A reciprocating transition circuit and voltage regulation method for an on-load tap changer

Abstract

The present invention discloses a reciprocating transition circuit and voltage regulation method for an on-load tap changer, the circuit comprising: a first main through-current switch, a second main through-current switch, a first switch element, a second switch element, a third switch element, a fourth switch element, a first transition resistor and a second transition resistor; the second end of the first switch element, the first end of the second switch element and the first end of the first transition resistor are connected; the second end of the third switch element, the first end of the fourth switch element and the first end of the second transition resistor are connected; the second end of the first main through-current switch, the second end of the second switch element, the second end of the first transition resistor, the second end of the second main through-current switch, the second end of the fourth switch element and the second end of the second transition resistor are all used to connect to the neutral point lead-out terminal of the on-load tap changer. The present invention realizes on-load switching and voltage regulation entirely by switch elements and transition resistors; and no mechanical track-changing mechanism is required.

Description

Technical Field

[0001] The invention belongs to the technical field of on-load tap changers, and in particular relates to a reciprocating transition circuit and a voltage regulating method for an on-load tap changer. Background Art

[0002] The on-load tap changer is a key component inside the power transformer. It can operate under the transformer excitation or load state. By changing the number of taps connected to the transformer winding, the effective turns ratio is changed to adjust the output voltage without interrupting the load current. The on-load tap changer has a wide range of applications, especially in the converter transformer of the UHV DC transmission project, to ensure the rated trigger angle of the converter during normal operation.

[0003] Most of the on-load tap-changers equipped with early power transformers adopted the principle of high-speed resistance switching, relying on copper-tungsten arc contacts for load conversion; this type of oil-immersed non-vacuum on-load tap-changer switches frequently, the arc contacts burn out more seriously, and the oil carbonizes and pollutes faster, which increases the workload of daily maintenance and regular inspections for the power supply department. The vacuum on-load tap-changer mainly uses vacuum tubes to extinguish the arc, avoiding the carbonization and pollution of the oil caused by the arc extinguishing in the oil; due to the short arc-breaking time, low arc voltage, low arc energy consumption and recondensation of contact metal vaporization of the vacuum tube, the contact burning and corrosion can be minimized. The power electronic on-load tap-changer replaces the vacuum tube with power electronic components to achieve arc-free operation during the on-load switching process.

[0004] The on-load tap changer consists of a transfer switch, a tap selector and an electric mechanism; among them, the transfer switch has an independent oil chamber and is the key component for the tap changer to achieve on-load switching. Its core is the use of a transition circuit. Vacuum on-load tap changers can be divided into single-contact circuits, double-contact circuits, three-contact circuits and four-contact circuits according to the number of vacuum tubes; there are two types of transitions: single resistor and double resistor according to the number of transition resistors; there are single break and double break according to the number of contact breaks; the above combinations can constitute different types of transition circuits for vacuum on-load tap changers. The switching elements 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 voltage regulation, and the switching tasks of each switching element will also be different. The topological structure 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.

[0005] The existing on-load tap changers all use oil-immersed mechanical contact transfer switches, which easily cause the mechanical structure of the transfer switch to be complicated. Once the timing coordination error occurs, it will inevitably cause the transfer switch to extinguish the arc in the oil. After multiple arc extinguishing in the oil, the transformer oil will be seriously polluted, carbon will accumulate, and the insulation performance will be reduced, which will cause the arc in the oil to be unable to be extinguished, posing a great safety risk. The control timing of the existing vacuum on-load tap changer transition circuit switching from winding tap N to winding tap N+1 and from winding tap N+1 to winding tap N is asymmetric. In the process of mechanical reciprocating motion of the switching core, the cam mechanism needs to realize lifting and pulling track change, which increases the complexity of mechanical manufacturing and the failure rate of switch use. Summary of the invention

[0006] The object of the present invention is to provide a reciprocating transition circuit and voltage regulation method for an on-load tap changer, so as to solve one or more of the above-mentioned technical problems. In the present invention, the transition circuit completely realizes on-load voltage regulation by means of switch elements and transition resistors, avoiding the problem of arc extinction in oil caused by the use of mechanical contact conversion switches, so as to improve the reliability and electrical life of the on-load tap changer; in addition, the mechanical on-load tap changer using the transition circuit has a mirror-symmetric action sequence during the forward and reverse reciprocating switching process, and does not require a mechanical track-changing mechanism.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A reciprocating transition circuit of an on-load tap changer of the present invention comprises: a first main through-current switch, a second main through-current switch, a first switch element, a second switch element, a third switch element, a fourth switch element, a first transition resistor and a second transition resistor;

[0009] The first end of the first main pass-through switch is connected to the first end of the first switch element, and both are used to be connected to the first winding tap N of the transformer voltage regulating winding; the first end of the second main pass-through switch is connected to the first end of the third switch element, and both are used to be connected to the second winding tap N+1 of the transformer voltage regulating winding;

[0010] The second end of the first switch element, the first end of the second switch element, and the first end of the first transition resistor are connected;

[0011] The second end of the third switch element, the first end of the fourth switch element, and the first end of the second transition resistor are connected;

[0012] The second end of the first main pass-through switch, the second end of the second switching element, the second end of the first transition resistor, the second end of the second main pass-through switch, the second end of the fourth switching element, and the second end of the second transition resistor are all used to be connected to the neutral point lead-out terminal of the on-load tap changer.

[0013] A further improvement of the present invention is that the first switch element, the second switch element, the third switch element or the fourth switch element is a single-break vacuum tube, a double-break vacuum tube or a power electronic element with a controllable on-off function.

[0014] A further improvement of the present invention is that it also includes: a transformer voltage regulating winding;

[0015] The first end of the first main current-carrying switch and the first end of the first switching element are both connected to the first winding tap N of the transformer voltage regulating winding;

[0016] The first end of the second main pass-through switch and the first end of the third switch element are both connected to the second winding tap N+1 of the transformer voltage regulating winding.

[0017] A further improvement of the present invention is that it also includes: an on-load tap changer;

[0018] The second end of the first main pass-through switch, the second end of the second switching element, the second end of the first transition resistor, the second end of the second main pass-through switch, the second end of the fourth switching element, and the second end of the second transition resistor are all connected to the neutral point lead-out terminal of the on-load tap changer.

[0019] A further improvement of the present invention is that, during the reciprocating switching process of the on-load tap changer transition circuit, the second switch element and the fourth switch element are used to take turns to assume the task of breaking the load current; the first switch element and the third switch element are used to take turns to assume the task of breaking the inter-stage circulating current.

[0020] A further improvement of the present invention is that the first transition resistor and the second transition resistor are used to limit the inter-stage circulating current when the first winding tap N and the second winding tap N+1 of the transformer voltage regulating winding are bridged.

[0021] A voltage regulating method for a reciprocating transition circuit of an on-load tap changer of the present invention comprises the following steps:

[0022] The first main pass-through switch, the first switch element, and the second switch element are all in an on state; the second main pass-through switch, the third switch element, and the fourth switch element are all in an off state;

[0023] Disconnecting the first main current-carrying switch;

[0024] Turning off the second switch element and turning on the third switch element;

[0025] Turning off the first switch element and turning on the fourth switch element;

[0026] The second main current-carrying switch is turned on to allow the load current to flow out from the second winding tap N+1 through the second main current-carrying switch from the neutral point, and the switching process of the on-load tap changer from the first winding tap N to the second winding tap N+1 is completed.

[0027] A voltage regulating method for a reciprocating transition circuit of an on-load tap changer of the present invention comprises the following steps:

[0028] The second main pass-through switch, the third switch element, and the fourth switch element are all in an on state; the first main pass-through switch, the first switch element, and the second switch element are all in an off state;

[0029] Disconnecting the second main flow switch;

[0030] Turning off the fourth switch element and turning on the first switch element;

[0031] Turning off the third switch element and turning on the second switch element;

[0032] The first main current-carrying switch is turned on to allow the load current to flow out from the neutral point through the first winding tap N via the first main current-carrying switch, and the switching process of the on-load tap changer from the second winding tap N+1 to the first winding tap N is completed.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] In the present invention, the transition circuit is completely composed of switch elements and transition resistors to achieve on-load switching and voltage regulation, avoiding the problem of arc extinction in the oil caused by the use of mechanical contact conversion switches, so as to improve the reliability and electrical life of the on-load tap changer; in addition, the mechanical on-load tap changer using the transition circuit has a mirror-symmetric action sequence during the forward and reverse reciprocating switching process, and no mechanical track-changing mechanism is required. Specifically, in the reciprocating transition circuit of the on-load tap changer provided by the present invention, the transition circuit is completely composed of switch elements and transition resistors, and there is no problem of arc extinction in the oil; the transition circuit has a mirror-symmetric action sequence during the forward and reverse reciprocating switching process, avoiding the mechanical structure track-changing operation; the transition circuit is designed with two transition resistors for current limiting, avoiding the problem of transformer oil decomposition and gas production and insulation degradation due to the concentrated heat generation of a single transition resistor causing the transition resistor to be too high in temperature.

[0035] In the present invention, the second switch element and the fourth switch element take turns to take the task of breaking the load current, and the first switch element and the third switch element take turns to take the task of breaking the inter-stage circulating current, which reduces the working loss of a single switch element, balances the switching capacity between the switch elements, and reduces the failure rate of the switch elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 A circuit diagram of an on-load tap changer transition circuit according to an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of a transition circuit switching process of an on-load tap changer according to an embodiment of the present invention;

[0039] Figure 3 A schematic diagram of a transition circuit switching process of an on-load tap changer according to an embodiment of the present invention;

[0040] Figure 4 A schematic diagram of a transition circuit switching process of an on-load tap changer according to an embodiment of the present invention;

[0041] Figure 5 A schematic diagram of a transition circuit switching process of an on-load tap changer according to an embodiment of the present invention;

[0042] Figure 6 A schematic diagram of a transition circuit switching process of an on-load tap changer according to an embodiment of the present invention;

[0043] Figure 7 A schematic diagram of a transition circuit switching process of an on-load tap changer according to an embodiment of the present invention;

[0044] Figure 8 It is a schematic diagram of the on-off of each switch in the transition circuit of the on-load tap changer according to an embodiment of the present invention when the load is switched from the winding tap N to the winding tap N+1;

[0045] Fig. 9 It is a schematic diagram of the switching on and off of each switch in the transition circuit of the on-load tap changer according to an embodiment of the present invention when the load is switched from the winding tap N+1 to the winding tap N;

[0046] Fig.10A circuit diagram of a reciprocating transition circuit of an on-load tap changer in which the switch element is a power electronic element according to an embodiment of the present invention;

[0047] Fig.11 The circuit diagram of the reciprocating transition circuit of an on-load tap changer whose switching element is a double-break vacuum tube according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0049] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0050] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0051] A reciprocating transition circuit of an on-load tap changer according to an embodiment of the present invention comprises: a first main through-current switch, a second main through-current switch, a first switching element, a second switching element, a third switching element, a fourth switching element, a first transition resistor and a second transition resistor; wherein the first end of the first main through-current switch is connected to the first end of the first switching element, and both are used to be connected to a first winding tap N of a voltage regulating winding of a transformer; the first end of the second main through-current switch is connected to the first end of the third switching element, and both are used to be connected to a second winding tap N+1 of a voltage regulating winding of a transformer; the second end of the first switching element, the first end of the second switching element, and the first end of the first transition resistor are connected; the second end of the third switching element, the first end of the fourth switching element, and the first end of the second transition resistor are connected; the second end of the first main through-current switch, the second end of the second switching element, the second end of the first transition resistor, the second end of the second main through-current switch, the second end of the fourth switching element, and the second end of the second transition resistor are all used to be connected to a neutral point lead-out terminal of the on-load tap changer.

[0052] Furthermore, the first switch element, the second switch element, the third switch element or the fourth switch element is a single-break vacuum tube, a double-break vacuum tube or a power electronic element with a controllable on-off function.

[0053] In the embodiment of the present invention, the first main current-carrying switch and the second main current-carrying switch are used for long-term current carrying of load current; the second switch element and the fourth switch element are used to interrupt the load current during the switching process, and the first switch element and the third switch element are used to interrupt the inter-stage circulating current during the switching process; the first transition resistor and the second transition resistor are used to limit the inter-stage circulating current when the first winding tap N and the second winding tap N+1 of the transformer voltage regulating winding are bridged. Exemplarily, the actual selection specifications of each component are determined by the actual working conditions of the transition circuit.

[0054] Figure 1 FIG. 1 is a circuit diagram of a reciprocating transition circuit of an on-load tap changer according to an embodiment of the present invention. Figure 1As shown, the present invention provides a reciprocating transition circuit of an on-load tap changer. The transition circuit is completely composed of switch elements and transition resistors, and there is no problem of arc extinction in the oil. The second vacuum tube V2 and the fourth vacuum tube V4 take turns to take on the task of breaking the load current, and the first vacuum tube V1 and the third vacuum tube V3 take turns to take on the task of breaking the inter-stage circulation current, which reduces the working loss of a single switch element, balances the switching capacity between the switch elements, and reduces the failure rate of the switch elements. In the process of forward and reverse reciprocating switching, the action sequence of the transition circuit is mirror-symmetrical, avoiding the mechanical structure track change operation. The transition circuit is designed Two transition resistors are designed to limit the current, so as to avoid the problem that the temperature of the transition resistor is too high due to the concentrated heat of the single transition resistor, which leads to the decomposition and gasification of the transformer oil and the deterioration of the insulation; the reciprocating transition circuit of the on-load tap changer of the present invention, the switch element is explained by taking a single-break vacuum tube as an example, including a first main current switch MC1, a second main current switch MC2, a first vacuum tube V1, a second vacuum tube V2, a third vacuum tube V3, a fourth vacuum tube V4, a first transition resistor R1 and a second transition resistor R2; wherein one end of the first main current switch MC1 is connected to the first winding tap N of the transformer voltage regulating winding one end of the second main current-carrying switch MC2 is connected to the second winding tap N+1 of the transformer voltage regulating winding; one end of the first vacuum tube V1 is respectively connected to the first winding tap N of the transformer voltage regulating winding and the first main current-carrying switch MC1, and the other end is respectively connected to the second vacuum tube V2 and the first transition resistor R1; one end of the second vacuum tube V2 is respectively connected to the first vacuum tube V1 and the first transition resistor R1; one end of the third vacuum tube V3 is respectively connected to the second winding tap N+1 of the transformer voltage regulating winding and the second main current-carrying switch MC2, and the other end is respectively connected to the fourth vacuum tube V3 ... The empty tube V4 is connected to the second transition resistor R2; one end of the fourth vacuum tube V4 is respectively connected to the third vacuum tube V3 and the second transition resistor R2; one end of the first transition resistor R1 is respectively connected to the first vacuum tube V1 and the second vacuum tube V2; one end of the second transition resistor R2 is respectively connected to the third vacuum tube V3 and the fourth vacuum tube V4; the other ends of the first main current-passing switch MC1, the second main current-passing switch MC2, the second vacuum tube V2, the fourth vacuum tube V4, the first transition resistor R1 and the second transition resistor R2 are all connected to the neutral point lead-out terminal of the on-load tap changer.

[0055] In the embodiment of the present invention, when the first main flow switch MC1, the first vacuum tube V1, and the second vacuum tube V2 are all in the on state, and the second main flow switch MC2, the third vacuum tube V3, and the fourth vacuum tube V4 are all in the off state, the on-load tap changer transition circuit can make the load current flow out from the neutral point lead-out end through the first main flow switch MC1. When the second main flow switch MC2, the third vacuum tube V3, and the fourth vacuum tube V4 are all in the on state, and the first main flow switch MC1, the first vacuum tube V1, and the second vacuum tube V2 are all in the off state, the on-load tap changer transition circuit can make the load current flow out from the neutral point lead-out end through the second main flow switch MC2.

[0056] In the reciprocating switching process of the transition circuit of the on-load tap changer, the second vacuum tube V2 and the fourth vacuum tube V4 take turns to bear the task of breaking the load current, and the first vacuum tube V1 and the third vacuum tube V3 take turns to bear the task of breaking the inter-stage circulating current, thereby reducing the working loss of a single switching element, balancing the switching capacity between the switching elements, and reducing the failure rate of the switching elements; at the same time, since the transition circuit is completely composed of switching elements and transition resistors, there is no problem of arc extinction in the oil, which improves the reliability and electrical life of the on-load tap changer; in the process of forward and reverse reciprocating switching, the mechanical on-load tap changer adopting the transition circuit has a mirror-symmetric action sequence and does not require a mechanical track-changing mechanism.

[0057] A voltage regulation method for a reciprocating transition circuit of an on-load tap changer according to an embodiment of the present invention is described by taking a single-break vacuum tube as an example. When the on-load tap changer switches from the current transformer winding tap to the pre-selected new transformer winding tap, that is, from the first winding tap N to the second winding tap N+1, the switching process is as follows:

[0058] The first main current-passing switch MC1, the first vacuum tube V1, and the second vacuum tube V2 are all in the on state, and the second main current-passing switch MC2, the third vacuum tube V3, and the fourth vacuum tube V4 are all in the off state;

[0059] Disconnect the first main current-carrying switch MC1;

[0060] The second vacuum tube V2 is disconnected to generate an arc;

[0061] After the arc of the second vacuum tube V2 is completely extinguished, the third vacuum tube V3 is turned on;

[0062] Disconnect the first vacuum tube V1 to generate an arc;

[0063] After the first vacuum tube V1 is completely extinguished, the fourth vacuum tube V4 is turned on;

[0064] The second main current-passing switch MC2 is turned on, so that the load current I NThe current flows out from the second winding tap N+1 through the second main current-carrying switch MC2 from the neutral point, and the switching process of the on-load tap changer from the first winding tap N to the second winding tap N+1 is completed.

[0065] A voltage regulation method for a reciprocating transition circuit of an on-load tap changer according to an embodiment of the present invention is described by taking a single-break vacuum tube as an example. The switching process of the on-load tap changer from the second winding tap N+1 to the first winding tap N is as follows:

[0066] The second main current-passing switch MC2, the third vacuum tube V3, and the fourth vacuum tube V4 are all in the on state, and the first main current-passing switch MC1, the first vacuum tube V1, and the second vacuum tube V2 are all in the off state;

[0067] Disconnect the second main current-carrying switch MC2;

[0068] The fourth vacuum tube V4 is disconnected to generate an arc;

[0069] After the fourth vacuum tube V4 is completely extinguished, the first vacuum tube V1 is turned on;

[0070] The third vacuum tube V3 is disconnected to generate an arc;

[0071] After the arc of the third vacuum tube V3 is completely extinguished, the second vacuum tube V2 is turned on;

[0072] The first main current-passing switch MC1 is turned on, so that the load current I N The current flows out from the first winding tap N through the first main current-carrying switch MC1 from the neutral point, and the switching process of the on-load tap changer from the second winding tap N+1 to the first winding tap N is completed.

[0073] In the embodiment of the present invention, when the internal switch element in the reciprocating transition circuit of the on-load tap changer is a power electronic element with a controllable on-off function and a double-break vacuum tube, the action timing and voltage regulation method of the switch element are consistent and will not be described in detail.

[0074] A voltage regulation method for a reciprocating transition circuit of an on-load tap changer according to an embodiment of the present invention is described by taking a single-break vacuum tube as an example; when the on-load tap changer switches from winding tap N to winding tap N+1, the voltage regulation method is as follows:

[0075] like Figure 1 As shown, the first main current-carrying switch MC1, the first vacuum tube V1, and the second vacuum tube V2 are all in the on state, and the second main current-carrying switch MC2, the third vacuum tube V3, and the fourth vacuum tube V4 are all in the off state; the winding tap N is connected, and the load current flows out from the neutral point lead-out terminal through the first main current-carrying switch MC1.

[0076] like Figure 2As shown, the first main current-carrying switch MC1 is turned off, the second main current-carrying switch MC2 remains turned off, the first vacuum tube V1 and the second vacuum tube V2 remain turned on, and the third vacuum tube V3 and the fourth vacuum tube V4 remain turned off. The winding tap N continues to be turned on, and the load current flows out from the neutral point lead-out terminal through the first vacuum tube V1 and the second vacuum tube V2.

[0077] like Figure 3 As shown, the first main current-carrying switch MC1 remains off, the second main current-carrying switch MC2 remains off, the second vacuum tube V2 is disconnected, an arc is generated, the first vacuum tube V1 remains on, the third vacuum tube V3 and the fourth vacuum tube V4 remain off. The winding tap N continues to be connected, and the load current continues to flow out from the neutral point lead-out end through the first vacuum tube V1 and the first transition resistor R1.

[0078] like Figure 4 As shown, the first main current switch MC1 remains disconnected, the second main current switch MC2 remains disconnected, and after the arc in the second vacuum tube V2 is completely extinguished, the third vacuum tube V3 is turned on, the first vacuum tube V1 remains on, and the second vacuum tube V2 and the fourth vacuum tube V4 remain disconnected. The winding tap N and the winding tap N+1 are both connected, and the load current I N The current flows out from the neutral point through the first vacuum tube V1, the first transition resistor R1, the third vacuum tube V3, and the second transition resistor R2 respectively; the transition circuit forms a bridge connection to generate an inter-stage 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), said U S is the on-load tapchanger level voltage.

[0079] like Figure 5 As shown, the first main current-carrying switch MC1 remains disconnected, the second main current-carrying switch MC2 remains disconnected, the first vacuum tube V1 is disconnected, an arc is generated, the second vacuum tube V2 and the fourth vacuum tube V4 remain disconnected, and the third vacuum tube V3 remains turned on. The winding tap N+1 continues to be turned on, and the load current continues to flow out from the neutral point lead-out end through the third vacuum tube V3 and the second transition resistor R2.

[0080] like Figure 6As shown, the first main current-carrying switch MC1 remains disconnected, the second main current-carrying switch MC2 remains disconnected, and when the arc in the first vacuum tube V1 is completely extinguished, the fourth vacuum tube V4 is turned on, the first vacuum tube V1 and the second vacuum tube V2 remain disconnected, and the third vacuum tube V3 remains turned on. The winding tap N+1 continues to be connected, and the load current continues to flow out from the neutral point lead-out end through the third vacuum tube V3 and the fourth vacuum tube V4.

[0081] like Figure 7 As shown, the first main current-passing switch MC1 remains off, the second main current-passing switch MC2 is turned on, the first vacuum tube V1 and the second vacuum tube V2 remain off, the third vacuum tube V3 and the fourth vacuum tube V4 remain on. The winding tap N+1 continues to be connected, and the load current flows out from the neutral point lead-out terminal through the second main current-passing switch MC2.

[0082] When the on-load tap changer switches from winding tap N+1 to winding tap N, the switching process is symmetrical with the switching process of the on-load tap changer switching from winding tap N to winding tap N+1. The specific voltage regulation method is as follows:

[0083] The second main current-carrying switch MC2, the third vacuum tube V3, and the fourth vacuum tube V4 are all in the on state, and the first main current-carrying switch MC1, the first vacuum tube V1, and the second vacuum tube V2 are all in the off state; the winding tap N+1 is connected, and the load current flows out from the neutral point lead-out end through the second main current-carrying switch MC2.

[0084] The second main current-carrying switch MC2 is turned off, the first main current-carrying switch MC1 remains turned off, the first vacuum tube V1 and the second vacuum tube V2 remain turned off, and the third vacuum tube V3 and the fourth vacuum tube V4 remain turned on. The winding tap N+1 continues to be turned on, and the load current flows out from the neutral point lead-out end through the third vacuum tube V3 and the fourth vacuum tube V4.

[0085] The first main current-carrying switch MC1 remains off, the second main current-carrying switch MC2 remains off, the fourth vacuum tube V4 is turned off, an arc is generated, the third vacuum tube V3 remains on, the first vacuum tube V1 and the second vacuum tube V2 remain off. The winding tap N+1 continues to be connected, and the load current continues to flow out from the neutral point lead-out end through the third vacuum tube V3 and the second transition resistor R2.

[0086] The first main current switch MC1 remains off, the second main current switch MC2 remains off, and when the arc in the fourth vacuum tube V4 is completely extinguished, the first vacuum tube V1 is turned on, the third vacuum tube V3 is turned on, and the second vacuum tube V2 and the fourth vacuum tube V4 are turned off. The winding tap N and the winding tap N+1 are both turned on, and the load current I NThe current flows out from the neutral point through the first vacuum tube V1, the first transition resistor R1, the third vacuum tube V3, and the second transition resistor R2 respectively; the transition circuit forms a bridge connection to generate an inter-stage 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), said U S is the on-load tapchanger level voltage.

[0087] The first main current-carrying switch MC1 remains disconnected, the second main current-carrying switch MC2 remains disconnected, the third vacuum tube V3 is disconnected, an arc is generated, the second vacuum tube V2 and the fourth vacuum tube V4 remain disconnected, and the first vacuum tube V1 remains turned on. The winding tap N continues to be turned on, and the load current continues to flow out from the neutral point lead-out end through the first vacuum tube V1 and the first transition resistor R1.

[0088] The first main current-carrying switch MC1 remains disconnected, the second main current-carrying switch MC2 remains disconnected, and when the arc in the third vacuum tube V3 is completely extinguished, the second vacuum tube V2 is turned on, the third vacuum tube V3 and the fourth vacuum tube V4 remain disconnected, and the first vacuum tube V1 remains turned on. The winding tap N continues to be connected, and the load current continues to flow out from the neutral point lead-out end through the first vacuum tube V1 and the second vacuum tube V2.

[0089] The first main current-passing switch MC1 is turned on, the second main current-passing switch MC2 is kept off, the first vacuum tube V1 and the second vacuum tube V2 are kept on, the third vacuum tube V3 and the fourth vacuum tube V4 are kept off. The winding tap N continues to be connected, and the load current flows out from the neutral point lead-out terminal through the second main current-passing switch MC2.

[0090] When the internal switch element in the reciprocating transition circuit of the on-load tap changer is a power electronic element with controllable on-off function and a double-break vacuum tube, the action sequence and voltage regulation method of the switch element are consistent and will not be described in detail.

[0091] When the on-load tap changer switches from winding N tapping to winding N+1 tapping, the transition circuit conversion procedure diagram is as follows: Figure 8 As shown;

[0092] When the on-load tap changer switches from winding N+1 tapping to winding N tapping, the transition circuit conversion procedure diagram is as follows: Fig. 9 shown.

[0093] In the embodiment of the present invention, the switching tasks of the transition circuit of the on-load tap changer using a vacuum tube are shown in Table 1:

[0094] Table 1. Switching tasks

[0095]

[0096] Among them, I N is the load current; U S is the on-load tap changer level voltage; R1 and R2 are both transition resistors.

[0097] Fig.10 FIG. 1 is a circuit diagram of a reciprocating transition circuit of an on-load tap changer in which the switching element is a power electronic element according to an embodiment of the present invention, as shown in FIG. Fig.10 As shown, only Figure 1 The single-break vacuum tube in the system is replaced by a power electronic component with controllable on / off function. Figure 1 The components are the same, the action sequence is consistent, and the functions and effects are the same Figure 1 The transition circuits shown are the same and will not be described in detail.

[0098] Fig.11 FIG. 1 is a circuit diagram of a reciprocating transition circuit of an on-load tap changer whose switching element is a double-break vacuum tube according to an embodiment of the present invention; Fig.11 As shown, only Figure 1 The single-break vacuum tube in the system is replaced with a double-break vacuum tube, and the other components are the same as Figure 1 The components are the same, the action sequence is consistent, and the functions and effects are the same Figure 1 The transition circuits shown are the same and will not be described in detail.

[0099] In summary, the embodiment of the present invention provides a reciprocating transition circuit and voltage regulation method for an on-load tap changer. The transition circuit is completely composed of switch elements and transition resistors, and there is no problem of arc extinction in the oil. The second vacuum tube V2 and the fourth vacuum tube V4 take turns to take on the task of breaking the load current, and the first vacuum tube V1 and the third vacuum tube V3 take turns to take on the task of breaking the inter-stage circulating current, which reduces the working loss of a single switch element, balances the switching capacity between the switch elements, and reduces the failure rate of the switch elements. During the forward and reverse reciprocating switching process of the transition circuit, the action sequence is mirror-symmetrical, avoiding the mechanical structure track change operation. The transition circuit is designed with two transition resistors for current limiting, avoiding the problem of excessive temperature of the transition resistor due to concentrated heat generation of a single transition resistor, resulting in decomposition and gas production of transformer oil and insulation degradation.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A reciprocating transition circuit of an on-load tap changer, characterized in that: include: A first main pass-through switch, a second main pass-through switch, a first switching element, a second switching element, a third switching element, a fourth switching element, a first transition resistor, and a second transition resistor; The first end of the first main pass-through switch is connected to the first end of the first switch element, and both are used to be connected to the first winding tap N of the transformer voltage regulating winding; the first end of the second main pass-through switch is connected to the first end of the third switch element, and both are used to be connected to the second winding tap N+1 of the transformer voltage regulating winding; The second end of the first switch element, the first end of the second switch element, and the first end of the first transition resistor are connected; The second end of the third switch element, the first end of the fourth switch element, and the first end of the second transition resistor are connected; The second end of the first main pass-through switch, the second end of the second switch element, the second end of the first transition resistor, the second end of the second main pass-through switch, the second end of the fourth switch element, and the second end of the second transition resistor are all used to be connected to the neutral point lead-out terminal of the on-load tap changer; During the reciprocating switching process of the on-load tap changer transition circuit, the second switch element and the fourth switch element are used to take turns to break the load current; the first switch element and the third switch element are used to take turns to break the inter-stage circulating current; The first transition resistor and the second transition resistor are used to limit the inter-stage circulating current when the first winding tap N and the second winding tap N+1 of the transformer voltage regulating winding are bridged.

2. The on-load tap changer reciprocating transition circuit according to claim 1, characterized in that: The first switch element, the second switch element, the third switch element or the fourth switch element is a single-break vacuum tube, a double-break vacuum tube or a power electronic element with a controllable on-off function.

3. The on-load tap changer reciprocating transition circuit according to claim 1, characterized in that: It also includes: a transformer voltage regulating winding; The first end of the first main current-carrying switch and the first end of the first switching element are both connected to the first winding tap N of the transformer voltage regulating winding; The first end of the second main pass-through switch and the first end of the third switch element are both connected to the second winding tap N+1 of the transformer voltage regulating winding.

4. The on-load tap changer reciprocating transition circuit according to claim 1, characterized in that: Also includes: On-load tap-changer; The second end of the first main pass-through switch, the second end of the second switching element, the second end of the first transition resistor, the second end of the second main pass-through switch, the second end of the fourth switching element, and the second end of the second transition resistor are all connected to the neutral point lead-out terminal of the on-load tap changer.

5. A voltage regulating method for a reciprocating transition circuit of an on-load tap changer according to claim 1, characterized in that: The following steps are involved: The first main pass-through switch, the first switch element, and the second switch element are all in an on state; the second main pass-through switch, the third switch element, and the fourth switch element are all in an off state; Disconnecting the first main current-carrying switch; Turning off the second switch element and turning on the third switch element; Turning off the first switch element and turning on the fourth switch element; The second main current-carrying switch is turned on to allow the load current to flow out from the second winding tap N+1 through the second main current-carrying switch from the neutral point, and the switching process of the on-load tap changer from the first winding tap N to the second winding tap N+1 is completed.

6. A voltage regulating method for a reciprocating transition circuit of an on-load tap changer according to claim 1, characterized in that: The following steps are involved: The second main pass-through switch, the third switch element, and the fourth switch element are all in an on state; the first main pass-through switch, the first switch element, and the second switch element are all in an off state; Disconnecting the second main flow switch; Turning off the fourth switch element and turning on the first switch element; Turning off the third switch element and turning on the second switch element; The first main current-carrying switch is turned on to allow the load current to flow out from the neutral point through the first winding tap N via the first main current-carrying switch, and the switching process of the on-load tap changer from the second winding tap N+1 to the first winding tap N is completed.

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