown in fig. 10, the second power unit 121 may be a power electronic unit composed of an eleventh branch and a twelfth branch.
The eleventh branch is provided with a tenth power device, the twelfth branch is connected with the eleventh branch in parallel, the twelfth branch is provided with a first capacitor element and a tenth power device, and the tenth power device and the first capacitor element are arranged in series. The tenth power device is a fully-controlled power electronic device, and the fully-controlled power electronic device is one or more of turn-off devices such as an IGBT, an IGCT, an IEGT, a GTO, or a MOSFET.
Specifically, as shown in fig. 11, the second power unit 121 may also be a power electronic unit composed of a thirteenth branch.
And an eleventh power device is arranged on the thirteenth branch, the eleventh 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 an MOSFET.
The topological form of the first power unit may also be a form of matching between a power electronic device without a reverse blocking function and a diode, a form of a multistage series structure may be formed by matching between a single-stage power electronic device without a reverse blocking function, a single-stage diode and a buffer component, a form of combining between a multistage power electronic device without a reverse blocking function and a buffer component and a multistage diode and a buffer component thereof in series, a form of combining between a multistage power electronic device without a reverse blocking function and a buffer component thereof in series, a form of alternately connecting between a multistage power electronic device without a reverse blocking function and a multistage diode in series, or other topological forms may be used, which is not specifically limited herein and can be determined by those skilled in the art according to actual needs.
The first control valve V12 is a low-voltage shutoff valve, has a unidirectional voltage controllable output capability or a unidirectional controllable shutoff function, and is mainly used for shutting off the main branch current and providing a reverse voltage for the main branch current, so as to ensure that the thyristor valve of the main branch has enough shutoff time to perform reliable shutoff. The topological form of the first control valve V12 is not limited in the present application, and may be any topological form that has a one-way voltage-controllable output or a one-way controllable shut-off function.
Optionally, the first buffer component, the second buffer component and the third buffer component are all formed by one or more of a capacitor, a resistance-capacitance loop, a diode, an inductor or an arrester.
Specifically, as shown in fig. 12, the first buffer member, the second buffer member, and the third buffer member 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; a fifth buffer branch RCD2 formed by a resistor and a capacitor connected in parallel and then connected in series with a fifth diode; the sixth buffering branch circuit can also be composed 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 the embodiment of the utility model provides a hybrid transverter topological structure of forced commutation is provided, and this topological structure passes through converter transformer and inserts alternating current electric wire netting. As shown in fig. 13, the hybrid converter topology structure with forced phase commutation includes a three-phase six-leg circuit, each phase leg includes an upper leg and a lower leg, and at least one of the upper leg or the lower leg is provided with the active phase commutation unit according to the above embodiment.
Specifically, the forced commutated hybrid converter topology as depicted in fig. 13 comprises 3 upper legs and 3 lower legs. Each active commutation cell acts as a converter valve, and the hybrid converter topology for forced commutation described with respect to fig. 13, i.e. comprises converter valves V1, V2, V3, V4, V5 and V6. The main branches of the 3 upper arms respectively comprise V11 and V12, V31 and V32, and V51 and V52, and the auxiliary branches of the 3 upper arms respectively comprise V13, V33 and V53. Wherein, V11, V31 and V51 are thyristor valves, V12, V32 and V52 are first control valves, and V13, V33 and V53 are second control valves. The main branches of the 3 lower arms respectively comprise V12 and V22, V41 and V42, and V61 and V62, and the auxiliary branches of the 3 lower arms respectively comprise V23, V43 and V63. Wherein, V21, V41 and V61 are thyristor valves, V22, V42 and V62 are first control valves, and V23, V43 and V63 are second control valves. The on-off and the on-off of the thyristor valve, the first control valve and the second control valve are controlled by a control trigger control system.
The hybrid converter topological structure for forced commutation can provide reverse voltage and an auxiliary branch with self-turn-off capability by being connected in parallel on the basis of a thyristor valve, so that reliable turn-off of a main branch and active commutation of the whole bridge arm are realized. The auxiliary branch is formed by connecting second control valves with bidirectional pressure bearing capacity in series, namely, a shutoff valve is introduced for each bridge arm.
The hybrid converter topology structure for forced phase commutation provided by the embodiment comprises a three-phase six-bridge arm circuit, each phase bridge arm comprises an upper bridge arm and a lower bridge arm, and at least one upper bridge arm or one lower bridge arm is provided with an active phase commutation unit. The first control valve of the main branch of the active phase change unit can turn off the current of the main branch in advance and provide reverse voltage at the same time, so that the phase change voltage-time area of the thyristor valve of the main branch is increased, the reliable turn-off of the thyristor valve is ensured, the problem of phase change failure is avoided, and the stable and safe operation of a power grid is ensured.
In accordance with an embodiment of the present invention, there is provided an embodiment of a forced commutation control method, it should be noted that the steps illustrated in the flowchart of the figure may be performed in a computer system such as a set of computer executable instructions, and that while a logical order is illustrated in the flowchart, in some cases the steps illustrated or described may be performed in an order different than here.
In this embodiment, a forced commutation control method is provided, which can be used in the hybrid converter topology of forced commutation described above, fig. 14 is a flowchart of a forced commutation control method according to an embodiment of the present invention, as shown in fig. 14, the flowchart includes the following steps:
and S21, conducting the thyristor valve and the first control valve of the main branch of the ith bridge arm of the hybrid converter topology.
And S22, conducting a second control valve of the auxiliary branch of the ith bridge arm of the hybrid converter topology.
And S23, turning off the first control valve of the main branch of the ith bridge arm of the hybrid converter topology.
And S24, turning off the second control valve of the auxiliary branch of the ith bridge arm of the hybrid converter topology.
And S25, conducting the thyristor valve and the first control valve of the main branch of the ith bridge arm of the hybrid converter topological structure after a control period, wherein i belongs to [1,6 ].
Specifically, as shown in fig. 15, the valve current flow path of the hybrid converter topology under normal operating conditions is shown, the main branch is subjected to voltage and current stress periodically, the auxiliary branch is always in an off state, and the auxiliary branch is subjected to voltage stress only when the thyristor valve of the main branch is turned off.
In the control method for forced commutation provided by this embodiment, the second control valve of the auxiliary branch of the ith bridge arm of the hybrid converter topology is kept in an off state, and the thyristor valve and the first control valve of the main branch of the ith bridge arm of the hybrid converter topology are turned on. Therefore, the hybrid converter topological structure with forced commutation can work in a normal commutation operation mode, namely, in a temporary commutation operation mode, the auxiliary branch is in a turn-off state in normal operation of the hybrid converter and only bears voltage stress, and the increment of converter loss in long-term operation is reduced.
And when the current transfer is finished, the second control valve of the auxiliary branch of the ith bridge arm of the hybrid converter topology structure is turned off, so that the forced phase change of the hybrid converter is realized. After a control period, returning to the step of conducting the thyristor valve of the main branch of the ith bridge arm of the hybrid converter topological structure, and continuing to independently and normally operate by the main branch, thereby ensuring that the auxiliary branch bears the turn-off voltage stress only when in fault, reducing the loss of the device and further prolonging the service life of the device.
FIG. 16 shows the timing of the firing control of the V12 valve and the V13 valve in the normal operating mode, t0Indicating the initial trigger time.
Fig. 17a, 17b and 17c show that the V1 valve is turned off when the main branch is commutating to the auxiliary branch, and the auxiliary branch starts to bear voltage stress, the process is divided into three stages, fig. 17a shows that the main branch is commutating to the auxiliary branch, the auxiliary branch receives a trigger signal to turn on, and then the auxiliary branch V13 receives a turn-on signal, the main branch V12 valve receives a turn-off signal, transfers the current of the main branch to the auxiliary branch, and applies a reverse voltage to the main branch; FIG. 17b is the auxiliary branch current flow phase, in which the main branch has been completely turned off and the main branch current has been fully diverted to the auxiliary branch; fig. 17c shows the auxiliary branch off phase, in which the V13 valve of the auxiliary branch is turned off when the off signal is received, and the V1 valve is in an off state and is under voltage. The V12 valve is opened before or at the same time that the V11 valve of the main branch is opened in the next control cycle. The above-described operation can be put into operation when a commutation fault is detected or predicted.
Fig. 18 shows the trigger control sequence of the hybrid converter topology for forced commutation in case of commutation failure or ac short circuit fault. At t in FIG. 18fWhen the phase change failure of the V1 valve to the V3 valve is monitored at the moment, the first preset time delta t is passed1The auxiliary branch V13 valve is conducted for a second preset time period delta t2The V12 valve of the main branch is closed, the commutation process of the main branch to the auxiliary branch is executed, and delta t2≥Δt1Is more than or equal to 0. The main branch current I11 is gradually reduced to zero, the auxiliary branch current I12 is gradually increased, and the current passes through a third preset time period delta t3The V13 valve of the auxiliary branch is turned off, and the time from the zero crossing of the I11 of the main branch current to the turning off of the V13 valve is the turning-off time t of the thyristor valveoffHere, toffGreater than the minimum turn-off time of the thyristor valve to ensure that the thyristor valve V11 has sufficient time to turn off. After the auxiliary branch V13 valve is turned off, the auxiliary branch current will commutate to the V3 valve until reaching the direct current I12, so that the phase change from the V1 valve to the V3 valve is completed, the failure fault of phase change is successfully resisted, and then the main branch V12 valve is turned on before or at the same time when the V11 valve of the next control period is turned on. The operation mode is started when the phase commutation failure is predicted to occur or detected to occur, the phase commutation failure can be successfully avoided, the operation mode is exited when the phase commutation process of the converter is recovered to be normal, the auxiliary branch keeps a turn-off state, and the main branch independently and normally operates.
According to the control method for forced commutation provided by the embodiment, when commutation fails or short-circuit faults occur, the hybrid converter topological structure is controlled to start the operation mode of forced commutation, the occurrence of commutation failure is avoided, the operation mode of forced commutation is quitted when the commutation process of the hybrid converter is recovered to be normal, the auxiliary branch is continuously kept in a turn-off state, and the main branch independently and normally operates, so that the auxiliary branch is guaranteed to bear turn-off voltage stress only when the fault occurs, the loss of a device is reduced, and the service life of the device is prolonged.
Fig. 19 shows a control trigger timing when the hybrid converter topology for forced commutation detects a commutation failure or a short-circuit fault in advance, in which the main branch and the auxiliary branch operate alternately periodically. The specific operation process is shown in fig. 17a, 17b and 17 c. At the beginning of the commutation of the V1 valve and the V3 valve, i.e., the V1 valve trigger pulse Sg1 is delayed by 120 °, or in the vicinity of this moment the auxiliary branch V13 valve is triggered and the main branch V12 valve is shut off over a short period of time (e.g., 1s, 5s, etc.), effecting commutation of the main branch to the auxiliary branch. After the main branch current crosses zero, the main branch V11 valve is closed and bears reverse voltage, and the time from the main branch current crossing zero to the auxiliary branch V13 valve closing is the closing time t of the thyristor valveoffAnd t isoffThe minimum turn-off time of the thyristor valve is longer than the minimum turn-off time of the thyristor valve, so that the reliable turn-off of the thyristor valve is guaranteed, the current of the V1 valve is completely transferred to the auxiliary branch, the V13 valve of the auxiliary branch starts to be turned off after delta t, the V1 valve starts to bear forward voltage, and then the V12 valve of the main branch is turned on before the V11 valve of the next working period is turned on. In the operation mode, the main branch and the auxiliary branch in the bridge arm of the hybrid converter topological structure for forced commutation periodically and alternately operate, on the basis of resisting commutation failure, commutation failure does not need to be predicted, and meanwhile the hybrid converter can be in a small turn-off angle operation mode, so that reactive power consumption of the hybrid converter is reduced.
The forced commutation control method provided by this embodiment can not only resist commutation failure, but also does not need to predict commutation failure through the periodic alternate operation of the main branch and the auxiliary branch. Meanwhile, the hybrid converter is ensured to work in a small-cut-off-angle operation mode, and the reactive power consumption of the hybrid converter is reduced.
Although the embodiments of the present invention have been described with reference to 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 (15)
1. An active commutation unit is arranged in a bridge arm circuit of a current converter, one end of the active commutation unit is connected with the output end of a converter transformer, and the other end of the active commutation unit is connected with a direct current bus, and the active commutation unit is characterized by comprising:
the main branch is provided with a thyristor valve and a first control valve, and the first control valve at least has the function of unidirectional voltage output or unidirectional controllable turn-off;
and the auxiliary branch circuit is connected with the main branch circuit in parallel, a second control valve is arranged on the auxiliary branch circuit, and the second control valve has a forward current controllable turn-off function and a forward and reverse voltage blocking function.
2. The active commutation cell of claim 1, wherein the second control valve comprises:
the power supply comprises at least one first power unit, at least one second power unit and a control unit, wherein the at least one first power unit is arranged in series and is used for controllable turn-off of forward current and blocking of forward and reverse voltage;
at least one first buffer member is disposed in parallel with the at least one first power unit, respectively.
3. The active commutation cell of claim 2, wherein the first power cell comprises:
the power supply comprises a first branch circuit, a second branch circuit and a third branch circuit, wherein the first branch circuit is provided with a first power device and a first thyristor, and the first power device is connected with the first thyristor in series; the first power device is a power electronic device without a reverse blocking function.
4. The active commutation cell of claim 2, wherein the first power cell comprises:
the second branch circuit is provided with at least one second power device, and the at least one second power device is arranged in series; the second power device is a power electronic device without a reverse blocking function;
a third branch in series with the second branch; at least one second thyristor is arranged on the third branch, the at least one second thyristor is arranged in series, and the second thyristor has a reverse blocking function.
5. The active commutation cell of claim 2, wherein the first power cell comprises:
the fourth branch is provided with two third power devices and a third thyristor, and the two third power devices are connected in series; the two third power devices are connected in series with the third thyristor; the third power device is a power electronic device without a reverse blocking function.
6. The active commutation cell of claim 2, wherein the first power cell comprises:
the power supply comprises a fifth branch circuit, at least one fourth power device is arranged on the fifth branch circuit, the at least one fourth power device is arranged in series, and the fourth power device is a power electronic device without a reverse blocking function;
the sixth branch is provided with at least one fifth power device and at least one fourth thyristor; the at least one fifth power device and the at least one fourth thyristor are alternately arranged; the fifth power device is a power electronic device with a reverse blocking function.
7. The active commutation cell of claim 2, wherein the first power cell comprises:
the power supply comprises a seventh branch circuit, wherein two sixth power devices, a first diode and a fifth thyristor are arranged on the seventh branch circuit, and the two sixth power devices are connected in series; the two sixth power devices, the first diode and the fifth thyristor are sequentially connected in series; the sixth power device is a power electronic device without a reverse blocking function.
8. The active commutation cell of claim 2, wherein the first power cell comprises:
the eighth branch circuit is provided with at least one seventh power device, the at least one seventh power device is arranged in series, and the seventh power device is a power electronic device without a reverse blocking function;
the ninth branch is provided with at least one eighth power device, at least one second diode and at least one sixth thyristor; the at least one eighth power device, the at least one second diode and the at least one sixth thyristor are sequentially arranged in series according to the sequence of the eighth power device, the second diode and the sixth thyristor; the eighth power device is a power electronic device with a reverse blocking function.
9. The active commutation cell of claim 2, wherein the first power cell comprises:
a tenth branch comprising a first sub-branch, a second sub-branch, and a third sub-branch; the first sub-branch, the second sub-branch, the third sub-branch and the first buffer component form an H-bridge structure;
the first sub-branch is provided with at least one seventh thyristor, and the at least one seventh thyristor is arranged in series; the seventh thyristor is a unidirectional thyristor or a bidirectional thyristor;
the second sub-branch is connected in parallel between the first sub-branch and the third sub-branch, at least one ninth power device is arranged on the second sub-branch, the at least one ninth power device is arranged in series, and the ninth power device is a fully-controlled power electronic device;
the third sub-branch has the same structure as the first sub-branch, and the third sub-branch is connected in parallel with the second sub-branch.
10. The active commutation cell of claim 1, wherein the thyristor valve comprises:
at least one thyristor, the at least one thyristor arranged in series;
at least one second snubber block connected in parallel or in series with the at least one thyristor.
11. The active commutation cell of claim 1, wherein the first control valve comprises:
at least one second power cell, the at least one second power cell arranged in series;
at least one third damping member connected in parallel with the at least one second power cell.
12. The active commutation cell of claim 11, wherein the second power cell comprises:
the power supply comprises an eleventh branch, wherein a tenth power device is arranged on the eleventh branch, and the tenth power device is a fully-controlled power electronic device;
and a twelfth branch connected in parallel with the eleventh branch, wherein a first capacitor element and the tenth power device are disposed on the twelfth branch, and the tenth power device and the first capacitor element are connected in series.
13. The active commutation cell of claim 11, wherein the second power cell comprises:
a thirteenth branch, on which at least one eleventh power device is arranged, and the at least one eleventh power device is arranged in series; the eleventh power device is a fully-controlled power electronic device.
14. The active commutation cell of claim 2, 10 or 11, wherein the first, second and third damping members each comprise:
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.
15. A hybrid converter topology for forced commutation, the topology being switched into an ac power grid through a converter transformer, the topology comprising a three-phase six-leg circuit, each leg of the phase comprising an upper leg and a lower leg, respectively, wherein at least one of the upper or lower legs is provided with an active commutation cell according to any one of claims 1 to 14.
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| CN116054605A (en) * | 2023-01-28 | 2023-05-02 | 清华大学 | High-voltage direct current converter and control method |
| CN116054605B (en) * | 2023-01-28 | 2023-08-22 | 清华大学 | High-voltage direct current converter and control method |
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