Method and circuit for switching the tap of a load tap changer assisted by thyristors

Abstract

The application discloses a method and circuit for switching the position of a load tap changer assisted by a thyristor, and relates to the technical field of load tap changers of transformers, wherein the method comprises: switching the second contact from a first position to a second position based on the first position switching of the first contact, and disconnecting the third contact from the first position based on the second position switching of the first contact; and connecting the third contact disconnected from the first position to the second position based on the third position switching of the first contact. The technical scheme provided by the application can ensure the load tap changer to be uninterrupted during the position switching by using a freewheeling circuit. Through the time sequence cooperation of the thyristor circuit, the freewheeling circuit and the mechanical contact, the position switching of the main current circuit of the load tap changer can be realized by using only one set of thyristor circuit, and the position switching performance is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of on-load tap changers of transformers, in particular to a method and circuit for switching the position of an on-load tap changer assisted by thyristors. BACKGROUND

[0002] With the development of science and technology, power users have increasingly high requirements for voltage quality. In view of the voltage fluctuation problem in the power distribution process, a power distribution transformer with an on-load voltage regulation function is used to regulate the voltage level. The part of the power distribution transformer that realizes on-load voltage regulation is an on-load tap changer.

[0003] The existing on-load tap changer designed by using power electronics often uses more power electronic components to realize the structure design, and the switching performance of the position is poor when the position of the on-load tap changer is switched. SUMMARY

[0004] The application provides a method and circuit for switching the position of an on-load tap changer assisted by thyristors, which uses a group of thyristor circuits to assist the switching of the position of the on-load tap changer assisted by thyristors, has the effects of simple structure and low cost.

[0005] In a first aspect, the application provides a method for switching the position of an on-load tap changer assisted by thyristors, which is applied to a circuit for switching the position of an on-load tap changer assisted by thyristors. The circuit includes a thyristor circuit, a freewheeling circuit, a main current circuit, a voltage input end and a voltage output end. The thyristor circuit includes a first contact, the freewheeling circuit includes a second contact, the main current circuit includes a third contact, and the voltage input end includes a first position and a second position. One end of the thyristor circuit is connected to the first position of the voltage input end through the first contact, and the other end is connected to the freewheeling circuit. One end of the freewheeling circuit is connected to the first position of the voltage input end through the second contact, and the other end is connected to the voltage output end. One end of the main current circuit is connected to the first position of the voltage input end through the third contact, and the other end is connected to the voltage output end. The method includes:

[0006] Based on the first position switching of the first contact, the second contact is switched from the first position to the second position, and based on the second position switching of the first contact, the third contact is disconnected from the first position.

[0007] Based on the third position switching of the first contact, the third contact disconnected from the first position is connected to the second position.

[0008] By adopting the technical scheme, the use of the freewheeling circuit can ensure that the load-tap-changer is not powered off during gear switching, and through the timing cooperation of the thyristor circuit, the freewheeling circuit and the mechanical contact, the gear switching of the main current circuit of the load-tap-changer can be realized by using only one set of thyristor circuit, thereby reducing the complexity of gear switching.

[0009] Optionally, the first gear switching of the first contact includes:

[0010] disconnecting the first contact from the first gear and disconnecting the second contact from the first gear;

[0011] connecting the first contact to the second gear and connecting the second contact to the second gear;

[0012] switching the first contact from the second gear to the first gear and disconnecting the third contact from the first gear.

[0013] By adopting the technical scheme, the use of the freewheeling circuit can ensure that the load-tap-changer is not powered off during gear switching, and through the timing cooperation of the thyristor circuit, the freewheeling circuit and the mechanical contact, the gear switching of the main current circuit of the load-tap-changer can be realized by using only one set of thyristor circuit, thereby reducing the complexity of gear switching.

[0014] Optionally, the freewheeling circuit includes a freewheeling resistor and a changeover switch, a first fixed end of the changeover switch is connected with the first gear, a second fixed end of the changeover switch is connected with the voltage output end, an active end of the changeover switch is connected with the thyristor circuit, and the second fixed end of the changeover switch is connected with the active end of the changeover switch.

[0015] The disconnecting the first contact from the first gear and disconnecting the second contact from the first gear includes:

[0016] disconnecting the first contact from the first gear, disconnecting the active end of the changeover switch from the second fixed end, connecting the active end of the changeover switch with the first fixed end, and disconnecting the second contact from the first gear.

[0017] The switching the first contact from the second gear to the first gear and disconnecting the third contact from the first gear includes:

[0018] The first contact is disconnected from the second position, the movable terminal of the change-over switch is disconnected from the first fixed terminal and connected to the second fixed terminal, the first contact is connected to the first position, and the third contact is disconnected from the first position.

[0019] By using the above technical scheme, before the second contact is disconnected from the first position, the movable terminal of the change-over switch is switched from being connected to the second fixed terminal to being connected to the first fixed terminal, so that the first contact can be turned on when connected to the second position, and the pre-breakdown phenomenon of the second contact when connected to the second position is avoided; after the first contact is disconnected from the second position, the movable terminal of the change-over switch is switched from being connected to the first fixed terminal to being connected to the second fixed terminal, so that the first contact can be turned on between the first position and the voltage output terminal when connected to the first position, thereby reducing the arc time when the third contact is disconnected from the first position.

[0020] Optionally, the thyristor circuit comprises a bidirectional thyristor and an equivalent peripheral circuit, the first contact comprises a first loop contact and a first trigger contact, the first anode of the bidirectional thyristor is connected to the first loop contact, the second anode is connected to the freewheeling circuit, the control electrode is connected to one end of the equivalent peripheral circuit, and the other end of the equivalent peripheral circuit is connected to the first trigger contact.

[0021] The first contact is disconnected from the first position, which comprises:

[0022] The first trigger contact of the thyristor circuit is disconnected from the first position, and the first loop contact of the thyristor circuit is disconnected from the first position.

[0023] The first contact is connected to the second position, which comprises:

[0024] The first loop contact of the thyristor circuit is connected to the second position, and the first trigger contact of the thyristor circuit is connected to the second position.

[0025] The first contact is disconnected from the second position, which comprises:

[0026] The first trigger contact of the thyristor circuit is disconnected from the second position, and the first loop contact of the thyristor circuit is disconnected from the second position.

[0027] The first contact is connected to the first position, which comprises:

[0028] The first loop contact of the thyristor circuit is connected to the first position, and the first trigger contact of the thyristor circuit is connected to the first position.

[0029] By adopting the technical scheme, when the first contact is connected to a gear, the first loop contact is connected first and the first trigger contact is connected later, and when the first contact is disconnected from a gear, the first trigger contact is disconnected first and the first loop contact is disconnected later, so that damage to the bidirectional thyristor can be avoided.

[0030] Optionally, the third time gear switching of the first contact to connect the third contact disconnected from the first gear to the second gear comprises:

[0031] Switching the first contact from the first gear to the second gear and connecting the third contact disconnected from the first gear to the second gear.

[0032] By adopting the technical scheme, the second gear of the voltage input end and the voltage output end are connected by using the thyristor loop, so that the pre-breakdown phenomenon when the third contact is connected to the second gear can be avoided.

[0033] Optionally, the switching of the first contact from the first gear to the second gear and the connecting of the third contact disconnected from the first gear to the second gear comprises:

[0034] Disconnecting the first contact from the first gear, connecting the first contact to the second gear, and connecting the third contact disconnected from the first gear to the second gear.

[0035] By adopting the technical scheme, when the first contact is disconnected from a gear or connected to a gear, the on-off characteristics of the bidirectional thyristor in the thyristor loop are used to avoid the generation of arc, arc drawing and pre-breakdown phenomenon, which can cause damage to the element, and the pre-breakdown phenomenon when the main current loop is connected can be eliminated.

[0036] Optionally, the thyristor loop comprises a bidirectional thyristor and an equivalent peripheral circuit, the first contact comprises a first loop contact and a first trigger contact, the first anode of the bidirectional thyristor is connected to the first loop contact, the second anode is connected to the freewheeling loop, the control electrode is connected to one end of the equivalent peripheral circuit, and the other end is connected to the first trigger contact; the disconnecting of the first contact from the first gear comprises:

[0037] Disconnecting the first trigger contact of the thyristor loop from the first gear and disconnecting the first loop contact of the thyristor loop from the first gear;

[0038] The connecting of the first contact to the second gear comprises:

[0039] The first circuit contact of the thyristor circuit is connected to the second gear, and the first trigger contact of the thyristor circuit is connected to the second gear.

[0040] By adopting the above technical solutions, when the first contact is disconnected from the first gear and connected to the second gear, the first trigger contact connected to the control electrode follows the principle of first out and then in, that is, the first trigger contact is disconnected first when disconnected from the first gear, and the first trigger contact is connected later when connected to the second gear. According to the disconnection and connection of the first trigger contact connected to the control electrode, the conduction and cutoff of the bidirectional thyristor can be controlled, and the bidirectional thyristor can be prevented from being damaged.

[0041] In a second aspect, the application provides a load tap changer gear switching circuit assisted by thyristor arc extinction, the thyristor circuit further comprising a bidirectional thyristor, a protection capacitor, a protection resistor, a first trigger resistor, a second trigger resistor and a current limiting diode, the first contact comprising a first trigger contact and a first circuit contact;

[0042] One end of the protection capacitor is connected to the second anode of the bidirectional thyristor, and the other end is connected to one end of the protection resistor. The other end of the protection resistor is connected to the first anode of the bidirectional thyristor, and the first anode of the bidirectional thyristor is connected to the first circuit contact;

[0043] One end of the first trigger resistor is connected to the control electrode of the bidirectional thyristor, and the other end is connected to the negative electrode of the current limiting diode. The positive electrode of the current limiting diode is connected to the second anode of the bidirectional thyristor;

[0044] One end of the second trigger resistor is connected to the negative electrode of the current limiting diode, and the other end is connected to the first trigger contact.

[0045] In summary, one or more technical solutions provided in the embodiments of the application have at least the following technical effects or advantages:

[0046] By adopting the above technical solutions, the use of the freewheeling circuit can ensure that the load tap changer does not lose power during gear switching. Through the timing cooperation of the thyristor circuit, the freewheeling circuit and the mechanical contact, only one set of thyristor circuit can realize the gear switching of the main current circuit of the load tap changer, which has the effect of reducing the complexity of gear switching. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a structural schematic diagram of a load tap changer provided in the embodiments of the application;

[0048] Figure 2 is a structural schematic diagram of a load tap changer gear switching method assisted by thyristor arc extinction provided in the embodiments of the application;

[0049] Figure 3 is a flowchart of a step of switching a position of a load tap changer assisted by a thyristor according to an embodiment of the present application;

[0050] Figure 4 is a flowchart of a step of disconnecting a main current circuit according to an embodiment of the present application;

[0051] Figure 5 is a flowchart of a step of connecting a main current circuit according to an embodiment of the present application;

[0052] Figure 6 is a structural diagram of a load tap changer assisted by a thyristor according to an embodiment of the present application;

[0053] Figure 7 is a flowchart of a step of switching a position of a load tap changer assisted by a thyristor according to another embodiment of the present application;

[0054] Figure 8 is a flowchart of a step of disconnecting a first contact from a first position according to an embodiment of the present application;

[0055] Figure 9 is a structural diagram of a thyristor circuit according to an embodiment of the present application;

[0056] Figure 10 is a flowchart of a step of switching a position of a load tap changer assisted by a thyristor according to another embodiment of the present application;

[0057] Figure 11 is a flowchart of a step of connecting a first contact to a second position according to an embodiment of the present application;

[0058] Figure 12 is a flowchart of a step of disconnecting a first contact from a second position according to an embodiment of the present application;

[0059] Figure 13 is a flowchart of a step of switching a position of a load tap changer assisted by a thyristor according to another embodiment of the present application;

[0060] Figure 14 is a flowchart of a step of connecting a first contact to a first position according to an embodiment of the present application;

[0061] Figure 15 is a flowchart of a step of disconnecting a third contact from a first position according to an embodiment of the present application;

[0062] Figure 16 is a flowchart of a step of switching a position of a load tap changer assisted by a thyristor according to another embodiment of the present application;

[0063] Figure 17 is another step schematic diagram of disconnecting the first contact from the first gear provided by an embodiment of the present application;

[0064] Figure 18 is another step schematic diagram of connecting the first contact to the second gear provided by an embodiment of the present application;

[0065] Figure 19 is a step schematic diagram of connecting the third contact to the second gear provided by an embodiment of the present application. The label explanation: R, protection resistance; C, protection capacitor; TR1, first trigger resistance; TR2, second trigger resistance; TVS, current limiting diode; KT, first trigger contact; K, first return contact; T, bidirectional thyristor; XR, freewheeling resistance; S, switching switch; S1, first fixed end; S2, second fixed end; O, voltage output end; J, second contact; M, third contact. DETAILED DESCRIPTION

[0066] In order for those skilled in the art to better understand the technical solutions in the specification, the technical solutions in the specification will be clearly and completely described below in combination with the drawings in the specification. Obviously, the described embodiments are only some of the embodiments of the present application, not all.

[0067] In the description of the embodiments of the present application, the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. The terms "include", "contain", "have" and their variants mean "include but are not limited to", unless otherwise specifically emphasized.

[0068] Before introducing the embodiments of the present application, first, some terms involved in the embodiments of the present application are defined and explained. The technical solutions provided by the present application can be applied to the scene of on-load tap changer of transformer, please see Figure 1 is a structural schematic diagram of an on-load tap changer provided by the present application.

[0069] The on-load tap changer (OLTC) of transformer refers to a kind of voltage regulating device for changing the connection position of transformer winding tap, which is suitable for operating under transformer excitation or load. Its basic principle is to realize the switching between taps in transformer winding under the condition of ensuring no interruption of load current, so as to change the number of turns of winding, i.e. the voltage ratio of transformer, and finally realize the purpose of voltage regulation.

[0070] Please see Figure 2 ,Figure 2 A structure schematic diagram of a thyristor-assisted arc extinguishing on-load tap changer gear switching circuit is provided in the embodiment of the present application. The thyristor-assisted arc extinguishing on-load tap changer gear switching circuit comprises a thyristor loop, a freewheeling loop, a main current-carrying loop, a voltage input end, and a voltage output end. The thyristor loop comprises a first contact, the freewheeling loop comprises a second contact, the main current-carrying loop comprises a third contact, and the voltage input end comprises a first gear and a second gear. One end of the thyristor loop is connected to the first gear of the voltage input end via the first contact, and the other end is connected to the freewheeling loop. One end of the freewheeling loop is connected to the first gear of the voltage input end via the second contact, and the other end is connected to the voltage output end. One end of the main current-carrying loop is connected to the first gear of the voltage input end via the third contact, and the other end is connected to the voltage output end.

[0071] Please refer to Figure 3 , Figure 3 A flowchart of an on-load tap changer is provided in the embodiment of the present application. The embodiment of the present application is based on a thyristor-assisted arc extinguishing on-load tap changer gear switching circuit, and takes the target of performing gear switching as the theme to make a detailed description of the specific steps of the thyristor-assisted arc extinguishing on-load tap changer gear switching method.

[0072] In S101, based on the first gear switching of the first contact, the second contact is switched from the first gear to the second gear, and based on the second gear switching of the first contact, the third contact is disconnected from the first gear.

[0073] The thyristor loop is a loop containing a bidirectional thyristor element, which does not need to provide a trigger signal through an external circuit to trigger the bidirectional thyristor, can realize passive triggering in the first gear switching and the second gear switching, and can reduce the structural complexity.

[0074] The freewheeling loop can maintain the conduction of the load current when the on-load tap changer gear switching is performed.

[0075] The main current-carrying loop is a main loop for supplying power to the load when the transformer is running, and is also the target loop of the gear adjustment of the on-load tap changer in the embodiment of the present application, i.e., it is necessary to realize the switching of the main current-carrying loop from the first gear to the second gear.

[0076] It should be understood that the first gear and the second gear in the embodiment of the present application are only used to facilitate the switching between two gears of the on-load tap changer, and are not limited to only two gears of the on-load tap changer. The switching between multiple gears can be completed according to the method steps provided in the embodiment of the present application.

[0077] It should be understood that the first contact, the second contact, and the third contact include but are not limited to mechanical contacts to achieve the purpose of disconnection and connection required by the embodiment of the present application.

[0078] Please refer to Figure 4 , the step schematic diagram of the main current-carrying circuit disconnection provided for the embodiment of the application.

[0079] Firstly, the first contact is switched from the first gear to the second gear through the first gear switching of the first contact, and the conduction of the freewheeling circuit in the second gear ensures that the load after the voltage output end is not powered off when the main current-carrying circuit is disconnected from the first gear. Then, based on the second gear switching of the thyristor circuit, the third contact is disconnected from the first gear, and due to the conduction characteristics of the thyristor circuit, the thyristor circuit will not produce arc and pre-breakdown phenomenon during switching. Therefore, when the third contact is disconnected from the first gear, the thyristor circuit will conduct the first gear and the voltage output end, which can reduce the arc duration when the third contact is disconnected.

[0080] S102, based on the third gear switching of the first contact, the third contact disconnected from the first gear is connected to the second gear.

[0081] Please refer to Figure 5 , the step schematic diagram of the main current-carrying circuit disconnection provided for the embodiment of the application.

[0082] If the third contact is directly connected to the second gear, the main current-carrying circuit will short-circuit the freewheeling circuit, thereby causing overvoltage at the moment of connection, which will harm the electrical equipment related to the transformer. Based on the conduction characteristics of the thyristor circuit, the third gear of the main current-carrying circuit is connected to the second gear in advance, so that the third gear of the main current-carrying circuit can be connected to the same potential.

[0083] Please refer to Figure 6 , the structure schematic diagram of the on-load tap changer with thyristor auxiliary arc extinction provided for the embodiment of the application, wherein the first trigger contact KT is connected to the equivalent peripheral circuit, the first circuit contact K is connected to the bidirectional thyristor T, the second contact J is connected to the freewheeling resistor XR, the first fixed end S1 of the switching switch S is connected to the second contact J, the second fixed end S2 is connected to the voltage output end O, and the third contact M is connected to the voltage output end O. The application provides a method for switching the gears of the on-load tap changer with thyristor auxiliary arc extinction, and the method steps for disconnecting the main current-carrying circuit from the first gear are described in detail, please refer to Figure 7 , the flowchart schematic diagram of another method for switching the gears of the on-load tap changer with thyristor auxiliary arc extinction provided for the embodiment of the application, the specific steps are S201 to S204, and the above steps include:

[0084] Step S201, disconnect the first contact from the first gear and disconnect the second contact from the first gear.

[0085] S2011, disconnect the first contact from the first gear.

[0086] In one embodiment of the present application, the thyristor circuit comprises a bidirectional thyristor T and an equivalent peripheral circuit, the first contact comprises a first circuit contact K and a first trigger contact KT, the first anode of the bidirectional thyristor T is connected with the first circuit contact K, the second anode is connected with a freewheeling circuit, the control electrode is connected with one end of the equivalent peripheral circuit, and the other end of the equivalent peripheral circuit is connected with the first trigger contact KT.

[0087] The specific steps for disconnecting the first contact from the first gear in the embodiment of the present application are: disconnecting the first trigger contact KT of the thyristor circuit from the first gear, and disconnecting the first circuit contact K of the thyristor circuit from the first gear.

[0088] Please refer to Figure 8 The step diagram for disconnecting the first contact from the first gear provided in the embodiment of the present application is the specific step for disconnecting the first contact from the first gear, which follows the principle that the control electrode is disconnected first and the first anode is disconnected later. Due to the existence of the equivalent peripheral circuit, the current is small when the first trigger contact KT is disconnected from the first gear, and no arc is generated. After the first trigger contact KT is disconnected, the thyristor circuit is immediately cut off, and then it is relatively safe to disconnect the first circuit contact K from the first gear. If the first circuit contact K is disconnected first, the thyristor circuit is in the conducting state, and then arc may damage other components.

[0089] Please refer to Figure 9 The structure diagram of the thyristor circuit provided in the embodiment of the present application further comprises a bidirectional thyristor T, a protection capacitor C, a protection resistor R, a first trigger resistor TR1, a second trigger resistor TR2, and a current-limiting diode TVS. The first contact comprises a first trigger contact KT and a first circuit contact K.

[0090] One end of the protection capacitor C is connected with the second anode of the bidirectional thyristor T, the other end is connected with one end of the protection resistor R, the other end of the protection resistor R is connected with the first anode of the bidirectional thyristor T, and the first anode of the bidirectional thyristor T is connected with the first circuit contact K.

[0091] One end of the first trigger resistor TR1 is connected with the control electrode of the bidirectional thyristor T, the other end is connected with the negative electrode of the current-limiting diode TVS, and the positive electrode of the current-limiting diode is connected with the second anode of the bidirectional thyristor T.

[0092] One end of the second trigger resistor TR2 is connected with the negative pole of the current-limiting diode TVS, and the other end is connected with the first trigger contact KT.

[0093] It should be understood that the structure circuit of the thyristor circuit provided by the present application is an exemplary bidirectional thyristor peripheral circuit, the current-limiting diode is a transient voltage suppression diode, and the conduction condition of the bidirectional thyristor T is that there is a voltage difference between the first anode and the second anode, and a certain trigger current flows into the control electrode. In the present application, the first trigger contact KT connected with the control electrode and the first circuit contact K connected with the first anode are simultaneously connected with the first gear or the second gear. Therefore, in order to achieve the passive conduction condition of the bidirectional thyristor T, an equivalent peripheral circuit is arranged between the bidirectional thyristor T and the voltage input end.

[0094] S2012, disconnecting the movable end of the switch from the second fixed end, and connecting the movable end of the switch with the first fixed end.

[0095] In one embodiment of the present application, the freewheeling circuit comprises a freewheeling resistor XR and a switch S. The first fixed end S1 of the switch S is connected with the first gear, the second fixed end S2 of the switch S is connected with the voltage output end O, the movable end of the switch S is connected with the thyristor circuit, and the second fixed end S2 of the switch S is connected with the movable end of the switch S.

[0096] Please refer to Figure 10 A step diagram of the action of the switch S provided by the embodiment of the present application is shown. After the first contact is disconnected from the first gear, if the action of the switch S is not performed, when the first contact is connected to the second gear, the voltage level of the two ends of the thyristor circuit is the same, and the thyristor circuit cannot be turned on. When the second contact J is connected to the second gear, it is equivalent to connecting to the live line, and the pre-breakdown phenomenon will occur. The switch S is used to connect the freewheeling resistor XR and the thyristor circuit in series. The freewheeling resistor XR plays a role of voltage division at this time, and forms the conduction condition of the thyristor circuit, so that the freewheeling circuit can be safely connected.

[0097] For example, the switch S in the embodiment of the present application includes but is not limited to a single-pole double-throw switch. The movable end of the switch S corresponds to the movable blade of the single-pole double-throw switch, and the first fixed end S1 and the second fixed end S2 correspond to two contact points of the single-pole double-throw switch, respectively.

[0098] S2013, disconnecting the second contact from the first gear.

[0099] The main current-carrying circuit connected with the first gear and the voltage output end O is equivalent to short-circuiting the freewheeling circuit. Therefore, when the second contact J is disconnected from the first gear, no arc will be generated due to the absence of current.

[0100] Step S202, connecting the first contact to the second gear, and connecting the second contact to the second gear.

[0101] After disconnecting the first contact from the first gear and disconnecting the second contact J from the first gear, the first contact is connected to the second gear first, and then the second contact J is connected to the second gear.

[0102] In one embodiment, the step of connecting the first contact to the second gear further comprises:

[0103] The first loop contact K of the thyristor loop is connected to the second gear, and the first trigger contact KT of the thyristor loop is connected to the second gear.

[0104] Please refer to Figure 11 A schematic diagram of the step of connecting the first contact to the second gear is provided for the embodiment of the application. The principle of connecting the first loop contact K of the thyristor loop first and then connecting the first trigger contact KT is followed. The first loop contact K is connected to the first anode of the bidirectional thyristor T, and the first trigger contact KT is connected to the control electrode of the bidirectional thyristor T through the equivalent peripheral circuit. The first loop contact K is connected to the second gear first, and the control electrode of the bidirectional thyristor T is in the disconnected state, i.e. the thyristor loop is in the cut-off state, and the first loop contact K will not appear pre-breakdown phenomenon. At the same time, the first trigger contact KT is connected to the second gear, and due to the voltage division effect of the equivalent peripheral circuit, the access current is small, and at the same time the first trigger contact KT turns on the thyristor loop at the moment of access, and a large current is output through the freewheeling resistor XR, so it is safer.

[0105] Step S203, switching the first contact from the second gear to the first gear, and disconnecting the third contact from the first gear.

[0106] S2031, disconnecting the first contact from the second gear.

[0107] In one embodiment, the first trigger contact KT of the thyristor loop is disconnected from the second gear, and the first loop contact K of the thyristor loop is disconnected from the second gear.

[0108] Please refer to Figure 12 A schematic diagram of the step of disconnecting the first contact from the second gear is provided for the embodiment of the application. The specific steps of disconnecting the first contact from the second gear are similar to the principle of disconnecting the first contact from the first gear, which has been described in detail in the above embodiment, and will not be repeated here.

[0109] S2032, disconnecting the movable end of the switching switch from the first fixed end, and connecting the movable end of the switching switch to the second fixed end.

[0110] Please refer to Figure 13Another step diagram of switching operation provided by the embodiment of the present application.

[0111] If the connection between the movable terminal of the switch and the first fixed terminal S1 is not disconnected, when the first contact is connected to the first gear, the first gear and the second gear are conducted through the thyristor loop, resulting in short circuit between the two gears of the transformer tap changer, and part of the windings of the transformer is short-circuited, resulting in voltage change on the low-voltage side.

[0112] S2033, the first contact is connected to the first gear.

[0113] In one embodiment, the first loop contact K of the thyristor loop is connected to the first gear, and the first trigger contact KT of the thyristor loop is connected to the first gear.

[0114] Please refer to Figure 14 A step diagram of connecting the first contact to the first gear provided by the embodiment of the present application. The specific steps of connecting the first contact to the first gear are similar to the principle of disconnecting the first contact from the second gear, which has been described in detail in the above embodiment and will not be repeated here.

[0115] S2034, the third contact is disconnected from the first gear.

[0116] Please refer to Figure 15 A step diagram of disconnecting the third contact from the first gear provided by the embodiment of the present application. When the third contact M is still connected to the first gear, the voltage level at both ends of the thyristor loop is the same, and the thyristor loop is in the off state; at the moment when the third contact M is disconnected from the first gear, the main current loop appears arc, at the same time, the voltage of the second anode of the thyristor loop changes, the thyristor loop is momentarily conducted, the current of the voltage input end is conducted to the voltage output end O through the thyristor loop, so that the arc disappears, therefore, the arc duration is very short, it needs to be understood that the arc moment of generating high voltage and the moment when the main current loop is completely disconnected can make the thyristor loop conduct, which can keep the power supply during switching.

[0117] Step S204, based on the third gear switching of the first contact, the third contact disconnected from the first gear is connected to the second gear.

[0118] After the third contact M is disconnected from the first gear, the third contact M is connected to the second gear with the assistance of the thyristor loop, and the gear switching of the main current loop is completed.

[0119] The present application provides a thyristor-assisted arc-extinguishing on-load tap changer gear switching method, and the method steps of connecting the main current loop to the second gear are introduced in detail, please refer to Figure 16Another flowchart of the step of switching the position of the load tap changer assisted by the thyristor auxiliary arc extinguishing is provided in the embodiment of the present application, and the specific steps are S301 to S303, and the above steps include:

[0120] S301, based on the first position switching of the first contact, switching the second contact from the first position to the second position, and based on the second position switching of the first contact, disconnecting the third contact from the first position.

[0121] The step of disconnecting the third contact M from the first position has been described in detail in the steps S201 to S203, and will not be repeated here.

[0122] S302, switching the first contact from the first position to the second position.

[0123] S3021, disconnecting the first contact from the first position.

[0124] In an embodiment of the present application, the first trigger contact KT of the thyristor circuit is disconnected from the first position, and the first circuit contact K of the thyristor circuit is disconnected from the first position.

[0125] Please refer to Figure 17 The step of disconnecting the first contact from the first position provided in another embodiment of the present application is shown in the figure, because the thyristor circuit is in the on state, the first trigger contact KT must be disconnected from the first position first, the thyristor circuit is cut off, and then the first circuit contact K of the thyristor circuit is disconnected from the first position, so as to complete the disconnection of the thyristor circuit.

[0126] S3022, connecting the first contact to the second position.

[0127] In an embodiment of the present application, the first circuit contact K of the thyristor circuit is connected to the second position, and the first trigger contact KT of the thyristor circuit is connected to the second position.

[0128] Please refer to Figure 18 The step of connecting the first contact to the second position provided in another embodiment of the present application is shown in the figure, if the first trigger contact KT is connected to the second position first, the voltage difference between the first anode and the second anode of the bidirectional thyristor T is divided by the freewheeling resistor XR at the moment of connecting the first circuit contact K to the second position, so that the thyristor circuit is momentarily turned on, the on position is the first circuit contact K, and the pre-breakdown phenomenon may occur; and if the first circuit contact K is connected to the second position first, the thyristor circuit is in the off state, the line of the control electrode is not the main circuit of the current at the moment of connecting the first trigger contact KT to the second position, the current is small, and the on position is the bidirectional thyristor T, so that the pre-breakdown phenomenon can be avoided.

[0129] S303, the third contact of the first gear is connected to the second gear.

[0130] Please see Figure 19 A third contact access to the second gear step schematic diagram provided for the embodiment of the application, before the main current circuit is connected to the second gear, the second gear is conducted with the voltage output end O through the thyristor circuit, the second gear and the third contact M are equipotential, so the third contact M will not produce pre-breakdown phenomenon when access to the second gear, at the same time, the thyristor circuit and the freewheeling circuit are short-circuited by the main current circuit, return to the initial state when connected to the first gear, facilitate subsequent switching to other gear operation.

[0131] Through the above technical scheme, using the freewheeling circuit can ensure that the on-load tap changer is not powered off when switching gears, through the timing cooperation of the thyristor circuit, the freewheeling circuit and the mechanical contact, only one set of thyristor circuit can realize the gear switching of the main current circuit of the on-load tap changer, which has the effect of reducing the complexity of gear switching.

Claims

1. A method for switching the tap position of an on-load tap changer with thyristor-assisted arc extinguishing, characterized in that, A tap changer switching circuit for thyristor-assisted arc extinguishing includes a thyristor circuit, a freewheeling circuit, a main current-carrying circuit, a voltage input terminal, and a voltage output terminal. The thyristor circuit includes a first contact, the freewheeling circuit includes a second contact, and the main current-carrying circuit includes a third contact. The voltage input terminal includes a first tap position and a second tap position. One end of the thyristor circuit is connected to the first tap position of the voltage input terminal via the first contact, and the other end is connected to the freewheeling circuit. One end of the freewheeling circuit is connected to the first tap position of the voltage input terminal via the second contact, and the other end is connected to the voltage output terminal. One end of the main current-carrying circuit is connected to the first tap position of the voltage input terminal via the third contact, and the other end is connected to the voltage output terminal. The method includes: Based on the first position switching of the first contact, the second contact is switched from the first position to the second position; based on the second position switching of the first contact, the third contact is disconnected from the first position. Based on the third gear switch of the first contact, the third contact, which was disconnected from the first gear, is connected to the second gear.

2. The method according to claim 1, characterized in that, The first gear switching based on the first contact, switching the second contact from the first gear to the second gear, and the second gear switching based on the first contact, disconnecting the third contact from the first gear, includes: Disconnect the first contact from the first position, and disconnect the second contact from the first position; Connect the first contact to the second position, and connect the second contact to the second position; Switch the first contact from the second position to the first position, and disconnect the third contact from the first position.

3. The method according to claim 2, characterized in that, The freewheeling circuit includes a freewheeling resistor and a changeover switch. The first fixed terminal of the changeover switch is connected to the first gear position, the second fixed terminal of the changeover switch is connected to the voltage output terminal, the movable terminal of the changeover switch is connected to the thyristor circuit, and the second fixed terminal of the changeover switch is connected to the movable terminal of the changeover switch. Disconnecting the first contact from the first position and disconnecting the second contact from the first position includes: Disconnect the first contact from the first position, disconnect the connection between the movable end of the changeover switch and the second fixed end, connect the movable end of the changeover switch to the first fixed end, and disconnect the second contact from the first position. Switching the first contact from the second position to the first position and disconnecting the third contact from the first position includes: Disconnect the first contact from the second position, disconnect the movable end of the changeover switch from the first fixed end, connect the movable end of the changeover switch to the second fixed end, connect the first contact to the first position, and disconnect the third contact from the first position.

4. The method according to claim 3, characterized in that, The thyristor circuit includes a bidirectional thyristor and an equivalent peripheral circuit. The first contact includes a first circuit contact and a first trigger contact. The first anode of the bidirectional thyristor is connected to the first circuit contact, the second anode is connected to the freewheeling circuit, the control electrode is connected to one end of the equivalent peripheral circuit, and the other end of the equivalent peripheral circuit is connected to the first trigger contact. Disconnecting the first contact from the first position includes: Disconnect the first trigger contact of the thyristor circuit from the first position, and disconnect the first circuit contact of the thyristor circuit from the first position; Connecting the first contact to the second position includes: Connect the first circuit contact of the thyristor circuit to the second position, and connect the first trigger contact of the thyristor circuit to the second position; Disconnecting the first contact from the second position includes: Disconnect the first trigger contact of the thyristor circuit from the second position, and disconnect the first circuit contact of the thyristor circuit from the second position; Connecting the first contact to the first gear position includes: Connect the first circuit contact of the thyristor circuit to the first gear position, and connect the first trigger contact of the thyristor circuit to the first gear position.

5. The method according to claim 1, characterized in that, The third gear switching based on the first contact, which connects the third contact, which is disconnected from the first gear, to the second gear, includes: Switch the first contact from the first gear position to the second gear position, and connect the third contact, which was disconnected from the first gear position, to the second gear position.

6. The method according to claim 5, characterized in that, The step of switching the first contact from the first position to the second position and connecting the third contact, which was disconnected from the first position, to the second position includes: Disconnect the first contact from the first gear position, connect the first contact to the second gear position, and connect the third contact that was disconnected from the first gear position to the second gear position.

7. The method according to claim 6, characterized in that, The thyristor circuit includes a bidirectional thyristor and an equivalent peripheral circuit. The first contact includes a first circuit contact and a first trigger contact. The first anode of the bidirectional thyristor is connected to the first circuit contact, the second anode is connected to the freewheeling circuit, the control electrode is connected to one end of the equivalent peripheral circuit, and the other end of the equivalent peripheral circuit is connected to the first trigger contact. Disconnecting the first contact from the first position and connecting the first contact to the second position includes: Disconnect the first trigger contact of the thyristor circuit from the first position, and disconnect the first circuit contact of the thyristor circuit from the first position; Connect the first circuit contact of the thyristor circuit to the second position, and connect the first trigger contact of the thyristor circuit to the second position.

8. The method according to claim 1, characterized in that, The thyristor circuit also includes a bidirectional thyristor, a protection capacitor, a protection resistor, a first trigger resistor, a second trigger resistor, and a current-limiting diode. The first contact includes a first trigger contact and a first circuit contact. One end of the protection capacitor is connected to the second anode of the bidirectional thyristor, and the other end is connected to one end of the protection resistor. The other end of the protection resistor is connected to the first anode of the bidirectional thyristor, and the first anode of the bidirectional thyristor is connected to the first circuit contact. One end of the first trigger resistor is connected to the control electrode of the bidirectional thyristor, and the other end is connected to the negative electrode of the current-limiting diode. The positive electrode of the current-limiting diode is connected to the second anode of the bidirectional thyristor. One end of the second trigger resistor is connected to the negative terminal of the current-limiting diode, and the other end is connected to the first trigger contact.

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