Turn-off converter voltage-sharing technology

Abstract

The invention discloses a turn-off converter voltage-sharing technology, which comprises a dynamic voltage-sharing circuit, a static voltage-sharing circuit and an active turn-off voltage-sharing branch, the dynamic voltage-sharing circuit, the static voltage-sharing circuit and the active turn-off voltage-sharing branch are respectively connected in parallel with a turn-off tube Q. The active turn-off voltage-sharing circuit comprises a lightning arrester and a thyristor which are connected in series. And the thyristor is switched on when the turn-off converter is actively turned off, and is kept locked under other working conditions, so that the abnormal through-flow condition of the lightning arrester is avoided. According to the invention, the turn-off voltage is limited through the lightning arrester so as to equalize the voltage, and the lightning arrester is effectively protected by using the thyristor, so that the explosion of the lightning arrester caused by the out-of-limit energy when the lightning arrester has a fault is avoided, and the topology provides comprehensive safety guarantee for the turn-off tube Q and the lightning arrester.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics technology, and particularly relates to a commutable converter voltage equalization technology. Background Art

[0002] With the development of power systems, high-voltage direct current (HVDC) transmission technology has been favored due to its advantages in long-distance and large-capacity power transmission. Among them, the traditional line-commutated converter based high voltage direct current (LCC-HVDC) technology has more obvious advantages in this regard. However, in LCC, due to the use of semi-controlled devices such as thyristors, commutation failure problems will occur on the inverter side, and continuous commutation failures will lead to DC blocking, causing fluctuations in grid voltage and power. To solve the problem of commutation failure, Patent 201810720168.8 proposed a new commutable converter topology. The difference between this converter and the traditional line-commutated converter is that each arm of the converter consists of a commutable valve string, and a part (0% - 100%, including 100%) of the thyristors in the traditional converter valve string is replaced by commutable converters, forming a commutable converter-thyristor series structure as shown in Figure 1 and a commutable converter series structure as shown in Figure 2 The commutable converter includes, but is not limited to, insulated gate bipolar transistors (IGBTs), gate turn-off thyristors (GTOs), integrated gate-commutated thyristors (IGCTs), injection enhanced gate transistors (IEGTs), etc. In the existing commutable converter topologies, there is already a method of using parallel discrete arresters to limit the overvoltage during the active turn-off of a single device to achieve voltage equalization. However, the parallel arresters may experience faults such as short circuits or device non-conduction, resulting in a large current passing through them for a long time, posing a significant risk to the safe and reliable operation of the converter. Summary of the Invention

[0003] To solve the above problems, the present invention provides a commutable converter voltage equalization technology to solve the problem that the safety of the arrester cannot be guaranteed during the active turn-off process of the existing commutable converter topologies.

[0004] A highly reliable commutable converter topology, the arm of the commutable converter includes a commutable valve string, the commutable valve string includes a plurality of serially connected commutable tubes Q, the commutable tubes Q are used to perform active turn-off, and the commutable converter topology includes: A dynamic voltage equalization circuit, a static voltage equalization circuit, and an active turn-off voltage equalization branch; Each commutable tube Q is respectively connected in parallel with the dynamic voltage equalization circuit, the static voltage equalization circuit, and the active turn-off voltage equalization branch, wherein the active turn-off voltage equalization circuit includes a series-connected arrester and a thyristor, and the thyristor conducts when the commutable converter performs active turn-off.

[0005] According to a specific embodiment of the present invention, the static voltage equalizing circuit includes an equalizing resistor Rp.

[0006] According to a specific embodiment of the present invention, the dynamic voltage equalizing circuit includes a series-connected resistor Rs and capacitor Cs.

[0007] According to a specific embodiment of the present invention, the turn-off thyristor Q is a fully controlled switching device.

[0008] A highly reliable turn-off converter topology, the bridge arm of the turn-off converter includes a turn-off thyristor valve string, the turn-off thyristor valve string includes a plurality of series-connected turn-off thyristors Q, the turn-off thyristor Q is used to perform active turn-off, and the turn-off converter topology includes: A dynamic voltage equalizing circuit, a static voltage equalizing circuit, an active turn-off voltage equalizing branch and a buffer branch; Each turn-off thyristor Q is respectively connected in parallel with the dynamic voltage equalizing circuit, the static voltage equalizing circuit and the active turn-off voltage equalizing branch, wherein the dynamic voltage equalizing circuit includes a series-connected resistor Rs and capacitor Cs, the buffer branch is connected in parallel at both ends of the resistor Rs, the static voltage equalizing circuit includes an equalizing resistor Rp, and the active turn-off voltage equalizing circuit includes a series-connected lightning arrester and thyristor, and the thyristor conducts when the turn-off converter performs active turn-off.

[0009] According to a specific embodiment of the present invention, the buffer branch includes any one of a unidirectional diode D, a series branch of the unidirectional diode D and a resistor R, a rectifier thyristor SCR, a series branch of the rectifier thyristor SCR and a resistor R, and a metal oxide varistor MOV.

[0010] A highly reliable turn-off converter topology, the bridge arm of the turn-off converter includes a turn-off thyristor valve string, the turn-off thyristor valve string includes a plurality of series-connected turn-off thyristors Q, the turn-off thyristor Q is used to perform active turn-off, and the turn-off converter topology includes: A dynamic voltage equalizing circuit, an active turn-off voltage equalizing branch and a buffer branch; Each turn-off thyristor Q is respectively connected in parallel with the dynamic voltage equalizing circuit and the active turn-off voltage equalizing branch, wherein the dynamic voltage equalizing circuit includes a series-connected resistor Rs and capacitor Cs, the buffer branch is connected in parallel at both ends of the resistor Rs, and the active turn-off voltage equalizing circuit includes a series-connected lightning arrester and thyristor, and the thyristor conducts when the turn-off converter performs active turn-off.

[0011] According to a specific embodiment of the present invention, the buffer branch includes a unidirectional diode D or a rectifier thyristor SCR.

[0012] A highly reliable turn-off converter topology, the bridge arm of the turn-off converter includes a turn-off thyristor valve string, the turn-off thyristor valve string includes a plurality of series-connected turn-off thyristors Q, the turn-off thyristor Q is used to perform active turn-off, and the turn-off converter topology includes: Dynamic voltage sharing circuit, static voltage sharing circuit, active turn-off voltage sharing branch and buffer branch; Each turn-off thyristor Q is respectively connected in parallel with the dynamic voltage sharing circuit and the static voltage sharing circuit. The dynamic voltage sharing circuit includes a series-connected resistor Rs and capacitor Cs. The buffer branch is connected in parallel across both ends of the resistor Rs. The static voltage sharing circuit includes a voltage sharing resistor Rp. The active turn-off voltage sharing circuit is connected in parallel across both ends of the turn-off thyristor valve string. Among them, the active turn-off voltage sharing circuit includes a series-connected lightning arrester and thyristor. The thyristor conducts when the turn-off converter actively turns off.

[0013] According to a specific embodiment of the present invention, the buffer branch includes a unidirectional diode D or a rectifier thyristor SCR.

[0014] A highly reliable turn-off converter topology. The arm of the turn-off converter includes a turn-off thyristor valve string. The turn-off thyristor valve string includes a plurality of series-connected turn-off thyristors Q. The turn-off thyristor Q is used to perform active turn-off. The turn-off converter topology includes: Dynamic voltage sharing circuit, active turn-off voltage sharing branch and buffer branch; Each turn-off thyristor Q is respectively connected in parallel with the dynamic voltage sharing circuit. The dynamic voltage sharing circuit includes a series-connected resistor Rs and capacitor Cs. The buffer branch is connected in parallel across both ends of the resistor Rs. The active turn-off voltage sharing circuit is connected in parallel across both ends of the turn-off thyristor Q valve string. The active turn-off voltage sharing circuit includes a series-connected lightning arrester and thyristor. The thyristor conducts when the turn-off converter actively turns off.

[0015] According to a specific embodiment of the present invention, the buffer branch includes a unidirectional diode D or a rectifier thyristor SCR.

[0016] Compared with the prior art, the turn-off converter voltage sharing technology provided by the present invention has the following advantages: 1. During the active turn-off process, by controlling the thyristor to trigger and turn on to connect the lightning arrester MOV, the voltage balance between the series-connected turn-off thyristors Q is achieved.

[0017] 2. During the operation process without active turn-off, the thyristor remains in the off state, and the lightning arrester MOV does not bear voltage and has no aging stress, thereby reducing the probability of aging failure of the lightning arrester MOV and improving the safety and reliability of the device.

[0018] 3. When a problem occurs in the triggering of a single turn-off thyristor Q and an overvoltage protection triggering device is required, the thyristor can withstand the overvoltage value, avoiding the working condition of long-term current flow through the lightning arrester MOV and improving the safety and reliability of the device.

[0019] 4. When the lightning arrester MOV itself fails and is short-circuited, the thyristor fuses so that the branch does not conduct current, which has no impact on normal operation. Even if the thyristor is not blocked, the overvoltage triggering function of the turn-off thyristor Q can be used to protect the device during active turn-off. Brief Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 is a topology diagram of a turn-off converter based on a thyristor valve string and a turn-off valve string according to an embodiment of the present invention.

[0022] Figure 2 is a topology diagram of a turn-off converter based on a turn-off valve string according to an embodiment of the present invention.

[0023] Figure 3 is a topology diagram of a novel turn-off converter arm based on a turn-off valve string according to an embodiment of the present invention.

[0024] Figure 4 is a topology diagram of a first turn-off converter arm according to an embodiment of the present invention.

[0025] Figure 5 is a topology diagram of a second turn-off converter arm according to an embodiment of the present invention.

[0026] Figure 6 is a topology diagram of a third turn-off converter arm according to an embodiment of the present invention.

[0027] Figure 7 is a topology diagram of a fourth turn-off converter arm according to an embodiment of the present invention.

[0028] Figure 8 is a topology diagram of a fifth turn-off converter arm according to an embodiment of the present invention.

[0029] Figure 9 is a topology diagram of a sixth turn-off converter arm according to an embodiment of the present invention.

[0030] Figure 10 is a topology diagram of a seventh turn-off converter arm according to an embodiment of the present invention.

[0031] Figure 11 is a topology diagram of an eighth turn-off converter arm according to an embodiment of the present invention.

[0032] Figure 12 is a topology diagram of a ninth turn-off converter arm according to an embodiment of the present invention.

[0033] Figure 13 It is the topology diagram of the tenth turn-off converter arm according to an embodiment of the present invention. Detailed implementation manners

[0034] In order to enable those skilled in the art to more clearly understand the concepts and ideas of the present invention, the present invention will be described in detail below in conjunction with specific embodiments. It should be understood that the embodiments given herein are only a part of all possible embodiments of the present invention. After reading the specification of this application, those skilled in the art are capable of making improvements, modifications, or substitutions to part or all of the following embodiments, and these improvements, modifications, or substitutions are also included within the scope of protection required by the present invention.

[0035] In this document, terms such as "advance notice", "entry into the station", and other similar terms do not imply any order, quantity, or importance, but are only used to distinguish different elements. In this document, terms such as "one", "a", and other similar terms do not mean that there is only one thing, but mean that the relevant description only refers to one of the things, and the thing may have one or more. In this document, terms such as "include", "comprise", and other similar terms are intended to represent a logical relationship and should not be regarded as representing a spatial structure relationship. For example, "A includes B" is intended to mean that logically B belongs to A, rather than meaning that B is located inside A in terms of space. Additionally, the meanings of terms such as "include", "comprise", and other similar terms should be regarded as open-ended rather than closed-ended. For example, "A includes B" is intended to mean that B belongs to A, but B does not necessarily constitute all of A, and A may also include other elements such as C, D, E, etc.

[0036] In this document, terms such as "embodiment", "the present embodiment", "an embodiment", "one embodiment" do not mean that the relevant description only applies to a specific embodiment, but mean that these descriptions may also apply to one or more other embodiments. Those skilled in the art should understand that in this document, any description made for a certain embodiment can be substituted, combined, or otherwise combined with the relevant descriptions in one or more other embodiments, and the new embodiments generated by substitution, combination, or otherwise combination are easily conceivable by those skilled in the art and fall within the scope of protection of the present invention.

[0037] Embodiment 1 Additional aspects and advantages of the implementation manners of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the implementation manners of the present invention. In combination with Figure 3 and Figure 4, an embodiment of the present invention provides a commutation equalization technique for a turn-off converter. The bridge arm of the turn-off converter includes a turn-off valve string, and the turn-off valve string includes a plurality of serially connected turn-off tubes Q. The turn-off tube Q is used to perform active commutation. The turn-off converter topology includes: A dynamic equalization circuit, a static equalization circuit, and an active commutation equalization branch; Each turn-off tube Q is respectively connected in parallel with the dynamic equalization circuit, the static equalization circuit, and the active commutation equalization branch. The active commutation equalization circuit includes a series-connected lightning arrester and a thyristor. The thyristor is in a locked state during the normal operation of the turn-off converter. When the turn-off converter performs active commutation, the thyristor conducts. Under other conditions, the thyristor is locked. Among them, the turn-off tube Q is a fully controlled switching device, including but not limited to an integrated gate-commutated thyristor (IGCT), an insulated gate bipolar transistor (IGBT), an injection enhanced gate transistor (IEGT), a gate turn-off thyristor (GTO). The static equalization circuit includes an equalization resistor Rp, generally in the order of dozens of kiloohms, to ensure the voltage equalization of the turn-off tube Q under DC bias. The dynamic equalization circuit includes a series-connected resistor Rs and a capacitor Cs. The present invention can limit the overvoltage during the active commutation of a single turn-off tube Q through a shunt discrete lightning arrester to achieve voltage balance. By setting a thyristor in series with the lightning arrester, when the lightning arrester conducts current, it is locked, thereby avoiding faults such as short circuits of the lightning arrester and bringing safety guarantee to the reliable operation of the converter.

[0038] The working principle of this turn-off converter topology is described as follows: During normal operation of the converter, there is no need for active turn-off, and the turn-off thyristor Q remains in the blocked state for a long time. At this time, the turn-off thyristor Q only needs to withstand the voltage and does not need to be triggered to turn on. When the converter needs to perform active turn-off, the control system sends an active turn-off command to the turn-off thyristor Q, and at the same time sends a turn-on command to the thyristor in series with the arrester MOV. At this time, the arrester MOV plays a voltage-limiting role, thus realizing voltage balance during the active turn-off process. When it is detected that the arrester MOV has current flowing through, the thyristor receives a blocking trigger signal to block the thyristor, thereby avoiding the explosion of the arrester MOV due to excessive energy. During the active turn-off process, by controlling the thyristor to be triggered to turn on and connect the arrester MOV, voltage balance between the series-connected turn-off thyristors Q is achieved. During normal operation of the converter, the thyristor remains in the off state, and the arrester MOV does not bear voltage, so there is no aging stress, thus reducing the probability of aging failure of the arrester MOV and providing the safety and reliability of the device. When there is a problem with the triggering of a single turn-off thyristor Q in the turn-off thyristor Q valve string and an overvoltage protection trigger device is required, the thyristor can withstand the overvoltage value, avoiding long-term current flow through the arrester MOV and providing reliability. When the arrester MOV itself fails and is short-circuited, the thyristor is blocked to make the branch not conduct current, which has no impact on the normal operation of the converter. Even if the thyristor is not blocked, the overvoltage trigger function of the turn-off thyristor Q can be used to protect the device during active turn-off.

[0039] Embodiment 2 Combined with Figures 5 - 9 , the embodiment of the present invention also provides a highly reliable turn-off converter topology. The arm of the turn-off converter includes a turn-off thyristor valve string. The turn-off thyristor valve string includes a plurality of series-connected turn-off thyristors Q. The turn-off thyristor Q is used to perform active turn-off. The turn-off converter topology includes: A dynamic voltage equalizing circuit, a static voltage equalizing circuit, an active turn-off voltage equalizing branch, and a buffer branch; Each turn-off thyristor Q is respectively connected in parallel with a dynamic voltage equalizing circuit, a static voltage equalizing circuit and an active turn-off voltage equalizing branch. The dynamic voltage equalizing circuit includes a series-connected resistor Rs and capacitor Cs, and a buffer branch is connected in parallel across both ends of the resistor Rs. The static voltage equalizing circuit includes a voltage equalizing resistor Rp, generally in the order of dozens of kiloohms, to ensure voltage equalization of the turn-off thyristor Q under DC bias. The active turn-off voltage equalizing circuit includes a series-connected lightning arrester and thyristor. The thyristor is in a locked state during the normal operation of the turn-off converter. When the turn-off converter performs active turn-off, the thyristor conducts. Under other conditions, the thyristor is locked. Among them, the buffer branch includes any one of a unidirectional diode D, a series branch of the unidirectional diode D and a resistor R, a rectifier SCR, a series branch of the rectifier SCR and a resistor R, and a metal oxide varistor MOV. The present invention can limit the overvoltage during the active turn-off of a single turn-off thyristor Q through a parallel discrete lightning arrester to achieve voltage balance. By setting a thyristor in series with the lightning arrester, when the lightning arrester conducts current, it is locked, thereby avoiding faults such as short circuits of the lightning arrester and bringing safety guarantee to the reliable operation of the converter.

[0040] Different from the highly reliable turn-off converter topology provided in Embodiment 1, in the embodiment of the present invention, a buffer branch is connected in parallel across both ends of the resistor Rs. The buffer branch conducts when the turn-off thyristor Q turns off, short-circuiting the resistor Rs. By setting the buffer branch, when the turn-off thyristor Q turns off, the conduction of the buffer branch is controlled to short-circuit the resistor Rs, avoiding damage to the turn-off thyristor Q due to excessive voltage across the resistor Rs.

[0041] Embodiment 3 Combined with Figure 10 and Figure 11 Moreover, the embodiment of the present invention also provides a highly reliable turn-off converter topology. The bridge arm of the turn-off converter includes a turn-off thyristor valve string. The turn-off thyristor valve string includes a plurality of series-connected turn-off thyristors Q. The turn-off thyristor Q is used to perform active turn-off. The turn-off converter topology includes: A dynamic voltage equalizing circuit, an active turn-off voltage equalizing branch and a buffer branch; Each turn-off thyristor Q is respectively connected in parallel with the dynamic voltage equalizing circuit and the active turn-off voltage equalizing branch. The dynamic voltage equalizing circuit includes a series-connected resistor Rs and capacitor Cs. The buffer branch is connected in parallel across both ends of the resistor Rs. The active turn-off voltage equalizing circuit includes a series-connected lightning arrester and thyristor. The thyristor is in a locked state during the normal operation of the turn-off converter. When the turn-off converter performs active turn-off, the thyristor conducts. Under other conditions, the thyristor is locked. Among them, the buffer branch includes a unidirectional diode D or a rectifier SCR. The buffer branch conducts when the turn-off thyristor Q turns off, short-circuiting the resistor Rs. By setting the buffer branch, when the turn-off thyristor Q turns off, the conduction of the buffer branch is controlled to short-circuit the resistor Rs, avoiding damage to the turn-off thyristor Q due to excessive voltage across the resistor Rs.

[0042] Different from the highly reliable turn-off converter topology provided in Embodiment 2, the embodiment of the present invention does not include a static voltage equalization circuit, and other structures are the same as the turn-off converter topology provided in Embodiment 1. The present invention can limit the overvoltage during the active turn-off of a single turn-off device Q through a shunt discrete lightning arrester to achieve voltage balance. By setting a thyristor in series with the lightning arrester, when the lightning arrester conducts current, it is blocked, thereby avoiding faults such as short circuits of the lightning arrester and bringing safety guarantees to the reliable operation of the converter.

[0043] Embodiment 4 Combined with Figure 12 , the embodiment of the present invention also provides a highly reliable turn-off converter topology. The arm of the turn-off converter includes a turn-off device valve string. The turn-off device valve string includes a plurality of series-connected turn-off devices Q. The turn-off device Q is used to perform active turn-off. The turn-off converter topology includes: A dynamic voltage equalization circuit, a static voltage equalization circuit, an active turn-off voltage equalization branch, and a buffer branch; Each turn-off device Q is respectively connected in parallel with the dynamic voltage equalization circuit and the static voltage equalization circuit. The dynamic voltage equalization circuit includes a series-connected resistor Rs and a capacitor Cs. The buffer branch is connected in parallel across both ends of the resistor Rs. The static voltage equalization circuit includes a voltage equalization resistor Rp, generally in the order of dozens of kiloohms, to ensure the voltage balance of the turn-off device Q under DC bias. The active turn-off voltage equalization circuit is connected in parallel across both ends of the turn-off device Q valve string. Among them, the active turn-off voltage equalization circuit includes a series-connected lightning arrester and a thyristor. The thyristor is in a blocked state during the normal operation of the turn-off converter. When the turn-off converter performs active turn-off, the thyristor conducts. Under other conditions, the thyristor is blocked. Among them, the buffer branch includes a unidirectional diode D or a rectifier SCR. The buffer branch conducts when the turn-off device Q turns off, short-circuits the resistor Rs. By setting the buffer branch, when the turn-off device Q turns off, by controlling the conduction of the buffer branch, the resistor Rs is short-circuited, avoiding the voltage on the resistor Rs being too high and damaging the turn-off device Q.

[0044] Different from the highly reliable turn-off converter topology provided in Embodiment 2, in the embodiment of the present invention, the active turn-off voltage equalization circuit is connected in parallel across both ends of the turn-off device Q valve string. In the embodiment of the present invention, a single lightning arrester is connected in parallel with multiple turn-off devices Q, which can protect multiple turn-off devices Q. During the normal operation of the converter, there is no need for active turn-off, and the turn-off device Q is in a blocked state for a long time. When the converter needs to perform active turn-off, the control system sends an active turn-off instruction to all turn-off devices Q, and at the same time sends an opening instruction to the thyristor in series with the lightning arrester MOV. At this time, the lightning arrester MOV plays a voltage-limiting role, thereby achieving voltage balance during the active turn-off process. When it is detected that the lightning arrester MOV conducts current, the trigger signal of the thyristor is blocked, and then the thyristor is blocked, thereby avoiding the explosion of the lightning arrester MOV due to energy overlimit.

[0045] Embodiment 5 Combined withFigure 13 In addition, an embodiment of the present invention further provides a highly reliable turn-off converter topology. The arm of the turn-off converter includes a turn-off valve string, and the turn-off valve string includes a plurality of series-connected turn-off tubes Q. The turn-off tube Q is used to perform active turn-off. The turn-off converter topology includes: A dynamic voltage equalization circuit, an active turn-off voltage equalization branch, and a buffer branch; Each turn-off tube Q is respectively connected in parallel with the dynamic voltage equalization circuit. The dynamic voltage equalization circuit includes a series-connected resistor Rs and capacitor Cs. The buffer branch is connected in parallel at both ends of the resistor Rs. The active turn-off voltage equalization circuit is connected in parallel at both ends of the turn-off valve string. The active turn-off voltage equalization circuit includes a series-connected arrester and thyristor. The thyristor is in a locked state during the normal operation of the turn-off converter. When the turn-off converter performs active turn-off, the thyristor conducts. Under other conditions, the thyristor is locked. Among them, the buffer branch includes a unidirectional diode D or a rectifier SCR. By setting the buffer branch to conduct when the turn-off tube Q turns off, the resistor Rs is short-circuited. By setting the buffer branch, when the turn-off tube Q turns off, the conduction of the buffer branch is controlled to short-circuit the resistor Rs, avoiding damage to the turn-off tube Q due to excessive voltage on the resistor Rs.

[0046] Different from the highly reliable turn-off converter topology provided in Embodiment 4, the embodiment of the present invention does not include a static voltage equalization circuit, and other structures are the same as those of the turn-off converter topology provided in Embodiment 4. In the embodiment of the present invention, an arrester is connected in parallel with a plurality of turn-off tubes Q, which can protect multiple turn-off tubes Q. During the normal operation of the converter, there is no need for active turn-off, and the turn-off tubes Q are in a locked state for a long time. When the converter needs to perform active turn-off, the control system sends an active turn-off instruction to all turn-off tubes Q, and at the same time sends an opening instruction to the thyristor connected in series with the arrester MOV. At this time, the arrester MOV plays a voltage-limiting role, thereby realizing voltage equalization during the active turn-off process. When it is detected that the arrester MOV has current flow, the trigger signal of the thyristor is locked, and then the thyristor is locked, thereby avoiding explosion of the arrester MOV due to energy over-limit.

[0047] In summary, the turn-off converter voltage equalization technology provided by the present invention has the following advantages: 1. During the active turn-off process, by controlling the thyristor to trigger and turn on to connect the arrester MOV, voltage equalization between the series-connected turn-off tubes Q is realized.

[0048] 2. During the operation process without active turn-off, the thyristor remains in the off state, and the arrester MOV does not bear voltage and has no aging stress, thereby reducing the probability of aging failure of the arrester MOV and improving the safety and reliability of the device.

[0049] 3. When there is a problem with the triggering of a single turn-off device Q, which leads to the need to trigger the device through overvoltage protection, the thyristor can withstand the overvoltage value, avoiding the working condition of the arrester MOV with long-term current conduction and improving the safety and reliability of the device.

[0050] 4. When the arrester MOV itself fails and is short-circuited, the thyristor fuses to prevent current from flowing through this branch, which has no impact on normal operation. Even if the thyristor is not blocked, the overvoltage triggering function of the turn-off device Q can be used to protect the device during active turn-off.

[0051] The concept, principle and idea of the present invention have been described in detail above in combination with specific embodiments (including examples and instances). Those skilled in the art should understand that the embodiments of the present invention are not limited to the several forms given above. After reading the present application document, those skilled in the art can make any possible improvements, substitutions and equivalent forms to the steps, methods, systems and components in the above embodiments. These improvements, substitutions and equivalent forms should be regarded as falling within the scope of the present invention, and the protection scope of the present invention is only subject to the claims.

Claims

1. A highly reliable switchable converter topology, wherein the bridge arm of the switchable converter comprises a switchable valve string, wherein the switchable valve string comprises a plurality of switchable tubes Q connected in series, wherein the switchable tubes Q are used to perform active shutdown, and wherein: The switchable converter topology includes: Dynamic voltage balancing circuit, static voltage balancing circuit and active shut-off voltage balancing branch; Each of the switchable tubes Q is respectively connected in parallel with the dynamic voltage balancing circuit, the static voltage balancing circuit and the actively switched-off voltage balancing branch, wherein the actively switched-off voltage balancing circuit comprises a lightning arrester and a thyristor connected in series, and the thyristor is turned on when the switchable converter is actively switched off.

2. The high-reliability switchable converter topology according to claim 1, characterized in that: The static voltage balancing circuit includes a voltage balancing resistor Rp.

3. The high-reliability switchable converter topology according to claim 2, characterized in that: The dynamic voltage balancing circuit includes a resistor Rs and a capacitor Cs connected in series.

4. The high-reliability switchable converter topology according to claim 3, characterized in that: The turn-off tube Q is a fully controlled switch device.

5. A highly reliable switchable converter topology, wherein the bridge arm of the switchable converter comprises a switchable valve string, wherein the switchable valve string comprises a plurality of switchable tubes Q connected in series, wherein the switchable tubes Q are used to perform active shutdown, and wherein: The switchable converter topology includes: Dynamic voltage balancing circuit, static voltage balancing circuit, active shut-off voltage balancing branch and buffer branch; Each of the switchable tubes Q is respectively connected in parallel with the dynamic voltage balancing circuit, the static voltage balancing circuit and the actively switched-off voltage balancing branch, wherein the dynamic voltage balancing circuit includes a resistor Rs and a capacitor Cs connected in series, the buffer branch is connected in parallel to both ends of the resistor Rs, the static voltage balancing circuit includes a voltage balancing resistor Rp, and the actively switched-off voltage balancing circuit includes a lightning arrester and a thyristor connected in series, and the thyristor is turned on when the switchable converter is actively switched off.

6. The high-reliability switchable converter topology according to claim 5, characterized in that: The buffer branch includes any one of a unidirectional diode D, a series branch of a unidirectional diode D and a resistor R, a rectifier SCR, a series branch of a rectifier SCR and a resistor R, and a lightning arrester MOV.

7. A highly reliable switchable converter topology, wherein the bridge arm of the switchable converter comprises a switchable valve string, wherein the switchable valve string comprises a plurality of switchable tubes Q connected in series, wherein the switchable tubes Q are used to perform active shutdown, and wherein: The switchable converter topology includes: Dynamic voltage balancing circuit, active shut-down of voltage balancing branch and buffer branch; Each of the turnable tubes Q is connected in parallel with the dynamic voltage balancing circuit and the actively turned-off voltage balancing branch, wherein the dynamic voltage balancing circuit includes a resistor Rs and a capacitor Cs connected in series, the buffer branch is connected in parallel to both ends of the resistor Rs, and the actively turned-off voltage balancing circuit includes a lightning arrester and a thyristor connected in series, and the thyristor is turned on when the turnable converter is actively turned off.

8. The high-reliability switchable converter topology according to claim 7, characterized in that: The buffer branch includes a unidirectional diode D or a rectifier SCR.

9. A highly reliable switchable converter topology, wherein the bridge arm of the switchable converter comprises a switchable valve string, wherein the switchable valve string comprises a plurality of switchable tubes Q connected in series, wherein the switchable tubes Q are used to perform active shutdown, and wherein: The switchable converter topology includes: Dynamic voltage balancing circuit, static voltage balancing circuit, active shut-off voltage balancing branch and buffer branch; Each of the switchable tubes Q is respectively connected in parallel with the dynamic voltage balancing circuit and the static voltage balancing circuit, the dynamic voltage balancing circuit includes a resistor Rs and a capacitor Cs connected in series, the buffer branch is connected in parallel to both ends of the resistor Rs, the static voltage balancing circuit includes a voltage balancing resistor Rp, and the actively shut-off voltage balancing circuit is connected in parallel to both ends of the switchable tube valve string, wherein the actively shut-off voltage balancing circuit includes a lightning arrester and a thyristor connected in series, and the thyristor is turned on when the switchable converter is actively shut down.

10. The high-reliability switchable converter topology according to claim 9, characterized in that: The buffer branch includes a unidirectional diode D or a rectifier SCR.

11. A highly reliable switchable converter topology, wherein the bridge arm of the switchable converter comprises a switchable valve string, wherein the switchable valve string comprises a plurality of switchable tubes Q connected in series, wherein the switchable tubes Q are used to perform active shutdown, and wherein: The switchable converter topology includes: Dynamic voltage balancing circuit, active shut-down of voltage balancing branch and buffer branch; Each of the switchable tubes Q is respectively connected in parallel with the dynamic voltage balancing circuit, the dynamic voltage balancing circuit includes a resistor Rs and a capacitor Cs connected in series, the buffer branch is connected in parallel to both ends of the resistor Rs, the active shutdown voltage balancing circuit is connected in parallel to both ends of the switchable tube valve string, the active shutdown voltage balancing circuit includes a lightning arrester and a thyristor connected in series, and the thyristor is turned on when the switchable converter is actively shut down.

12. The high-reliability switchable converter topology according to claim 11, characterized in that: The buffer branch includes a unidirectional diode D or a rectifier SCR.

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