Vacuum load tap changer transition circuit and voltage regulating method

Abstract

The application discloses a kind of vacuum load tap changer transition circuit and voltage regulating method, the circuit includes: containing first main switch and second main switch load tap changer, containing switching switch, first transition branch, second transition branch and third transition branch transition circuit;One end of first main switch is connected with the first winding tap of transformer voltage regulating winding, one end of second main switch is connected with second winding tap, the other end of first main switch, second main switch, the output end of second transition branch is connected with transformer neutral point;First transition branch is parallelly connected with first main switch;Third transition branch is parallelly connected with second main switch;The static contact of switching switch, first moving contact, second moving contact are respectively connected with the first output end of third transition branch, the input end of first transition branch, the input end of second transition branch one to one correspondence;The application can effectively reduce the switching loss of switch element in load tap changer, improve the service life of transition circuit.

Description

Technical Field

[0001] This invention relates to the field of transformer technology, and in particular to a vacuum on-load tap changer transition circuit and voltage regulation method. 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 connecting 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, ensuring the rated firing angle of the converter during normal operation. Vacuum-type on-load tap changers primarily use vacuum tubes to extinguish the arc, avoiding the carbonization and contamination of the oil caused by oil-based arc extinguishing, which is common with traditional copper-tungsten arc contacts. Due to the short arc breaking time, low arc voltage, low arc energy consumption, and recondensation of contact metal vapors in the vacuum tubes, contact burn-off and corrosion are minimized, leading to the widespread use of vacuum-type on-load tap changers.

[0003] The core of an on-load tap changer is the transition circuit, which uses the principle of transition circuits to achieve tap-changing operations. Depending on the number of transition resistors, there are single-resistor, double-resistor, or multi-resistor transitions. Based on experience in UHVDC projects, the interstage circulating current flowing through the transition resistors in the transition circuit during switching is approximately 900–1000A. This interstage circulating current generates significant heat in the transition resistors. The load current flowing through the main vacuum contacts of the on-load tap changer in the converter transformer is approximately 500–600A. Because the circulating current within the transition circuit is significantly greater than the load current, after multiple switching operations, the vacuum contacts of the on-load tap changer and the internal components of its transition circuit are prone to damage, shortening the lifespan of the transition circuit. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a vacuum on-load tap changer transition circuit and voltage regulation method, which can effectively improve the lifespan of the on-load tap changer transition circuit.

[0005] In a first aspect, embodiments of the present invention provide a vacuum on-load tap changer transition circuit, comprising: an on-load tap changer and a transition circuit; the on-load tap changer comprises: a first main switch and a second main switch; the transition circuit comprises: a changeover switch, a first transition branch, a second transition branch and a third transition branch;

[0006] Wherein, one end of the first main switch is used to connect to the first winding tap in the voltage regulating winding of the transformer, one end of the second main switch is used to connect to the second winding tap in the voltage regulating winding of the transformer, and the other ends of the first main switch and the second main switch are used to connect to the neutral point of the transformer; the first transition branch is connected in parallel with the first main switch; the third transition branch is connected in parallel with the second main switch; the stationary contact of the changeover switch is connected to the first output terminal of the third transition branch; the first moving contact of the changeover switch is connected to the input terminal of the first transition branch, the second moving contact of the changeover switch is connected to the input terminal of the second transition branch, and the output terminal of the second transition branch is used to connect to the neutral point of the transformer.

[0007] As an improvement to the above scheme, the first transition branch includes: a first auxiliary switching element and a first transition resistor; one end of the first auxiliary switching element is connected to the input terminal of the first transition branch, the other end of the first auxiliary switching element is connected to one end of the first transition resistor, and the other end of the first transition resistor is connected to the output terminal of the first transition branch; wherein, the input terminal of the first transition branch is used to connect to the first winding tap in the voltage regulating winding of the transformer, and the output terminal of the first transition branch is used to connect to the neutral point of the transformer.

[0008] As an improvement to the above scheme, the second transition branch includes: a second transition resistor; one end of the second transition resistor is connected to the input terminal of the second transition branch, and the other end of the second transition resistor is connected to the output terminal of the second transition branch.

[0009] As an improvement to the above scheme, the third transition branch includes a second auxiliary switching element and a third auxiliary switching element; the input terminal of the second auxiliary switching element is connected to the input terminal of the third transition branch, the output terminal of the second auxiliary switching element and the input terminal of the third auxiliary switching element are connected to the first output terminal of the third transition branch, and the output terminal of the third auxiliary switching element is connected to the second output terminal of the third transition branch; wherein, the input terminal of the third transition branch is used to connect to the second winding tap in the voltage regulating winding of the transformer, and the second output terminal of the third transition branch is used to connect to the neutral point of the transformer.

[0010] Secondly, embodiments of the present invention provide a voltage regulation method for a vacuum on-load tap changer transition circuit, applying the vacuum on-load tap changer transition circuit as described in the first aspect; the voltage regulation method includes:

[0011] The switching of the on-load tap changer between the first winding tap and the second winding tap is controlled by turning the first main switch and the second main switch on and off.

[0012] By switching the first moving contact and the second moving contact in the switching switch on and off, the connection or disconnection between the third transition branch and the first transition branch and the second transition branch can be controlled.

[0013] By switching the first auxiliary switching element, the second auxiliary switching element, and the third auxiliary switching element on and off, the load current in each branch of the vacuum on-load tap changer transition circuit is controlled, so that the load current flows out from the first winding tap or the second winding tap through the first main switch or the second main switch from the neutral point lead-out terminal, thereby adjusting the voltage of each switching element in the transition circuit during the switching process.

[0014] As an improvement to the above solution, the method includes:

[0015] When the first main switch, the third auxiliary switch element, and the first auxiliary switch element are in the on state, the second auxiliary switch element and the second main switch are in the off state, and the first moving contact of the changeover switch is in the on state, the first winding tap is connected, and the load current flows out from the first winding tap through the first main switch from the neutral point lead-out terminal.

[0016] When the first main switch is turned off, the first winding tap remains connected, and the load current flows out from the neutral point lead-out terminal through the changeover switch and the third auxiliary switch element.

[0017] When the third auxiliary switching element is disconnected, the first winding tap remains connected, and the load current flows out from the neutral point lead-out terminal through the changeover switch and the first transition resistor.

[0018] When the first moving contact of the changeover switch is disconnected, the second moving contact of the changeover switch is turned on, the first winding tap remains connected, and the load current flows out from the neutral point lead-out terminal through the first auxiliary switching element and the first transition resistor.

[0019] When the second auxiliary switching element is turned on, the second moving contact of the changeover switch is turned on, and both the first winding tap and the second winding tap are connected. The load current flows out from the neutral point lead-out terminal through the first transition resistor and the second transition resistor.

[0020] When the first auxiliary switching element is disconnected, the second winding tap is connected, and the load current flows out from the neutral point lead-out terminal through the two auxiliary switching elements, the changeover switch, and the second transition resistor.

[0021] When the third auxiliary switching element is turned on, the second winding tap is connected, and the load current flows out from the neutral point lead-out through the second auxiliary switching element and the third auxiliary switching element.

[0022] When the second main switch is turned on, the second winding tap is connected, and the load current flows out from the neutral point lead-out terminal through the second main switch from the second winding tap, completing the switching process of the on-load tap changer from the first winding tap to the second winding tap.

[0023] As an improvement to the above solution, the method includes:

[0024] When the second main switch, the third auxiliary switch element, and the second auxiliary switch element are in the on state, the first auxiliary switch element is in the off state, and the second moving contact of the changeover switch is in the on state, the second winding tap is connected, and the load current flows out from the second winding tap through the second main switch from the neutral point lead-out terminal.

[0025] When the second main switch is turned off, the second winding tap is turned on, and the load current flows out from the neutral point lead-out terminal through the second auxiliary switching element and the second auxiliary switching element.

[0026] When the third auxiliary switching element is disconnected, the second winding tap remains connected, and the load current flows out from the neutral point lead through the second auxiliary switching element, the changeover switch, and the second transition resistor.

[0027] When the first auxiliary switching element is turned on, both the second winding tap and the first winding tap are connected, and the load current flows out from the neutral point lead-out terminal through the first transition resistor and the second transition resistor.

[0028] When the second auxiliary switching element is disconnected, the first winding tap is connected, and the load current flows out from the neutral point lead-out terminal through the first auxiliary switching element and the first transition resistor.

[0029] When the second moving contact of the changeover switch is disconnected, the first moving contact of the changeover switch is turned on, the first winding tap is connected, and the load current flows out from the neutral point lead-out terminal through the first auxiliary switching element and the first transition resistor.

[0030] When the third auxiliary switching element is turned on, the first winding tap is connected, and the load current flows out from the neutral point lead-out terminal through the changeover switch and the third auxiliary switching element.

[0031] When the first main switch is turned on, the first winding tap is connected, and the load current flows out from the neutral point of the first winding tap through the first main switch, completing the switching process of the on-load tap changer from the second winding tap to the first winding tap.

[0032] As an improvement to the above solution, the method includes:

[0033] When the first winding tap is turned on, and the load current flows out from the first winding tap through the first main switch from the neutral point, the voltage of the first auxiliary switching element, the second auxiliary switching element, and the third auxiliary switching element is zero, the current of the first auxiliary switching element and the third auxiliary switching element is zero, and the voltage of the second auxiliary switching element is determined according to the voltage of the vacuum on-load tap changer transition circuit.

[0034] When the first winding tap remains connected, and the load current flows out from the neutral point through the changeover switch and the third auxiliary switch element, the voltage of the first auxiliary switch element and the third auxiliary switch element is zero, and the current of the first auxiliary switch element and the second auxiliary switch element is zero. The voltage of the second auxiliary switch element is determined according to the voltage of the vacuum on-load tap changer transition circuit, and the current of the third auxiliary switch element is determined according to the current of the vacuum on-load tap changer transition circuit.

[0035] As an improvement to the above solution, the method includes:

[0036] When the first winding tap remains connected, and the load current flows out from the neutral point through the changeover switch and the first transition resistor, the voltages of the first auxiliary switching element and the third auxiliary switching element are zero, and the currents of the second auxiliary switching element and the third auxiliary switching element are zero. The voltage of the second auxiliary switching element is determined based on the voltage of the vacuum on-load tap changer transition circuit, and the current of the first auxiliary switching element is determined based on the current of the vacuum on-load tap changer transition circuit.

[0037] When the load current flows out from the neutral point terminal through the first auxiliary switching element and the first transition resistor, the voltage of the first auxiliary switching element and the third auxiliary switching element is zero, and the current of the second auxiliary switching element and the third auxiliary switching element is zero. The voltage of the second auxiliary switching element is determined according to the voltage of the vacuum on-load tap changer transition circuit and the voltage of the first transition resistor, and the current of the first auxiliary switching element is determined according to the current of the vacuum on-load tap changer transition circuit.

[0038] When both the first winding tap and the second winding tap are connected, and the load current flows out from the neutral point lead through the first transition resistor and the second transition resistor, the voltage of the first auxiliary switching element and the second auxiliary switching element is zero, and the current of the third auxiliary switching element is zero. The voltage of the third auxiliary switching element is determined based on the voltage and current of the vacuum on-load tap changer transition circuit and the resistance values ​​of the first transition resistor and the second transition resistor. The current of the first auxiliary switching element and the second auxiliary switching element is determined based on the current of the vacuum on-load tap changer transition circuit and the resistance values ​​of the first transition resistor and the second transition resistor.

[0039] As an improvement to the above solution, the method includes:

[0040] When the second winding tap is turned on, and the load current flows out from the neutral point lead through the two auxiliary switching elements, the changeover switch, and the second transition resistor, the voltage of the second auxiliary switching element is zero, and the current of the first auxiliary switching element and the second auxiliary switching element is zero. The voltage of the first auxiliary switching element is determined based on the voltage and current of the vacuum on-load tap changer transition circuit and the resistance value of the second transition resistor. The voltage of the third auxiliary switching element is determined based on the current of the vacuum on-load tap changer transition circuit and the resistance value of the second transition resistor. The current of the second auxiliary switching element is determined based on the current of the vacuum on-load tap changer transition circuit.

[0041] When the second winding tap is turned on, and the load current flows out from the neutral point lead through the second auxiliary switching element and the third auxiliary switching element, the voltage of the second auxiliary switching element and the third auxiliary switching element is zero, the current of the first auxiliary switching element is zero, the voltage of the first auxiliary switching element is determined according to the voltage of the vacuum on-load tap changer transition circuit, and the current of the second auxiliary switching element and the third auxiliary switching element is determined according to the current of the vacuum on-load tap changer transition circuit.

[0042] When the second winding tap is turned on, and the load current flows out from the second winding tap through the second main switch from the neutral point, the voltage of the second auxiliary switching element and the third auxiliary switching element is zero, and the current of the first auxiliary switching element, the second auxiliary switching element, and the third auxiliary switching element is zero. The voltage of the first auxiliary switching element is determined according to the voltage of the vacuum on-load tap changer transition circuit.

[0043] Compared to existing technologies, the beneficial effects of this invention are as follows: A vacuum on-load tap changer transition circuit includes an on-load tap changer and a transition circuit; the on-load tap changer includes a first main switch and a second main switch; the transition circuit includes a changeover switch, a first transition branch, a second transition branch, and a third transition branch; wherein, one end of the first main switch is used to connect to a first winding tap in the voltage regulating winding of a transformer, one end of the second main switch is used to connect to a second winding tap in the voltage regulating winding of the transformer, and the other ends of the first and second main switches are used to connect to the neutral point of the transformer; the first transition branch is connected in parallel with the first main switch; the third transition branch is connected in parallel with the second main switch; the stationary contact of the changeover switch is connected to the first transition branch; the first transition branch is connected in parallel with the second main switch; the second transition branch is connected in parallel with the third transition branch; the stationary contact of the changeover switch is connected in parallel with the second transition branch. The first output terminal of the three transition branches is connected; the first moving contact of the changeover switch is connected to the input terminal of the first transition branch, the second moving contact of the changeover switch is connected to the input terminal of the second transition branch, and the output terminal of the second transition branch is connected to the neutral point of the transformer; in this embodiment of the invention, the third auxiliary switch element is responsible for interrupting the load current, and the first and second auxiliary switch elements are responsible for interrupting the interstage circulating current superimposed on the load current. By controlling the on / off state of the first main switch, the second main switch, the first auxiliary switch element, the second auxiliary switch element, and the third auxiliary switch element, reciprocating switching can be achieved, which can effectively reduce the switching loss of the switch element (i.e., vacuum contact) in the on-load tap changer and improve the service life of the transition circuit. Attached Figure Description

[0044] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic block diagram of a vacuum on-load tap changer transition circuit provided in an embodiment of the present invention;

[0046] Figure 2 This is a first circuit diagram of the vacuum on-load tap changer transition circuit provided in an embodiment of the present invention;

[0047] Figure 3 This is a flowchart of a voltage regulation method for a vacuum on-load tap changer transition circuit provided in an embodiment of the present invention;

[0048] Figure 4 This is a circuit diagram of the first switching stage of the vacuum on-load tap changer transition circuit from the first winding tap to the second winding tap provided in an embodiment of the present invention.

[0049] Figure 5 This is a circuit diagram of the second switching stage of the vacuum on-load tap changer transition circuit from the first winding tap to the second winding tap provided in an embodiment of the present invention.

[0050] Figure 6 This is a circuit diagram of the third switching stage of the vacuum on-load tap changer transition circuit from the first winding tap to the second winding tap provided in an embodiment of the present invention.

[0051] Figure 7 This is a circuit diagram of the fourth switching stage of the vacuum on-load tap changer transition circuit from the first winding tap to the second winding tap provided in an embodiment of the present invention.

[0052] Figure 8 This is a circuit diagram of the fifth switching stage of the vacuum on-load tap changer transition circuit from the first winding tap to the second winding tap provided in an embodiment of the present invention.

[0053] Figure 9 This is a circuit diagram of the sixth switching stage of the vacuum on-load tap changer transition circuit from the first winding tap to the second winding tap provided in an embodiment of the present invention.

[0054] Figure 10 This is a circuit diagram of the seventh switching stage of the vacuum on-load tap changer transition circuit from the first winding tap to the second winding tap provided in an embodiment of the present invention.

[0055] Figure 11 This is a circuit diagram of the eighth switching stage of the vacuum on-load tap changer transition circuit from the first winding tap to the second winding tap provided in an embodiment of the present invention.

[0056] Figure 12 This is a timing diagram of the transition circuit of the vacuum on-load tap changer from the first winding tap to the second winding tap provided in an embodiment of the present invention.

[0057] Figure 13 This is a timing diagram of the transition circuit of the vacuum on-load tap changer from the second winding tap to the first winding tap provided in an embodiment of the present invention.

[0058] Figure 14 This is a second circuit diagram of the vacuum on-load tap changer transition circuit provided in an embodiment of the present invention;

[0059] Figure 15 This is the third circuit diagram of the vacuum on-load tap changer transition circuit provided in the embodiment of the present invention. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] It is understood that the various numerical designations used in the embodiments of this invention are merely for descriptive convenience and are not intended to limit the scope of this application. The order of the process numbers does not imply the order of execution; the execution order of each process should be determined by its function and internal logic.

[0062] In embodiments of the invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0063] Please see Figure 1 , Figure 1 This is a schematic block diagram of a vacuum on-load tap changer transition circuit provided in an embodiment of the present invention. The vacuum on-load tap changer transition circuit includes: an on-load tap changer and a transition circuit; the on-load tap changer includes: a first main switch MC1 and a second main switch MC2; the transition circuit includes: a changeover switch T, a first transition branch 21, a second transition branch 22 and a third transition branch 23;

[0064] Wherein, one end of the first main switch MC1 is used to connect to the first winding tap (N) in the voltage regulating winding of the transformer, one end of the second main switch MC2 is used to connect to the second winding tap (N+1) in the voltage regulating winding of the transformer, and the other ends of the first main switch MC1 and the second main switch MC2 are used to connect to the neutral point (0) of the transformer; the first transition branch 21 is connected in parallel with the first main switch MC1; the third transition branch 23 is connected in parallel with the second main switch MC2; the stationary contact 10 of the changeover switch T is connected to the first output terminal of the third transition branch 23; the first moving contact 11 of the changeover switch T is connected to the input terminal of the first transition branch 21, the second moving contact 12 of the changeover switch T is connected to the input terminal of the second transition branch 22, and the output terminal of the second transition branch 22 is used to connect to the neutral point (0) of the transformer.

[0065] In this embodiment of the invention, both the first main switch MC1 and the second main switch MC2 are vacuum contacts. They take turns to perform the switching task, which can realize reciprocating switching, reduce the probability of failure, reduce the component loss during the on-load tap changer switching process, and improve the service life of the transition circuit.

[0066] Taking a single-break vacuum contact as an example, in a transition circuit, the switching element uses a switching element with a single break. Figure 2 As shown, the first transition branch 21 includes: a first auxiliary switching element V1 and a first transition resistor R1; one end of the first auxiliary switching element V1 is connected to the input terminal of the first transition branch 21, the other end of the first auxiliary switching element V1 is connected to one end of the first transition resistor R1, and the other end of the first transition resistor R1 is connected to the output terminal of the first transition branch 21; wherein, the input terminal of the first transition branch 21 is used to connect to the first winding tap (N) in the voltage regulating winding of the transformer, and the output terminal of the first transition branch 21 is used to connect to the neutral point (0) of the transformer.

[0067] The second transition branch 22 includes: a second transition resistor R2; one end of the second transition resistor R2 is connected to the input terminal of the second transition branch 22, and the other end of the second transition resistor R2 is connected to the output terminal of the second transition branch 22.

[0068] The third transition branch 23 includes a second auxiliary switching element V2 and a third auxiliary switching element V3; the input terminal of the second auxiliary switching element V2 is connected to the input terminal of the third transition branch 23, the output terminal of the second auxiliary switching element V2 and the input terminal of the third auxiliary switching element V3 are connected to the first output terminal of the third transition branch 23, and the output terminal of the third auxiliary switching element V3 is connected to the second output terminal of the third transition branch 23; wherein, the input terminal of the third transition branch 23 is used to connect to the second winding tap (N+1) in the voltage regulating winding of the transformer, and the second output terminal of the third transition branch 23 is used to connect to the neutral point (0) of the transformer.

[0069] In this embodiment of the invention, the use of two transition resistors (R1, R2) in the transition circuit 2 reduces the heat generation of a single resistor, facilitates design and installation, and ensures insulation distance. Simultaneously, among the switching elements (first auxiliary switching element V1, second auxiliary switching element V2, and third auxiliary switching element V3) within the transition circuit 2, the third auxiliary switching element V3 is responsible for interrupting the load current, while the first and second auxiliary switching elements V1 and V2 are responsible for interrupting the inter-stage circulating current superimposed on the load current. By controlling the on / off states of the first main switch MC1, second main switch MC2, first auxiliary switching element V1, second auxiliary switching element V2, and third auxiliary switching element V3 according to a specific timing sequence, the reciprocating switching of the on-load tap changer can be achieved. The reciprocating switching sequence is reversible, improving the reliability of the on-load tap changer operation, reducing switching losses of the switching elements (i.e., vacuum contacts) in the on-load tap changer, and extending the service life of the transition circuit.

[0070] For the aforementioned vacuum on-load tap changer transition circuit, this embodiment of the invention also provides a voltage regulation method for the vacuum on-load tap changer transition circuit, such as... Figure 3 As shown, the specific voltage regulation methods include:

[0071] S11: By switching the first main switch and the second main switch on and off, the on-load tap changer is controlled to switch between the first winding tap and the second winding tap.

[0072] S12: By switching the first moving contact and the second moving contact in the switching switch on and off, the connection or disconnection between the third transition branch and the first transition branch and the second transition branch is controlled.

[0073] S13: By switching on and off the first auxiliary switching element, the second auxiliary switching element, and the third auxiliary switching element, the load current in each branch of the vacuum on-load tap changer transition circuit is controlled, so that the load current flows out from the first winding tap or the second winding tap through the first main switch or the second main switch from the neutral point lead-out terminal, so as to adjust the voltage of each switching element in the transition circuit during the switching process.

[0074] Taking the switching process of the on-load tap changer from the first winding tap (N) to the second winding tap (N+1) of the transformer's regulating winding as an example, the voltage regulation process of the transition circuit is explained in detail. The transition circuit has a unique division of switching stages, and the electrical stress borne by the switching elements in each stage is different, with a total of eight switching stages.

[0075] First switching stage: When the first main switch MC1, the third auxiliary switch element V3, and the first auxiliary switch element V1 are in the ON state, the second auxiliary switch element V2 and the second main switch MC2 are in the OFF state, and the first moving contact 11 of the changeover switch T is in the ON state (i.e., the stationary contact 10 is connected to the first moving contact 11), the first winding tap (N) is connected, and the load current flows from the first winding tap (N) through the first main switch MC1 from the neutral point (O) lead-out terminal, such as... Figure 4 As shown.

[0076] In this circuit, the power supply side can be equivalent to a voltage source and a current source, which have a certain phase difference, as expressed by the following formula:

[0077]

[0078] Among them, i n u n Let I represent the instantaneous values ​​of the equivalent current source and the equivalent voltage source, respectively. n U n ω represents the peak values ​​of the equivalent current source and the equivalent voltage source, respectively; φ represents the angular velocity corresponding to the power frequency quantity; φ represents the phase angle of the voltage leading the current; and t represents time.

[0079] During the first switching phase, the voltages of the first auxiliary switching element V1, the second auxiliary switching element V2, and the third auxiliary switching element V3 are zero, and the currents of the first auxiliary switching element V1 and the third auxiliary switching element V3 are zero. The voltage of the second auxiliary switching element V2 is determined based on the voltage of the vacuum on-load tap changer transition circuit. The specific voltages and currents borne by each switching element (V1, V2, V3) in the transition circuit are as follows:

[0080]

[0081] Among them, U V1 U V2 U V3 I represents the voltages that the first auxiliary switching element, the second auxiliary switching element, and the third auxiliary switching element withstand, respectively. V1 I V2 I V3 These represent the currents carried by the first auxiliary switching element, the second auxiliary switching element, and the third auxiliary switching element, respectively.

[0082] Second switching phase: The first main switch MC1 is disconnected. At this time, the second main switch MC2 remains disconnected, the third auxiliary switch element V3 and the first auxiliary switch element V1 remain on, the second auxiliary switch element V2 remains disconnected, the changeover switch T remains in the state of the first moving contact 11, the first winding tap (N) continues to be connected, and the load current flows out from the neutral point (0) lead-out terminal through the changeover switch T and the third auxiliary switch element V3. Figure 5 As shown.

[0083] In the second switching phase, the voltages of the first auxiliary switching element V1 and the third auxiliary switching element V3 are zero, and the currents of the first auxiliary switching element V1 and the second auxiliary switching element V2 are zero. The voltage of the second auxiliary switching element V2 is determined based on the voltage of the vacuum on-load tap changer transition circuit, and the current of the third auxiliary switching element V3 is determined based on the current of the vacuum on-load tap changer transition circuit. The specific voltages and currents borne by each switching element (V1, V2, V3) in the transition circuit are as follows:

[0084]

[0085] Third switching phase: The first main switch MC1 remains open, the second main switch MC2 remains open, and the third auxiliary switch element V3 is disconnected. At this time, an electric arc is generated in the third auxiliary switch element V3. The first auxiliary switch element V1 remains on, the second auxiliary switch element V2 remains off, the changeover switch T remains in the state of the first moving contact 11, the first winding tap continues to be connected, and the load current flows out from the neutral point (0) lead-out terminal through the changeover switch T and the first transition resistor R1. Figure 6 As shown.

[0086] In the third switching phase, the voltages of the first auxiliary switching element V1 and the third auxiliary switching element V3 are zero, and the currents of the second auxiliary switching element V2 and the third auxiliary switching element V3 are zero. The voltage of the second auxiliary switching element V2 is determined based on the voltage of the vacuum on-load tap changer transition circuit, and the current of the first auxiliary switching element V1 is determined based on the current of the vacuum on-load tap changer transition circuit. The specific voltages and currents borne by each switching element (V1, V2, V3) in the transition circuit are as follows:

[0087]

[0088] Fourth switching stage: The first main switch MC1 remains open, the second main switch MC2 remains open, the third auxiliary switch element V3 remains open, the first auxiliary switch element V1 remains on, and the second auxiliary switch element V2 remains open. After the arc inside the third auxiliary switch element V3 is extinguished, the first moving contact 11 of the changeover switch T is opened, and the second moving contact 12 of the changeover switch T is turned on (that is, the changeover switch T is switched from the state of the first moving contact 11 to the state of the second moving contact 12). The first winding tap (N) remains on, and the load current flows out from the neutral point (0) lead-out terminal through the first auxiliary switch element V1 and the first transition resistor R1. Figure 7 As shown.

[0089] In the fourth switching phase, the voltages of the first auxiliary switching element V1 and the third auxiliary switching element V3 are zero, and the currents of the second auxiliary switching element V2 and the third auxiliary switching element V3 are zero. The voltage of the second auxiliary switching element V2 is determined based on the voltage of the vacuum on-load tap changer transition circuit and the voltage of the first transition resistor R1. The current of the first auxiliary switching element V1 is determined based on the current of the vacuum on-load tap changer transition circuit. The specific voltages and currents borne by each switching element (V1, V2, V3) in the transition circuit are as follows:

[0090]

[0091] Wherein, R1 represents the resistance value of the first transition resistor R1.

[0092] Fifth switching stage: The first main switch MC1 remains open, the second main switch MC2 remains open, the third auxiliary switch element V3 remains open, the first auxiliary switch element V1 remains on, the second auxiliary switch element V2 is closed and on, the changeover switch T remains in the state of the second moving contact 12, the first winding tap (N) and the second winding tap (N+1) are both connected, the load current flows out from the neutral point (0) through the two paths of the first transition resistor R1 and the second transition resistor R2, the first path is the first auxiliary switch element V1 and the first transition resistor R1, the second path is the second auxiliary switch element V2, the changeover switch T and the second transition resistor R2; the transition circuit forms a bridge, generating an interstage circulating current I. c ,like Figure 8 As shown.

[0093] In the fifth switching phase, the voltages of the first auxiliary switching element V1 and the second auxiliary switching element V2 are zero, and the current of the third auxiliary switching element V3 is zero. The voltage of the third auxiliary switching element V3 is determined based on the voltage and current of the vacuum on-load tap changer transition circuit, and the resistance values ​​of the first transition resistor R1 and the second transition resistor R2. The currents of the first auxiliary switching element V1 and the second auxiliary switching element V2 are determined based on the current of the vacuum on-load tap changer transition circuit, and the resistance values ​​of the first transition resistor R1 and the second transition resistor R2. The specific voltages and currents borne by each switching element (V1, V2, V3) in the transition circuit are as follows:

[0094]

[0095] Where R2 represents the resistance value of the second transition resistor R2.

[0096] Sixth switching stage: The first main switch MC1 remains open, the second main switch MC2 remains open, and the third auxiliary switch element V3 remains open. The first auxiliary switch element V1 is disconnected. At this time, an electric arc is generated in the first auxiliary switch element V1. The second auxiliary switch element V2 remains closed. The changeover switch T maintains the state of the second moving contact 12. The second winding tap (N+1) is connected. The load current flows out from the neutral point (0) lead-out terminal through the second auxiliary switch element V2, the changeover switch T, and the second transition resistor R2. Figure 9 As shown.

[0097] In the sixth switching stage, the voltage of the second auxiliary switching element V2 is zero, and the currents of the first auxiliary switching element V1 and the second auxiliary switching element V2 are zero. The voltage of the first auxiliary switching element V1 is determined based on the voltage and current of the vacuum on-load tap changer transition circuit and the resistance value of the second transition resistor R2. The voltage of the third auxiliary switching element V3 is determined based on the current of the vacuum on-load tap changer transition circuit and the resistance value of the second transition resistor R2. The current of the second auxiliary switching element V2 is determined based on the current of the vacuum on-load tap changer transition circuit. The specific voltages and currents borne by each switching element (V1, V2, V3) in the transition circuit are as follows:

[0098]

[0099] Seventh switching stage: The first main switch MC1 remains open, the second main switch MC2 remains open, and after the arc inside the first auxiliary switch element V1 is extinguished, the third auxiliary switch element V3 is closed and turned on. The first auxiliary switch element V1 remains open, the second auxiliary switch element V2 remains closed, the changeover switch T remains in the state of the second moving contact 12, the second winding tap (N+1) remains connected, and the load current flows out from the neutral point (0) lead-out terminal through the second auxiliary switch element V2 and the third auxiliary switch element V3. Figure 10 As shown.

[0100] In the seventh switching stage, the voltages of the second auxiliary switching element V2 and the third auxiliary switching element V3 are zero, and the current of the first auxiliary switching element V1 is zero. The voltage of the first auxiliary switching element V1 is determined based on the voltage of the vacuum on-load tap changer transition circuit, and the currents of the second auxiliary switching element V2 and the third auxiliary switching element V3 are determined based on the current of the vacuum on-load tap changer transition circuit. The specific voltages and currents borne by each switching element (V1, V2, V3) in the transition circuit are as follows:

[0101]

[0102] Eighth switching stage: The first main switch MC1 remains open, the second main switch MC1 is closed and turned on, the third auxiliary switch element V3 remains closed, the first auxiliary switch element V1 remains open, the second auxiliary switch element V2 remains closed, the changeover switch T maintains the state of the second moving contact 12, the second winding tap (N+1) continues to be connected, and the load current flows from the second winding tap (N+1) through the second main switch MC2 from the neutral point (0) lead-out terminal, completing the switching process of the on-load tap changer from the first winding tap (N) to the second winding tap (N+1), as follows. Figure 11 As shown.

[0103] In the eighth switching stage, the voltages of the second auxiliary switching element V2 and the third auxiliary switching element V3 are zero, and the currents of the first auxiliary switching element V1, the second auxiliary switching element V2, and the third auxiliary switching element V3 are zero. The voltage of the first auxiliary switching element V1 is determined based on the voltage of the vacuum on-load tap changer transition circuit. The specific voltages and currents borne by each switching element (V1, V2, V3) in the transition circuit are as follows:

[0104]

[0105] When the on-load tap changer switches from the second winding tap (N+1) to the first winding tap (N), the switching phase of the transition circuit can also be divided into eight switching phases. The specific voltage regulation process is as follows:

[0106] First switching phase: The first main switch remains open, the second main switch and the third auxiliary switch remain closed and conducting, the first auxiliary switch remains open, the second auxiliary switch remains closed and conducting, the changeover switch remains in the state of the second moving contact, the second winding tap is connected, and the load current flows out from the second winding tap through the second main switch from the neutral point lead-out terminal;

[0107] Second switching phase: The first main switch remains open, the second main switch is opened, the third auxiliary switch element remains closed and conducting, the first auxiliary switch element remains open, the second auxiliary switch element remains closed and conducting, the changeover switch remains in the state of the second moving contact, the second winding tap is connected, and the load current flows out from the neutral point lead-out terminal through the second auxiliary switch element.

[0108] Third switching stage: The first main switch remains open, the second main switch remains open, the third auxiliary switch element is disconnected, at this time, an electric arc is generated in the third auxiliary switch element, the first auxiliary switch element remains open, the second auxiliary switch element remains closed and conducting, the changeover switch remains in the state of the second moving contact, the second winding tap continues to be connected, and the load current flows out from the neutral point lead-out terminal through the second auxiliary switch element, the changeover switch, and the second transition resistor.

[0109] Fourth switching stage: The first main switch remains open, the second main contact remains open, and the third auxiliary switch element remains open. After the arc inside the third auxiliary switch element is extinguished, the first auxiliary switch element is closed and turned on, the second auxiliary switch element remains closed and turned on, the changeover switch remains in the state of the second moving contact, and both the first winding tap and the second winding tap are turned on. The load current flows out from the neutral point lead-out terminal through the two paths containing the first transition resistor and the second transition resistor. The first path is the first auxiliary switch element and the first transition resistor, and the second path is the second auxiliary switch element, the changeover switch, and the second transition resistor. The transition circuit forms a bridge, generating interstage circulating current.

[0110] Fifth switching stage: The first main switch remains open, the second main contact remains open, the third auxiliary switch element remains open, the first auxiliary switch element remains closed and conducting, the second auxiliary switch element is opened, an electric arc is generated in the second auxiliary switch element, the changeover switch maintains the state of the second moving contact, the first winding tap is connected, and the load current flows out from the neutral point lead-out terminal through the first auxiliary switch element and the first transition resistor;

[0111] Sixth switching stage: The first main switch remains open, the second main contact remains open, the third auxiliary switch element remains open, the first auxiliary switch element remains closed and conducting, and the second auxiliary switch element remains open. After the arc in the second auxiliary switch element is extinguished, the second moving contact of the changeover switch is opened, and the first moving contact of the changeover switch is turned on (i.e., the changeover switch switches from the second moving contact state to the first moving contact state). The first winding tap remains connected, and the load current flows out from the neutral point lead-out through the first auxiliary switch element and the first transition resistor.

[0112] Seventh switching stage: The first main switch remains open, the second main contact remains open, the third auxiliary switch element is closed and turned on, the first auxiliary switch element remains closed, the second auxiliary switch element remains open, the changeover switch remains in the state of the first moving contact, the first winding tap is turned on, and the load current flows out from the neutral point lead-out terminal through the changeover switch and the third auxiliary switch element.

[0113] Eighth switching stage: The first main switch is turned on. At this time, the second main switch remains open, the third auxiliary switch element remains closed and turned on, the second auxiliary switch element remains open, the changeover switch remains in the first moving contact state, the first winding tap continues to be connected, and the load current flows out from the first winding tap through the first main switch from the neutral point, completing the switching process of the on-load tap changer from the second winding tap to the first winding tap.

[0114] It should be noted that the calculation process for the voltage and current of each switching element in the transition circuit during the various stages of the on-load tap changer switching from the second winding tap (N+1) to the first winding tap (N) can be found in the above-mentioned calculation process for the voltage and current of each switching element in the transition circuit during the various stages of the on-load tap changer switching from the first winding tap (N) to the second winding tap (N+1), and will not be repeated here.

[0115] The first auxiliary switching element, the second auxiliary switching element, and the third auxiliary switching element can be any one of a single-break vacuum circuit breaker (or a single-break vacuum contact), a double-break vacuum circuit breaker (or a double-break vacuum contact), or a power electronic component with controllable switching function.

[0116] Power electronic components with controllable switching functions include, but are not limited to, insulated gate bipolar transistors (IGBTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0117] It should be understood that when the internal switching elements (V1, V2, V3) in the vacuum on-load tap changer transition circuit are power electronic components with controllable switching functions, double-break vacuum contacts, or single-break vacuum contacts, the operating timing and voltage regulation method of the switching elements are consistent.

[0118] In this embodiment of the invention, the switching tasks of the vacuum on-load tap changer transition circuit using a first auxiliary switching element, a second auxiliary switching element, and a third auxiliary switch are shown in the table below:

[0119]

[0120]

[0121] Among them, I N U represents the load current; SR1 represents the voltage between the on-load tap changer stages; R2 represents the resistance value of the first transition resistor R1 and the second transition resistor R2.

[0122] When the on-load tap changer switches from tapping the first winding (N) to tapping the second winding (N+1), the transition circuit switching procedure is as follows: Figure 12 As shown;

[0123] When the on-load tap changer switches from the second winding tap (N+1) to the first winding tap (N), the transition circuit switching procedure is as follows: Figure 13 As shown;

[0124] Figure 14 The circuit diagram shows a vacuum on-load tap changer transition circuit (which can also be described as a reciprocating on-load tap changer transition circuit with alternating vacuum tube switching) formed when the switching elements (V1, V2, V3) in the transition circuit are power electronic components, as follows: Figure 14 As shown, only Figure 2 In the intermediate transition circuit, the switching elements (V1, V2, V3) are replaced from single-break vacuum contacts with power electronic components that can control on and off. Other components are... Figure 2 The components are the same, the timing of their actions is consistent, and their functions and roles are identical. Figure 2 The function and role of the transition circuit shown are the same, and will not be repeated here.

[0125] Figure 15 The circuit diagram of the vacuum on-load tap changer transition circuit formed when the switching elements (V1, V2, V3) in the transition circuit are power electronic components; for example... Figure 15 As shown, only Figure 2 The switching elements (V1, V2, V3) in the intermediate transition circuit are replaced from single-break vacuum contacts to double-break vacuum contacts; other components are the same as... Figure 2 The components are the same, the timing of their actions is consistent, and their functions and roles are identical. Figure 2 The function and role of the transition circuit shown are the same, and will not be repeated here.

[0126] During the reciprocating switching process of the vacuum on-load tap changer transition circuit, the third auxiliary switching element V3 undertakes the task of interrupting the load current, while the first auxiliary switching element V1 and the second auxiliary switching element V2 undertake the task of interrupting the superimposed interstage circulating current of the load current. The switching elements take turns to share the switching task, which can effectively reduce the switching loss of the switching elements (i.e., vacuum contacts) and extend the service life of the transition circuit. At the same time, the reciprocating switching sequence is reversible, which can improve the reliability and switching efficiency of the on-load tap changer. In addition, during the switching process, the embodiment of the present invention adjusts the voltage and current of each switching element, improves the withstand capability when subjected to overcurrent and overvoltage, and clarifies the unique characteristics of the switching elements in the transition circuit under electrical stress during the switching process, enabling it to adapt to different switching requirements.

[0127] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, many improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A vacuum on-load tap changer transition circuit, characterized by, The application relates to a vacuum on-load tap-changer transition circuit and a voltage regulation method. The on-load tap-changer comprises a first main switch and a second main switch, and the transition circuit comprises a conversion switch, a first transition branch, a second transition branch and a third transition branch. One end of the first main switch is connected with a first winding tap of a voltage regulation winding of a transformer, one end of the second main switch is connected with a second winding tap of the voltage regulation winding of the transformer, and the other ends of the first main switch and the second main switch are connected with a neutral point of the transformer; the first transition branch is connected in parallel with the first main switch; the third transition branch is connected in parallel with the second main switch; a static contact of the conversion switch is connected with a first output end of the third transition branch; a first moving contact of the conversion switch is connected with an input end of the first transition branch, a second moving contact of the conversion switch is connected with an input end of the second transition branch, and an output end of the second transition branch is connected with the neutral point of the transformer. The first transition branch comprises a first auxiliary switch element and a first transition resistor; one end of the first auxiliary switch element is connected with an input end of the first transition branch, the other end of the first auxiliary switch element is connected with one end of the first transition resistor, and the other end of the first transition resistor is connected with an output end of the first transition branch; the input end of the first transition branch is connected with the first winding tap of the voltage regulation winding of the transformer, and the output end of the first transition branch is connected with the neutral point of the transformer. The second transition branch comprises a second transition resistor; one end of the second transition resistor is connected with an input end of the second transition branch, and the other end of the second transition resistor is connected with an output end of the second transition branch. The third transition branch comprises a second auxiliary switch element and a third auxiliary switch element; an input end of the second auxiliary switch element is connected with an input end of the third transition branch, an output end of the second auxiliary switch element and an input end of the third auxiliary switch element are connected with a first output end of the third transition branch, and an output end of the third auxiliary switch element is connected with a second output end of the third transition branch; the input end of the third transition branch is connected with the second winding tap of the voltage regulation winding of the transformer, and the second output end of the third transition branch is connected with the neutral point of the transformer. The application also discloses a voltage regulation method.

2. A method of regulating the voltage of a vacuum on-load tap changer transition circuit, characterized in that The on-off of the first main switch and the second main switch is used for controlling the switching of the on-load tap-changer between the first winding tap and the second winding tap. The on-off of the first moving contact and the second moving contact of the conversion switch is used for controlling the communication or disconnection between the third transition branch and the first transition branch and the second transition branch. ​ By turning on and off the first auxiliary switching element, the second auxiliary switching element and the third auxiliary switching element, the opening and closing of the load current in each branch of the transition circuit of the vacuum on-load tap changer is controlled, so that the load current flows out from the neutral point outlet end through the first winding tap or the second winding tap via the first main switch or the second main switch, to adjust the voltage of each switching element in the transition circuit during switching.

3. The voltage regulating method of the vacuum on-load tap changer transition circuit according to claim 2, characterized in that, The method comprises: When the first main switch, the third auxiliary switching element and the first auxiliary switching element are in the on state, the second auxiliary switching element and the second main switch are in the off state, and the first movable contact of the switch is in the on state, the first winding tap is connected, and the load current flows out from the neutral point outlet end through the first main switch; The first main switch is turned off, the first winding tap continues to be connected, and the load current flows out from the neutral point outlet end through the switch and the third auxiliary switching element; The third auxiliary switching element is turned off, the first winding tap continues to be connected, and the load current flows out from the neutral point outlet end through the switch and the first transition resistor; The first movable contact of the switch is turned off, the second movable contact of the switch is turned on, the first winding tap continues to be connected, and the load current flows out from the neutral point outlet end through the first auxiliary switching element and the first transition resistor; The second auxiliary switching element is turned on, the second movable contact of the switch is turned on, the first winding tap and the second winding tap are both connected, and the load current flows out from the neutral point outlet end through the first transition resistor and the second transition resistor; The first auxiliary switching element is turned off, the second winding tap is connected, and the load current flows out from the neutral point outlet end through the second auxiliary switching element, the switch and the second transition resistor; The third auxiliary switching element is turned on, the second winding tap is connected, and the load current flows out from the neutral point outlet end through the second auxiliary switching element and the third auxiliary switching element; The second main switch is turned on, the second winding tap is connected, and the load current flows out from the neutral point outlet end through the second main switch, completing the switching process of the on-load tap changer from the first winding tap to the second winding tap.

4. The voltage regulating method of a vacuum on-load tap changer transition circuit according to claim 3, characterized in that, The method comprises: When the second main switch, the third auxiliary switching element and the second auxiliary switching element are in the on state, the first auxiliary switching element is in the off state, and the second movable contact of the switch is in the on state, the second winding tap is connected, and the load current flows out from the neutral point outlet end through the second main switch; The second main switch is turned off, the second winding tap is connected, and the load current flows out from the neutral point outlet end through the second auxiliary switching element and the second auxiliary switching element; The third auxiliary switch element is turned off, the second winding tap continues to be turned on, and the load current flows out from the neutral point outlet end through the second auxiliary switch element, the transfer switch, and the second transition resistor; The first auxiliary switch element is turned on, the second winding tap and the first winding tap are both turned on, and the load current flows out from the neutral point outlet end through the first transition resistor and the second transition resistor; The second auxiliary switch element is turned off, the first winding tap is turned on, and the load current flows out from the neutral point outlet end through the first auxiliary switch element and the first transition resistor; The second movable contact of the transfer switch is turned off, the first movable contact of the transfer switch is turned on, the first winding tap is turned on, and the load current flows out from the neutral point outlet end through the first auxiliary switch element and the first transition resistor; The third auxiliary switch element is turned on, the first winding tap is turned on, and the load current flows out from the neutral point outlet end through the transfer switch and the third auxiliary switch element; The first main switch is turned on, the first winding tap is turned on, and the load current flows out from the first winding tap through the first main switch from the neutral point outlet end, completing the switching process of the on-load tap changer from the second winding tap to the first winding tap.

5. The voltage regulating method of the vacuum on-load tap changer transition circuit according to claim 3, characterized in that, The method comprises: When the first winding tap is turned on and the load current flows out from the first winding tap through the first main switch from the neutral point outlet end, the voltages of the first auxiliary switch element, the second auxiliary switch element, and the third auxiliary switch element are zero, the currents of the first auxiliary switch element and the third auxiliary switch element are zero, and the voltage of the second auxiliary switch element is determined according to the voltage of the vacuum on-load tap changer transition circuit; When the first winding tap continues to be turned on and the load current flows out from the neutral point outlet end through the transfer switch and the third auxiliary switch element, the voltages of the first auxiliary switch element and the third auxiliary switch element are zero, the currents of the first auxiliary switch element and the second auxiliary switch element are zero, the voltage of the second auxiliary switch element is determined according to the voltage of the vacuum on-load tap changer transition circuit, and the current of the third auxiliary switch element is determined according to the current of the vacuum on-load tap changer transition circuit.

6. The voltage regulating method of a vacuum on-load tap changer transition circuit according to claim 5, characterized in that, The method comprises: When the first winding tap continues to be turned on and the load current flows out from the neutral point outlet end through the transfer switch and the first transition resistor, the voltages of the first auxiliary switch element and the third auxiliary switch element are zero, the currents of the second auxiliary switch element and the third auxiliary switch element are zero, the voltage of the second auxiliary switch element is determined according to the voltage of the vacuum on-load tap changer transition circuit, and the current of the first auxiliary switch element is determined according to the current of the vacuum on-load tap changer transition circuit. When the load current flows out from the neutral point outlet through the first auxiliary switching element and the first transition resistor, the voltage of the first auxiliary switching element and the third auxiliary switching element is zero, the current of the second auxiliary switching element and the third auxiliary switching element is zero, the voltage of the second auxiliary switching element is determined according to the voltage of the vacuum on-load tap changer transition circuit and the voltage of the first transition resistor, and the current of the first auxiliary switching element is determined according to the current of the vacuum on-load tap changer transition circuit. When the load current flows out from the neutral point outlet through the first transition resistor and the second transition resistor with the first winding tap and the second winding tap being connected, the voltage of the first auxiliary switching element and the second auxiliary switching element is zero, the current of the third auxiliary switching element is zero, the voltage of the third auxiliary switching element is determined according to the voltage and current of the vacuum on-load tap changer transition circuit and the resistance values of the first transition resistor and the second transition resistor, and the current of the first auxiliary switching element and the second auxiliary switching element is determined according to the current of the vacuum on-load tap changer transition circuit and the resistance values of the first transition resistor and the second transition resistor.

7. The voltage regulating method of a vacuum on-load tap changer transition circuit according to claim 6, characterized in that, The method comprises: When the load current flows out from the neutral point outlet through the second auxiliary switching element, the transition switch and the second transition resistor with the second winding tap being connected, the voltage of the second auxiliary switching element is zero, the current of the first auxiliary switching element and the second auxiliary switching element is zero, the voltage of the first auxiliary switching element is determined according to the voltage and current of the vacuum on-load tap changer transition circuit and the resistance value of the second transition resistor, and the voltage of the third auxiliary switching element is determined according to the current of the vacuum on-load tap changer transition circuit and the resistance value of the second transition resistor, and the current of the second auxiliary switching element is determined according to the current of the vacuum on-load tap changer transition circuit. When the load current flows out from the neutral point outlet through the second auxiliary switching element and the third auxiliary switching element with the second winding tap being connected, the voltage of the second auxiliary switching element and the third auxiliary switching element is zero, the current of the first auxiliary switching element is zero, the voltage of the first auxiliary switching element is determined according to the voltage of the vacuum on-load tap changer transition circuit, and the current of the second auxiliary switching element and the third auxiliary switching element is determined according to the current of the vacuum on-load tap changer transition circuit. When the load current flows out from the neutral point outlet through the second winding tap and the second main switch with the second winding tap being connected, the voltage of the second auxiliary switching element and the third auxiliary switching element is zero, the current of the first auxiliary switching element, the second auxiliary switching element and the third auxiliary switching element is zero, and the voltage of the first auxiliary switching element is determined according to the voltage of the vacuum on-load tap changer transition circuit.

Images