A symmetrical reciprocating transition circuit and voltage regulation method for a converter transformer on-load tap changer

Abstract

The application discloses a converter transformer on-load voltage regulation switch symmetric reciprocating transition circuit and a voltage regulation method, comprising a first main contact, a second main contact, a first vacuum tube, a second vacuum tube, a third vacuum tube, a first conversion switch, a second conversion switch, a first transition resistor and a second transition resistor. Three vacuum tubes, two transition resistors and two conversion switches are adopted in the transition circuit. In the reciprocating switching process of the transition circuit, the second vacuum tube undertakes the task of breaking the load current, and the first vacuum tube and the third vacuum tube take turns to undertake the task of breaking the inter-stage circulating current. The transition circuit can bear the symmetric reciprocating switching time sequence, and the component action time sequence is mirror-symmetric, so that the mechanical complexity of the on-load tap changer can be effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of on-load tap changer technology, and in particular to a symmetrical reciprocating transition circuit and voltage regulation method for an on-load tap changer of a converter transformer. Background Technology

[0002] On-load tap changers are key components inside power transformers. They can operate under transformer excitation or load conditions, changing the effective turns ratio by altering the connections of several taps led out from the transformer windings, thus regulating the output voltage without interrupting the load current. On-load tap changers have a wide range of applications, especially in converter transformers in ultra-high voltage direct current (UHVDC) transmission projects, to ensure the rated firing angle of the converter during normal operation. Early power transformers mostly used on-load tap changers based on high-speed resistance switching, relying on copper-tungsten arc contacts for load switching. These oil-immersed, non-vacuum on-load tap changers involved frequent switching, resulting in relatively severe arc contact burn-out and rapid oil carbonization and contamination, thus increasing the workload of daily maintenance and periodic inspections for power supply departments. Vacuum-type on-load tap changers primarily use vacuum tubes to extinguish the arc, avoiding the carbonization and contamination of the oil caused by arc extinguishing in oil. Due to the short arc breaking time, low arc voltage, low arc energy consumption, and recondensation of contact metal vapors in the vacuum tube, contact burn-out and corrosion can be minimized. Power electronic on-load tap changers replace vacuum tubes with power electronic components to achieve arc-free operation during on-load switching.

[0003] An on-load tap changer consists of a switching switch, a tap selector, and an electric mechanism. The switching switch, with its independent oil chamber, is the key component for on-load switching, and its core is the use of a transition circuit. Vacuum-type on-load tap changers can be classified according to the number of vacuum tubes: single-contact, double-contact, three-contact, and four-contact circuits; according to the number of transition resistors: single-resistor and double-resistor transitions; and according to the number of contact breaks: single-break and double-break, etc. Various combinations of these can form various transition circuits for vacuum-type on-load tap changers. The vacuum tubes in the transition circuit can be single-break vacuum contacts, double-break vacuum contacts, power electronic components, etc. Different transition circuits have different switching sequences to achieve on-load switching voltage regulation, and the switching tasks of each vacuum tube will also differ. The topology of the transition circuit has a significant impact on the reliability of the on-load tap changer switching process, as well as the failure rate and electrical life of the switch.

[0004] In the on-load tap changer transition circuit, there is a main switching vacuum tube that is only responsible for interrupting the load current and an auxiliary vacuum tube that is only responsible for interrupting the interstage circulating current. In actual ultra-high voltage direct current transmission projects, the load current flowing through the on-load tap changer of the converter transformer is about 500-600A, and the interstage circulating current flowing through the transition resistor during the switching process is about 900-1000A. The circulating current interrupted by the auxiliary vacuum tube in a single operation is significantly greater than the load current interrupted by the main switching vacuum tube, resulting in an imbalance in the interruption tasks of the auxiliary and main switching vacuum tubes.

[0005] The existing vacuum on-load tap changer transition circuit has an asymmetrical control timing when switching from winding tap N to winding tap N+1 and from winding tap N+1 to winding tap N. During the mechanical reciprocating motion of the switching core, the cam mechanism needs to lift and change tracks, which increases the complexity of mechanical manufacturing and the failure rate of the switch. Summary of the Invention

[0006] To overcome the problems in the prior art, the present invention aims to provide a symmetrical reciprocating transition circuit and voltage regulation method for a converter transformer on-load tap changer. This transition circuit can carry symmetrical reciprocating timing. In the forward and reverse reciprocating switching process, the mechanical on-load tap changer using the voltage regulation method has a mirror-symmetrical component action sequence, eliminating the need for a mechanical track-changing mechanism and effectively reducing the mechanical complexity of the on-load tap changer.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A symmetrical reciprocating transition circuit for an on-load tap changer of a converter transformer includes a first main contact, a second main contact, a first vacuum tube, a second vacuum tube, a third vacuum tube, a first changeover switch, a second changeover switch, a first transition resistor, and a second transition resistor.

[0009] Specifically, one end of the first main contact and one end of the first vacuum tube are connected to the first winding tap of the transformer voltage regulating winding; one end of the second main contact and one end of the third vacuum tube are connected to the second winding tap of the transformer voltage regulating winding; the other end of the first vacuum tube, one end of the second vacuum tube, and one end of the first transition resistor are connected to the first stationary contact of the first changeover switch; the other end of the third vacuum tube, the other end of the second vacuum tube, and one end of the second transition resistor are connected to the first stationary contact of the second changeover switch; the other end of the first transition resistor is connected to the second stationary contact of the first changeover switch; the other end of the second transition resistor is connected to the second stationary contact of the second changeover switch; the other end of the first main contact, the other end of the second main contact, the moving contact of the first changeover switch, and the moving contact of the second changeover switch are all connected to the neutral point lead-out of the on-load tap changer.

[0010] Furthermore, when the first main contact, the first vacuum tube, and the second vacuum tube are in a conducting state, and the second main contact and the third vacuum tube are in a disconnected state, when the moving contact of the first changeover switch is connected to the second stationary contact, and the moving contact of the second changeover switch is connected to the first stationary contact, the load current flows out from the neutral point lead-out terminal through the first main contact.

[0011] Furthermore, when the second main contact, the second vacuum tube, and the third vacuum tube are in a conducting state, the first main contact and the first vacuum tube are in a disconnected state, the moving contact of the first changeover switch is connected to the first stationary contact, and the moving contact of the second changeover switch is connected to the second stationary contact, the load current flows out from the neutral point lead-out terminal through the second main contact.

[0012] Furthermore, the first vacuum tube, the second vacuum tube, and the third vacuum tube are single-break vacuum tubes, double-break vacuum tubes, or power electronic components with controllable switching functions.

[0013] A voltage regulation method based on the symmetrical reciprocating transient circuit of the on-load tap changer of the converter transformer as described above includes the following steps:

[0014] The first main contact, the first vacuum tube, and the second vacuum tube are all in the conducting state, the second main contact and the third vacuum tube are all in the disconnected state, the moving contact of the first changeover switch is connected to the second stationary contact, and the moving contact of the second changeover switch is connected to the first stationary contact.

[0015] After disconnecting the first main contact, disconnect the second vacuum tube. After the second vacuum tube has completely extinguished its arc, connect the moving contact of the second changeover switch to the second stationary contact.

[0016] After the third vacuum tube is turned on, the first winding tap and the second winding tap are in the bridging position. The first vacuum tube is disconnected. After the first vacuum tube is completely extinguished, the moving contact of the first changeover switch is connected to the first stationary contact.

[0017] After the second vacuum tube is turned on, the second main contact is turned on, and the load current flows out from the neutral point through the second main contact from the second winding tap. The on-load tap switch switches from the first winding tap to the second winding tap.

[0018] Furthermore, when the first winding tap and the second winding tap are in the bridging position, the current I flowing through the first vacuum tube... V1 =I N / 2+I C The current I flowing through the third vacuum tube V3 =I N / 2-I C ;

[0019] Among them, I N I is the load current. C It is an interstage circulation.

[0020] Furthermore, interstage circulation I C =U S / (R1+R2), where U S R1 is the first transition resistor, and R2 is the second transition resistor.

[0021] A voltage regulation method based on the symmetrical reciprocating transient circuit of the on-load tap changer of the converter transformer as described above includes the following steps:

[0022] The second main contact, the second vacuum tube, and the third vacuum tube are in a conductive state, the first main contact and the first vacuum tube are in a disconnected state, the moving contact of the first changeover switch is connected to the first stationary contact, and the moving contact of the second changeover switch is connected to the second stationary contact.

[0023] After disconnecting the second main contact, disconnect the second vacuum tube. After the second vacuum tube has completely extinguished its arc, connect the moving contact of the first changeover switch to the second stationary contact.

[0024] After turning on the first vacuum tube and completely extinguishing the arc of the third vacuum tube, connect the moving contact of the second changeover switch to the first stationary contact.

[0025] After the second vacuum tube is turned on, the first main contact is turned on, and the load current flows out from the neutral point through the first main contact from the first winding tap. The on-load tap switch switches from the second winding tap to the first winding tap.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The transition circuit of this invention employs three vacuum tubes, two transition resistors, and two switching switches. The dual transition resistors effectively limit the interstage circulating current during switching and reduce resistor heating. The auxiliary vacuum tubes used to interrupt the interstage circulating current are configured in a dual manner: the second vacuum tube is responsible for interrupting the load current, while the first and third vacuum tubes take turns interrupting the interstage circulating current, reducing the switching loss of the auxiliary vacuum tubes and balancing the switching capacity among the vacuum tubes. The transition circuit can support symmetrical reciprocating timing.

[0028] The voltage regulation method of the present invention enables the switching sequence of each switching element to be completely mirror-symmetrical during the reciprocating switching process of the transition circuit from the first winding tap N to the second winding tap N+1 and from the second winding tap N+1 to the first winding tap N. Therefore, the reciprocating mechanical structure of the on-load tap changer does not require a track changing mechanism, which can significantly reduce the mechanical complexity of the on-load tap changer and improve the long-term reliability of the on-load tap changer during its service life. Attached Figure Description

[0029] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0030] Figure 1 A circuit diagram of a symmetrical reciprocating transient circuit for an on-load tap changer of a converter transformer according to an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the switching process in which the first main contact is turned on in the symmetrical reciprocating transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of the switching process in which the first main contact is disconnected in the symmetrical reciprocating transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram of the switching process where the second vacuum tube is disconnected in the symmetrical reciprocating transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0034] Figure 5 This is a schematic diagram of the switching process of the second changeover switch in the symmetrical reciprocating transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0035] Figure 6 This is a schematic diagram of the switching process of the third vacuum tube being turned on in the symmetrical reciprocating transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0036] Figure 7 This is a schematic diagram of the switching process in which the first vacuum tube is disconnected in the symmetrical reciprocating transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0037] Figure 8 This is a schematic diagram of the switching process of the first changeover switch in the symmetrical reciprocating transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0038] Figure 9 This is a schematic diagram of the switching process of the second vacuum tube being turned on in the symmetrical reciprocating transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0039] Figure 10 This is a schematic diagram of the switching process in which the second main contact is turned on in the symmetrical reciprocating transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0040] Figure 11 This is a schematic diagram of the on-load tap changer symmetrical reciprocating transition circuit of the converter transformer according to an embodiment of the present invention, during the process of switching the load from winding tap N to winding tap N+1.

[0041] Figure 12This is a schematic diagram of the on-load tap changer symmetrical reciprocating transition circuit of the converter transformer according to an embodiment of the present invention, during the process of switching the load from winding tap N+1 to winding tap N.

[0042] Figure 13 A circuit diagram of a symmetrical reciprocating transient circuit for an on-load tap changer of a converter transformer, wherein the switching element is a power electronic component, according to an embodiment of the present invention.

[0043] Figure 14 This is a circuit diagram of a symmetrical reciprocating transient circuit for an on-load tap changer of a converter transformer, wherein the switching element is a double-break vacuum tube, according to an embodiment of the present invention. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings.

[0045] See Figure 1 The symmetrical reciprocating transition circuit of the on-load tap changer of the converter includes a first main contact MC1, a second main contact MC2, a first vacuum tube V1, a second vacuum tube V2, a third vacuum tube V3, a first changeover switch T1, a second changeover switch T2, a first transition resistor R1, and a second transition resistor R2.

[0046] Wherein, one end of the first main contact MC1 and one end of the first vacuum tube V1 are connected to the first winding tap N of the transformer voltage regulating winding; one end of the second main contact MC2 and one end of the third vacuum tube V3 are connected to the second winding tap N+1 of the transformer voltage regulating winding; the other end of the first vacuum tube V1, one end of the second vacuum tube V2 and one end of the first transition resistor R1 are connected to the first stationary contact 11 of the first changeover switch T1; the other end of the third vacuum tube V3, the other end of the second vacuum tube V2 and one end of the second transition resistor R2 are connected to the first stationary contact 21 of the second changeover switch; the other end of the first transition resistor R1 is connected to the second stationary contact 12 of the first changeover switch T1; the other end of the second transition resistor R2 is connected to the second stationary contact 22 of the second changeover switch T2; the other end of the first main contact MC1, the other end of the second main contact MC2, the moving contact of the first changeover switch T1 and the moving contact of the second changeover switch T2 are all connected to the neutral point lead-out of the on-load tap changer.

[0047] When the first main contact MC1, the first vacuum tube V1, and the second vacuum tube V2 are all in the conducting state, and the second main contact MC2 and the third vacuum tube V3 are all in the open state, the moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its first stationary contact 21, the on-load tap changer transition circuit can allow the load current to flow out from the neutral point lead-out terminal through the first main contact MC1.

[0048] When the second main contact MC2, the second vacuum tube V2, and the third vacuum tube V3 are all in the conducting state, and the first main contact MC1 and the first vacuum tube V1 are all in the open state, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22, the on-load tap changer transition circuit can allow the load current to flow out from the neutral point lead-out terminal through the second main contact MC2.

[0049] The internal switching elements in the on-load tap changer dual-resistor symmetrical reciprocating transition circuit, namely the first vacuum tube V1, the second vacuum tube V2, and the third vacuum tube V3, can be replaced by a single-break vacuum tube with a double-break vacuum tube or a power electronic component with controllable switching function.

[0050] A voltage regulation method for a symmetrical reciprocating transition circuit of an on-load tap changer in a converter transformer is illustrated using a single-break vacuum tube as an example. When the on-load tap changer switches from tap N of the first winding to tap N+1 of the second winding, the voltage regulation method is as follows:

[0051] like Figure 2 As shown, the first main contact MC1 is in the ON state, the second main contact MC2 is in the OFF state, the first vacuum tube V1 and the second vacuum tube V2 are in the ON state, and the third vacuum tube V3 is in the OFF state. The moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its first stationary contact 21. The first winding tap N is turned on, and the load current flows out from the neutral point lead-out terminal through the first main contact MC1.

[0052] like Figure 3 As shown, the first main contact MC1 is disconnected, the second main contact MC2 remains disconnected, the first vacuum tube V1 and the second vacuum tube V2 remain conducting, and the third vacuum tube V3 remains disconnected. The moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its first stationary contact 21. The first winding tap N remains connected, and the load current flows out from the neutral point lead-out through the first vacuum tube V1, the second vacuum tube V2, and the second changeover switch T2.

[0053] like Figure 4 As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, the first vacuum tube V1 remains on, the second vacuum tube V2 is disconnected, generating an arc, the third vacuum tube V3 remains open, the moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its first stationary contact 21. The first winding tap N remains on, and the load current flows out from the neutral point lead-out through the first vacuum tube V1, the first transition resistor R1, and the first changeover switch T1.

[0054] like Figure 5As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, the first vacuum tube V1 remains on, and the second vacuum tube V2 and the third vacuum tube V3 remain off. The moving contact of the first changeover switch T1 is connected to its second stationary contact 12. After the second vacuum tube V2 has completely extinguished its arc, the moving contact of the second changeover switch T2 is connected to its second stationary contact 22. The first winding tap N remains on, and the load current I... N It flows out from the neutral point lead-out terminal through the first vacuum tube V1, the first transition resistor R1, and the first changeover switch T1.

[0055] like Figure 6 As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, the first vacuum tube V1 remains closed, the second vacuum tube V2 remains open, and the third vacuum tube V3 is closed. The moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22. Both the first winding tap N and the second winding tap N+1 are closed, and the load current I... N The current flows out from the neutral point terminal through the first vacuum tube V1, the first transition resistor R1, the first changeover switch T1, and the third vacuum tube V3, the second transition resistor R2, and the second changeover switch T2, respectively; the transition circuit forms a bridge, generating an interstage circulating current I. C The current I flowing through the first vacuum tube V1 V1 =I N / 2+I C The current I flowing through the third vacuum tube V3 V3 =I N / 2-I C ; where I C =U S / (R1+R2), the U S This is the voltage of the on-load tap changer stage.

[0056] like Figure 7 As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, disconnecting the first vacuum tube V1 and generating an arc. The second vacuum tube V2 remains open, and the third vacuum tube V3 remains closed. The moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22. The second winding tap N+1 remains closed, and the load current flows out from the neutral point lead-out through the third vacuum tube V3, the second transition resistor R2, and the second changeover switch T2.

[0057] like Figure 8As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, the first vacuum tube V1 and the second vacuum tube V2 remain open, and the third vacuum tube V3 remains closed. After the first vacuum tube V1 has completely extinguished its arc, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22. The second winding tap N+1 remains open, and the load current flows out from the neutral point lead-out through the third vacuum tube V3, the second transition resistor R2, and the second changeover switch T2.

[0058] like Figure 9 As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, the first vacuum tube V1 remains open, the second vacuum tube V2 is turned on, the third vacuum tube V3 remains on, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22. The second winding tap N+1 remains on, and the load current flows out from the neutral point lead-out through the third vacuum tube V3, the second vacuum tube V2, and the first changeover switch T1.

[0059] like Figure 10 As shown, the first main contact MC1 remains open, while the second main contact MC2 is closed. The first vacuum tube V1 remains open, while the second vacuum tube V2 and the third vacuum tube V3 remain closed. The moving contact of the first changeover switch T1 is connected to its first stationary contact 11, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22. The second winding tap N+1 remains closed, and the load current flows out from the neutral point lead-out through the second main contact MC2.

[0060] When the on-load tap changer switches from the second winding tap N+1 to the first winding tap N, the switching process is a complete mirror image of the switching process when the on-load tap changer switches from the first winding tap N to the second winding tap N+1. The voltage adjustment method is as follows:

[0061] The second main contact MC2 is in the ON state, the first main contact MC1 is in the OFF state, the third vacuum tube V3 and the second vacuum tube V2 are in the ON state, the first vacuum tube V1 is in the OFF state, the moving contact of the second changeover switch T2 is connected to its second stationary contact 22, and the moving contact of the first changeover switch T1 is connected to its first stationary contact 11. The second winding tap N+1 is turned on, and the load current flows out from the neutral point lead-out terminal through the second main contact MC2.

[0062] With the second main contact MC2 disconnected and the first main contact MC1 remaining open, the third vacuum tube V3 and the second vacuum tube V2 remain conducting, while the first vacuum tube V1 remains open. The moving contact of the second changeover switch T2 is connected to its second stationary contact 22, and the moving contact of the first changeover switch T1 is connected to its first stationary contact 11. The second winding tap N+1 remains connected, and the load current flows out from the neutral point lead-out through the third vacuum tube V3, the second vacuum tube V2, and the first changeover switch T1.

[0063] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 remains on, the second vacuum tube V2 is disconnected, generating an arc, the first vacuum tube V1 remains open, the moving contact of the second changeover switch T2 is connected to its second stationary contact 22, and the moving contact of the first changeover switch T1 is connected to its first stationary contact 11. The second winding tap N+1 remains on, and the load current flows out from the neutral point lead-out through the third vacuum tube V3, the second transition resistor R2, and the second changeover switch T2.

[0064] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 remains on, and the second vacuum tube V2 and the first vacuum tube V1 remain open. The moving contact of the second changeover switch T2 is connected to its second stationary contact 22. After the second vacuum tube V2 has completely extinguished its arc, the moving contact of the first changeover switch T1 is connected to its second stationary contact 12. The second winding tap N+1 remains on, and the load current flows out from the neutral point lead-out through the third vacuum tube V3, the second transition resistor R2, and the second changeover switch T2.

[0065] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 remains closed, the second vacuum tube V2 remains open, and the first vacuum tube V1 is closed. The moving contact of the second changeover switch T2 is connected to its second stationary contact 22, and the moving contact of the first changeover switch T1 is connected to its second stationary contact 12. The second winding tap N+1 and the first winding tap N are both closed, and the load current I... N The current flows out from the neutral point terminal through the third vacuum tube V3, the second transition resistor R2, the second changeover switch T2, and the first vacuum tube V1, the first transition resistor R1, and the first changeover switch T1, respectively; the transition circuit forms a bridge, that is, the first winding tap N and the second winding tap N+1 are in the bridged position, generating an interstage circulating current I. C The current I flowing through the third vacuum tube V3 V3 =I N / 2-I C The current I flowing through the first vacuum tube V1 V1 =I N / 2+I C ; where I C =U S / (R1+R2), the U S This is the voltage of the on-load tap changer stage.

[0066] The second main contact MC2 remains open, and the first main contact MC1 remains open, disconnecting the third vacuum tube V3 and generating an arc. The second vacuum tube V2 remains open, and the first vacuum tube V1 remains closed. The moving contact of the second changeover switch T2 is connected to its second stationary contact 22, and the moving contact of the first changeover switch T1 is connected to its second stationary contact 12. The first winding tap N remains closed, and the load current flows out from the neutral point lead-out through the first vacuum tube V1, the first transition resistor R1, and the first changeover switch T1.

[0067] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 and the second vacuum tube V2 remain open, and the first vacuum tube V1 remains closed. After the third vacuum tube V3 has completely extinguished its arc, the moving contact of the second changeover switch T2 is connected to its first stationary contact 21, and the moving contact of the first changeover switch T1 is connected to its second stationary contact 12. The first winding tap N remains open, and the load current flows out from the neutral point lead-out through the first vacuum tube V1, the first transition resistor R1, and the first changeover switch T1.

[0068] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 remains open, the second vacuum tube V2 is turned on, the first vacuum tube V1 remains on, the moving contact of the second changeover switch T2 is connected to its first stationary contact 21, and the moving contact of the first changeover switch T1 is connected to its second stationary contact 12. The first winding tap N remains on, and the load current flows out from the neutral point lead-out through the first vacuum tube V1, the second vacuum tube V2, and the second changeover switch T2.

[0069] The second main contact MC2 remains open, while the first main contact MC1 remains open. The third vacuum tube V3 remains open, while the second vacuum tube V2 and the first vacuum tube V1 remain open. The moving contact of the second changeover switch T2 is connected to its first stationary contact 21, and the moving contact of the first changeover switch T1 is connected to its second stationary contact 12. The first winding tap N remains open, and the load current flows out from the neutral point lead-out through the first main contact MC1.

[0070] When the internal switching elements in the symmetrical reciprocating transition circuit of the converter transformer on-load tap changer are power electronic components with controllable switching functions and double-break vacuum contacts, the operating sequence of the switching elements and the voltage regulation method are the same, and will not be described again.

[0071] When the on-load tap changer switches from tap N of the first winding to tap N+1 of the second winding, the transition circuit switching process is shown in the diagram below. Figure 11 As shown.

[0072] When the on-load tap changer switches from tap N+1 of the second winding to tap N of the first winding, the transition circuit switching process is shown in the diagram below. Figure 12 As shown.

[0073] In embodiments of the present invention, the switching tasks of the on-load tap changer transition circuit using a vacuum tube are shown in the following table:

[0074]

[0075] Among them, I N U is the load current; S R1 and R2 are the interstage voltage of the on-load tap changer; R1 and R2 are the first transition resistor and the second transition resistor, respectively.

[0076] Figure 13 The circuit diagram is shown below for a symmetrical reciprocating transient circuit of an on-load tap changer for a converter transformer, wherein the switching element is a power electronic component, according to an embodiment of the present invention. Figure 13 As shown, only Figure 1 The single-break vacuum tube in the middle is replaced with a power electronic component with controllable on / off switching, and other components are... Figure 1 The components are the same, the timing of their actions is consistent, and their functions and roles are identical. Figure 1 The function and role of the transition circuit shown are the same, and will not be repeated here.

[0077] Figure 14 This is a circuit diagram of a symmetrical reciprocating transient circuit for an on-load tap changer of a converter transformer, wherein the switching element is a double-break vacuum tube, according to an embodiment of the present invention; as follows: Figure 14 As shown, only Figure 1 The single-break vacuum tube in the middle is replaced with a double-break vacuum tube, and other components are the same as those in the middle. Figure 1 The components are the same, the timing of their actions is consistent, and their functions and roles are identical. Figure 1 The function and role of the transition circuit shown are the same, and will not be repeated here.

[0078] The above description is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention, such as adding a disconnecting switch to the existing vacuum tube circuit to play an electrical isolation and protection role, should be covered within the protection scope of the present invention.

[0079] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A symmetrical reciprocating transition circuit for an on-load tap changer of a converter transformer, characterized in that, It includes a first main contact (MC1), a second main contact (MC2), a first vacuum tube (V1), a second vacuum tube (V2), a third vacuum tube (V3), a first changeover switch (T1), a second changeover switch (T2), a first transition resistor (R1), and a second transition resistor (R2); Wherein, one end of the first main contact (MC1) and one end of the first vacuum tube (V1) are connected to the first winding tap (N) of the transformer voltage regulating winding; one end of the second main contact (MC2) and one end of the third vacuum tube (V3) are connected to the second winding tap (N+1) of the transformer voltage regulating winding; the other end of the first vacuum tube (V1), one end of the second vacuum tube (V2) and one end of the first transition resistor (R1) are connected to the first stationary contact (11) of the first changeover switch (T1); the other end of the third vacuum tube (V3) and the other end of the second vacuum tube (V2) are connected to the first stationary contact (11) of the second changeover switch (T1). One end of the first transition resistor (R2) is connected to the first stationary contact (21) of the second changeover switch; the other end of the first transition resistor (R1) is connected to the second stationary contact (12) of the first changeover switch (T1); the other end of the second transition resistor (R2) is connected to the second stationary contact (22) of the second changeover switch (T2); the other end of the first main contact (MC1), the other end of the second main contact (MC2), the moving contact of the first changeover switch (T1), and the moving contact of the second changeover switch (T2) are all connected to the neutral point lead-out of the on-load tap changer. When the first main contact (MC1), the first vacuum tube (V1) and the second vacuum tube (V2) are in the conducting state, the second main contact (MC2) and the third vacuum tube (V3) are in the disconnected state, the moving contact of the first changeover switch (T1) is connected to the second stationary contact (12), and the moving contact of the second changeover switch (T2) is connected to the first stationary contact (21), the load current flows out from the neutral point lead-out terminal through the first main contact (MC1); When the second main contact (MC2), the second vacuum tube (V2) and the third vacuum tube (V3) are in the conducting state, the first main contact (MC1) and the first vacuum tube (V1) are in the disconnected state, the moving contact of the first changeover switch (T1) is connected to the first stationary contact (11), and the moving contact of the second changeover switch (T2) is connected to the second stationary contact (22), the load current flows out from the neutral point lead-out terminal through the second main contact (MC2); During the reciprocating switching, the second vacuum tube (V2) interrupts the load current, while the first vacuum tube (V1) and the third vacuum tube (V3) take turns interrupting the interstage circulating current.

2. The symmetrical reciprocating transition circuit for on-load tap changer of converter transformer according to claim 1, characterized in that, The first vacuum tube (V1), the second vacuum tube (V2), and the third vacuum tube (V3) are single-break vacuum tubes, double-break vacuum tubes, or power electronic components with controllable switching functions.

3. A voltage regulation method based on the symmetrical reciprocating transient circuit of the on-load tap changer of the converter transformer as described in claim 1, characterized in that, Includes the following steps: The first main contact (MC1), the first vacuum tube (V1) and the second vacuum tube (V2) are all in the conducting state, the second main contact (MC2) and the third vacuum tube (V3) are all in the disconnected state, the moving contact of the first changeover switch (T1) is connected to the second stationary contact (12), and the moving contact of the second changeover switch (T2) is connected to the first stationary contact (21). After disconnecting the first main contact (MC1), disconnect the second vacuum tube (V2). After the second vacuum tube (V2) is completely extinguished, connect the moving contact of the second changeover switch (T2) to the second stationary contact (22). After the third vacuum tube (V3) is turned on, the first winding tap (N) and the second winding tap (N+1) are in the bridging position. The first vacuum tube (V1) is disconnected. After the first vacuum tube (V1) is completely extinguished, the moving contact of the first changeover switch (T1) is connected to the first stationary contact (11). After the second vacuum tube (V2) is turned on, the second main contact (MC2) is turned on. The load current flows from the second winding tap (N+1) through the second main contact (MC2) out of the neutral point. The on-load tap changer switches from the first winding tap (N) to the second winding tap (N+1).

4. The voltage regulation method according to claim 3, characterized in that, When the first winding tap (N) and the second winding tap (N+1) are in the bridging position, the current I flowing through the first vacuum tube (V1) is... V1 =I N / 2+I C The current I flowing through the third vacuum tube (V3) V3 =I N / 2-I C ; Among them, I N For load current, I C It is an interstage circulation.

5. The voltage regulation method according to claim 4, characterized in that, Interstage circulation I C =U S / (R1+R2), where U S R1 is the first transition resistor, and R2 is the second transition resistor.

6. A voltage regulation method based on the symmetrical reciprocating transient circuit of the on-load tap changer of the converter transformer as described in claim 1, characterized in that, Includes the following steps: The second main contact (MC2), the second vacuum tube (V2) and the third vacuum tube (V3) are in the conducting state, the first main contact (MC1) and the first vacuum tube (V1) are in the disconnected state, the moving contact of the first changeover switch (T1) is connected to the first stationary contact (11), and the moving contact of the second changeover switch (T2) is connected to the second stationary contact (22). After disconnecting the second main contact (MC2), disconnect the second vacuum tube (V2). After the second vacuum tube (V2) is completely extinguished, connect the moving contact of the first changeover switch (T1) to the second stationary contact (12). After turning on the first vacuum tube (V1), turn off the third vacuum tube (V3). After the third vacuum tube (V3) is completely extinguished, connect the moving contact of the second changeover switch (T2) to the first stationary contact (21). After the second vacuum tube (V2) is turned on, the first main contact (MC1) is turned on. The load current flows from the first winding tap (N) through the first main contact (MC1) out of the neutral point. The on-load tap changer switches from the second winding tap (N+1) to the first winding tap (N).

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