On-load tap changer for high-voltage transmission transformer and control method thereof

Abstract

The present invention provides an on-load tap changer for a high-voltage transmission transformer and a control method thereof. The on-load tap changer comprises a tap selector and a power electronic switching switch; the power electronic switching switch comprises a mechanical switch assembly, a power electronic switch assembly and an insulating sleeve; the mechanical switch assembly is connected to a high-voltage transmission transformer winding tap via the tap selector, and the tap selector and the mechanical switch assembly are both located inside the high-voltage transmission transformer, while the power electronic switch assembly (4) is located outside the high-voltage transmission transformer; the mechanical switch assembly can achieve arc-free closing and shutoff, and has high safety; the power electronic switch assembly does not need to withstand voltage stress for a long time during steady-state operation, can withstand lightning strikes, and is not prone to breakdown failure; the use of fully controlled power devices can shorten the time delay caused by the thyristor turning off by current zero crossing, thereby improving the switching speed, reducing the heat generation of the current limiting resistor, and extending the life of the on-load tap changer.

Description

Technical Field

[0001] The present invention relates to the technical field of transformers, and in particular to an on-load tap changer for a high-voltage transmission transformer and a control method thereof. Background Art

[0002] On-load tap changers (OLTCs) are the core components of power transformers for voltage regulation. OLTC technology is a crucial means of voltage stabilization. Without interrupting power, the OLTC switches the transformer from one tap to another, adjusting the number of effective turns in the transformer windings to achieve voltage regulation. Currently, over 90% of power transformers in China, ranging from 10 to 500 kV, are equipped with OLTCs, all of which are mechanical. Mechanical OLTCs have numerous moving parts and long switching times. If the timing error between adjacent mechanical switches exceeds a preset value, arc extinguishing becomes difficult, causing arc discharges exceeding hundreds of kiloamperes in the OLTC, which can easily lead to explosions and fires. To address these issues with mechanical OLTCs, replacing them with power electronics has become a research hotspot, with hybrid mechanical-power-electronic OLTCs being the preferred approach. During the switching process of a mechanical-power-electronic hybrid on-load tap-changer, the mechanical switch has to withstand a large voltage to close or shut down. The arc generated by the mechanical switch may cause the transformer to catch fire or even explode, resulting in poor safety. In addition, power electronic devices generally use thyristors, which have a long switching time. In addition, power electronic devices need to withstand voltage stress for a long time during steady-state operation, which makes them prone to breakdown and failure. In addition, a large number of semi-controlled power electronic devices need to be connected in series, resulting in high cost. Summary of the Invention

[0003] In order to overcome the shortcomings of poor safety in the above-mentioned prior art, the present invention provides an on-load tap changer for a high-voltage transmission transformer, comprising a tap selector (1) and a power electronic switch (2); the power electronic switch (2) comprises a mechanical switch assembly (3), a power electronic switch assembly (4) and an insulating bushing;

[0004] The mechanical switch assembly (3) is connected to a high-voltage transmission transformer winding tap via a tap selector (1), the mechanical switch assembly (3) is connected to a power electronic switch assembly (4) via an insulating bushing, and both the mechanical switch assembly (3) and the power electronic switch assembly (4) are connected to a neutral point of an on-load tap changer, the tap selector (1) and the mechanical switch assembly (3) are both located inside the high-voltage transmission transformer, and the power electronic switch assembly (4) is located outside the high-voltage transmission transformer.

[0005] The mechanical switch assembly (3) comprises a first mechanical switch (100), a second mechanical switch (200), a third mechanical switch (300), a fourth mechanical switch (400) and a fifth mechanical switch (500);

[0006] The first mechanical switch (100) and the third mechanical switch (300) are both connected to one end of the tap selector (1), the second mechanical switch (200) and the fourth mechanical switch (400) are both connected to the other end of the tap selector (1), and the fifth mechanical switch (500) has one end connected to the third mechanical switch (300) and the fourth mechanical switch (400), and the other end connected to the neutral point of the on-load tap changer.

[0007] The power electronic switch assembly (4) comprises a first power electronic switch (701) and a second power electronic switch (702);

[0008] One end of the first power electronic switch (701) is connected to the first mechanical switch (100) and the second mechanical switch (200), and the other end is connected to the neutral point of the on-load tap changer;

[0009] One end of the second power electronic switch (702) is connected to the third mechanical switch (300) and the fourth mechanical switch (400), and the other end is connected to the neutral point of the on-load tap changer.

[0010] The power electronic switching switch (2) further comprises a current limiting resistor (600), wherein the current limiting resistor (600) is located inside the high-voltage transmission transformer;

[0011] One end of the current limiting resistor (600) is connected to the first mechanical switch (100) and the second mechanical switch (200), and the other end is connected to the first power electronic switch (701).

[0012] The insulating sleeve comprises a first insulating sleeve (801), a second insulating sleeve (802) and a third insulating sleeve (803);

[0013] The first insulating sleeve (801) is located between the current limiting resistor (600) and the first power electronic switch (701);

[0014] The second insulating sleeve (802) is located between the third mechanical switch (300), the fourth mechanical switch (400) and the second power electronic switch (702);

[0015] The third insulating sleeve (803) is located at the neutral point of the third mechanical switch (300) and the fourth mechanical switch (400) and is connected to the on-load tap changer.

[0016] The first power electronic switch (701) and the second power electronic switch (702) both include a first bridge circuit and a fully controlled power device;

[0017] The first bridge circuit includes four diodes; two of the diodes are connected in series in the same direction to form a first half-bridge, and the remaining two diodes are connected in series in the same direction to form a second half-bridge. The first half-bridge and the second half-bridge are connected in parallel, and the fully-controlled power device is connected in parallel between the first half-bridge and the second half-bridge.

[0018] The first power electronic switch (701) and the second power electronic switch (702) both include a second bridge circuit and a DC capacitor;

[0019] The second bridge circuit includes four IGBT modules; two of the IGBT modules are connected in series in the same direction to form a third half-bridge, and the remaining two IGBT modules are connected in series in the same direction to form a fourth half-bridge. The third half-bridge and the fourth half-bridge are connected in parallel, and the DC capacitor is connected in parallel between the third half-bridge and the fourth half-bridge.

[0020] The first power electronic switch (701) and the second power electronic switch (702) each comprise a plurality of IGBT components connected in series;

[0021] Each IGBT assembly consists of two IGBT modules connected in series.

[0022] The fully controlled power device includes an IGBT or an IGCT.

[0023] The IGBT module includes an IGBT and a diode connected in anti-parallel with the IGBT.

[0024] On the other hand, the present invention also provides a control method for an on-load tap changer of a high-voltage transmission transformer, comprising:

[0025] Before the on-load tap changer is switched, the mechanical switch assembly (3) of the power electronic switch (2) is controlled to make the current flow through the high-voltage transmission transformer winding, one end of the tap selector (1), the mechanical switch assembly (3), the insulating bushing and the neutral point of the on-load tap changer in sequence;

[0026] During the on-load tap changer switching, the state of the mechanical switch component (3) is adjusted and the power electronic switch component (4) of the power electronic switch (2) is triggered at the same time, so that the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector (1), the mechanical switch component (3), the insulating bushing and the neutral point of the on-load tap changer.

[0027] The method of controlling the mechanical switch assembly (3) of the power electronic switch (2) before the on-load tap changer is switched so that current flows sequentially through the winding of the high-voltage transmission transformer, one end of the tap selector (1), the mechanical switch assembly (3) and the neutral point of the on-load tap changer comprises:

[0028] The first mechanical switch (100), the third mechanical switch (300) and the fifth mechanical switch (500) of the mechanical switch assembly (3) are controlled to be closed, and the second mechanical switch (200) and the fourth mechanical switch (400) of the mechanical switch assembly (3) are controlled to be opened, so that the current flows sequentially through the high-voltage transmission transformer winding, one end of the tap selector (1), the third mechanical switch (300), the fifth mechanical switch (500), the third insulating bushing (803) of the insulating bushing and the neutral point of the on-load tap changer.

[0029] The method comprises adjusting the state of the mechanical switch assembly (3) and triggering the power electronic switch assembly (4) of the power electronic switch (2) during the switching of the on-load tap changer, so that the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector (1), the mechanical switch assembly (3) and the neutral point of the on-load tap changer, including:

[0030] The first mechanical switch (100) is controlled to be disconnected, the second mechanical switch (200) is controlled to be closed, and the first power electronic switch (701) of the power electronic switch assembly (4) is triggered to be turned on, so that the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector (1), the second mechanical switch (200), the current limiting resistor (600) of the power electronic switch (2), the first insulating sleeve (801) of the insulating sleeve, the first power electronic switch (701) and the neutral point of the on-load tap changer, and the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector (1), the second mechanical switch (200), the current limiting resistor (600) of the power electronic switch (2), the first insulating sleeve (801) of the insulating sleeve, the first power electronic switch (701) and the neutral point of the on-load tap changer. The invention relates to a power supply device winding, one end of the tap selector (1), a third mechanical switch (300), a fifth mechanical switch (500), a third insulating bushing (803), and a neutral point of the on-load tap changer, and simultaneously causes the current to form a circulating current through one end of the tap selector (1), the third mechanical switch (300), the fifth mechanical switch (500), the third insulating bushing (803), the first power electronic switch (701), the first insulating bushing (801), the current limiting resistor (600), the second mechanical switch (200), and the other end of the tap selector (1);

[0031] The fifth mechanical switch (500) is controlled to be disconnected, and the second power electronic switch (702) of the power electronic switch assembly (4) is triggered to be turned on, so that the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector (1), the second mechanical switch (200), the current limiting resistor (600), the first insulating sleeve (801), the first power electronic switch (701) and the neutral point of the on-load tap changer, and the current flows sequentially through the high-voltage transmission transformer winding, one end of the tap selector (1), the third mechanical switch (702) and the neutral point of the on-load tap changer. The switch (300), the second insulating sleeve (802) of the insulating sleeve, the second power electronic switch (702) and the neutral point of the on-load tap changer, and at the same time, the current is caused to form a circulating current through one end of the tap selector (1), the third mechanical switch (300), the second insulating sleeve (802), the second power electronic switch (702), the first power electronic switch (701), the first insulating sleeve (801), the current limiting resistor (600), the second mechanical switch (200) and the other end of the tap selector (1);

[0032] Triggering the second power electronic switch (702) to turn off, so that current flows through the high-voltage transmission transformer winding, the other end of the tap selector (1), the second mechanical switch (200), the current limiting resistor (600), the first insulating sleeve (801), the first power electronic switch (701) and the neutral point of the on-load tap changer;

[0033] Controlling the third mechanical switch (300) to open, controlling the fourth mechanical switch (400) to close, triggering the second power electronic switch (702) to turn on, and then turning off the first power electronic switch (701), so that the current flows through the high-voltage transmission transformer winding, the other end of the tap selector (1), the fourth mechanical switch (400), the second insulating sleeve (802), the second power electronic switch (702) and the neutral point of the on-load tap changer;

[0034] The fifth mechanical switch (500) is controlled to be closed, and the second power electronic switch (702) is triggered to be turned off, so that the current flows through the high-voltage transmission transformer winding, the other end of the tap selector (1), the fourth mechanical switch (400), the fifth mechanical switch (500), the third insulating bushing (803) and the neutral point of the on-load tap changer.

[0035] The technical solution provided by the present invention has the following beneficial effects:

[0036] The on-load tap changer for a high-voltage transmission transformer provided by the present invention comprises a tap selector (1) and a power electronic switch (2); the power electronic switch (2) comprises a mechanical switch assembly (3), a power electronic switch assembly (4) and an insulating sleeve; the mechanical switch assembly (3) is connected to a high-voltage transmission transformer winding tap via the tap selector (1); the mechanical switch assembly (3) is connected to the power electronic switch assembly (4) via the insulating sleeve; the mechanical switch assembly (3) and the power electronic switch assembly (4) are both connected to the neutral point of the on-load tap changer; the tap selector (1) and the mechanical switch assembly (3) are both located inside the high-voltage transmission transformer; the power electronic switch assembly (4) is located outside the high-voltage transmission transformer; the mechanical switch assembly can achieve arc-free closing and closing, thereby avoiding the occurrence of transformer fire or even explosion, and having high safety;

[0037] In the present invention, the power electronic components in the first power electronic switch and the second power electronic switch are connected at the same potential at both ends. They are only put into operation when the on-load tap changer is in operation, and are bypassed when not in operation. The power electronic switch components do not need to withstand long-term voltage stress during steady-state operation, thus avoiding the first power electronic switch and the second power electronic switch being connected in parallel between transformer turns for a long time. The power electronic switch components can withstand lightning strikes and are not prone to breakdown failure.

[0038] In the present invention, the number of power electronic devices connected in series in the first power electronic switch and the second power electronic switch can be different, and thus the structures of the two can be configured asymmetrically, which greatly reduces the difficulty of series voltage balancing design and the complexity of control;

[0039] The power electronic switch assembly of the present invention uses diodes and / or fully controlled power devices, which can autonomously shut off the current during the switching process, shortening the delay caused by the thyristor relying on the current zero crossing to shut off, improving the switching speed, and reducing the heat generation of the current limiting resistor;

[0040] The on-load tap changer provided by the present invention is a mechanical power electronic hybrid on-load tap changer, which has no arc during the switching process and a long service life;

[0041] The power electronic switch of the present invention requires fewer power electronic switch components, greatly reducing the cost of the on-load tap changer, and has high reliability, while avoiding the voltage balancing problem of power electronic devices connected in series.

[0042] The present invention can realize substantially arc-free opening and closing of each mechanical switch in a mechanical switch assembly, and the opening and closing of the mechanical switch does not need to withstand the voltage drop generated by a large number of power electronic devices and current-limiting resistors connected in series. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 1 is a structural diagram of an on-load tap changer for a high-voltage transmission transformer according to an embodiment of the present invention;

[0044] Figure 2 This is a structural diagram of a first power electronic switch and a second power electronic switch in an embodiment of the present invention;

[0045] Figure 3 is another structural diagram of the first power electronic switch and the second power electronic switch in an embodiment of the present invention;

[0046] Figure 4 is another structural diagram of the first power electronic switch and the second power electronic switch in an embodiment of the present invention;

[0047] Figure 5 Schematic diagram of current flow before on-load tap changer switching in an embodiment of the present invention;

[0048] Figure 6 Schematic diagram of current flow when the first mechanical switch is open, the second mechanical switch is closed, and the first power electronic switch is turned on in an embodiment of the present invention;

[0049] Figure 7 Schematic diagram of current flow when the fifth mechanical switch is disconnected and the second power electronic switch is triggered to turn on in an embodiment of the present invention;

[0050] Figure 8 Schematic diagram of current flow when the second power electronic switch is triggered to turn off the current in an embodiment of the present invention;

[0051] Figure 9 This is a schematic diagram of the current flow when the third mechanical switch is opened, the fourth mechanical switch is closed, and the second power electronic switch is triggered to turn on, and then the first power electronic switch is turned off in accordance with an embodiment of the present invention;

[0052] Figure 10 Schematic diagram of the current flow when the fifth mechanical switch is closed and simultaneously triggers the second power electronic switch to shut off in an embodiment of the present invention;

[0053] Figure 11 This is a flow chart of a method for controlling an on-load tap changer of a high-voltage transmission transformer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0054] The present invention will be described in further detail below with reference to the accompanying drawings.

[0055] Example 1

[0056] Embodiment 1 of the present invention provides an on-load tap changer for a high-voltage transmission transformer, such as Figure 1 As shown, it includes a tap selector 1 and a power electronic switch 2; the power electronic switch 2 includes a mechanical switch component 3, a power electronic switch component 4 and an insulating sleeve;

[0057] The mechanical switch assembly 3 is connected to the high-voltage transmission transformer winding tap through the tap selector 1. The mechanical switch assembly 3 is connected to the power electronic switch assembly 4 through an insulating bushing. Both the mechanical switch assembly 3 and the power electronic switch assembly 4 are connected to the neutral point of the on-load tap changer. The tap selector 1 and the mechanical switch assembly 3 are both located inside the high-voltage transmission transformer, and the power electronic switch assembly 4 is located outside the high-voltage transmission transformer.

[0058] The mechanical switch assembly 3 includes a first mechanical switch 100 , a second mechanical switch 200 , a third mechanical switch 300 , a fourth mechanical switch 400 and a fifth mechanical switch 500 ;

[0059] The first mechanical switch 100 and the third mechanical switch 300 are both connected to one end of the tap selector 1, the second mechanical switch 200 and the fourth mechanical switch 400 are both connected to the other end of the tap selector 1, and the fifth mechanical switch 500 has one end connected to the third mechanical switch 300 and the fourth mechanical switch 400, and the other end connected to the neutral point of the on-load tap changer.

[0060] The tap selector 1 includes a plurality of taps. In the first embodiment of the present invention, the tap selector 1 is provided with three taps.

[0061] The first mechanical switch 100 and the third mechanical switch 300 are connected to the odd-numbered taps of the tap selector 1 , and the second mechanical switch 200 and the fourth mechanical switch 400 are connected to the even-numbered taps of the tap selector 1 .

[0062] The power electronic switch assembly 4 includes a first power electronic switch 701 and a second power electronic switch 702;

[0063] One end of the first power electronic switch 701 is connected to the first mechanical switch 100 and the second mechanical switch 200, and the other end is connected to the neutral point of the on-load tap changer;

[0064] One end of the second power electronic switch 702 is connected to the third mechanical switch 300 and the fourth mechanical switch 400 , and the other end is connected to the neutral point of the on-load tap changer.

[0065] The power electronic switch 2 further includes a current limiting resistor 600, which is located inside the high-voltage transmission transformer;

[0066] One end of the current-limiting resistor 600 is connected to the first mechanical switch 100 and the second mechanical switch 200, and the other end is connected to the first power electronic switch 701. The current-limiting resistor 600 is used to suppress circulating current between the connected and preselected positions during on-load tap changer switching, effectively protecting the power electronic components within the tap changer. The transformer also includes a lightning arrester directly connected to the tap selector and in parallel with both ends of the tap changer to protect the power electronic components within the tap changer from transient overvoltages, providing a secondary layer of protection for the power electronic components.

[0067] The insulating sleeve includes a first insulating sleeve 801, a second insulating sleeve 802 and a third insulating sleeve 803;

[0068] The first insulating sleeve 801 is located between the current limiting resistor 600 and the first power electronic switch 701;

[0069] The second insulating sleeve 802 is located between the third mechanical switch 300 and the fourth mechanical switch 400 and the second power electronic switch 702 ;

[0070] The third insulating sleeve 803 is connected to the neutral point of the third mechanical switch 300 and the fourth mechanical switch 400 and the on-load tap changer.

[0071] The insulating sleeve 801 is a switching branch, used to connect a group of fully controlled devices and transition resistors;

[0072] The insulating sleeve 802 is another switching branch, one end of which is connected to the external fully controlled device, and the other end is directly connected to the mechanical switches 300 and 400 inside the transformer tank;

[0073] The insulating bushing 803 is the main current branch in the non-switching state, one end of which is connected to the mechanical switch 500 inside the transformer tank, and the other end is directly connected to the neutral point of the on-load tap changer.

[0074] The power electronic switch 2 in the embodiment 1 of the present invention further includes an inter-pole lightning arrester, which is arranged inside the transformer and connected to the tap selector 1 .

[0075] like Figure 2 As shown, the first power electronic switch 701 and the second power electronic switch 702 both include a first bridge circuit and a fully controlled power device;

[0076] The first bridge circuit includes four diodes; two of the diodes are connected in series in the same direction (one group of diodes) to form the first half bridge, and the remaining two diodes are connected in series in the same direction (another group of diodes) to form the second half bridge. The first half bridge and the second half bridge are connected in parallel, and the fully controlled power device is connected in parallel between the first half bridge and the second half bridge. The connection terminal of each group of series diodes is connected as the same as the other Figure 2The structure is a series node, two sets of series diodes are connected in parallel in the same direction, and an insulated gate bipolar transistor (IGBT) is connected in parallel to the diodes in the same direction, with its collector connected to the diode cathode and the emitter connected to the diode anode. Figure 2 The structure shown can disconnect bidirectional alternating current while ensuring that both ends of the fully controlled power device IGBT always maintain a forward voltage drop, thereby protecting the IGBT.

[0077] like Figure 3 As shown, the first power electronic switch 701 and the second power electronic switch 702 both include a second bridge circuit and a DC capacitor;

[0078] The second bridge circuit includes four IGBT modules; two of them are connected in series in the same direction (one group of IGBT modules) to form the third half bridge, and the remaining two IGBT modules are connected in series in the same direction (another group of IGBT modules) to form the fourth half bridge. The third half bridge and the fourth half bridge are connected in parallel, and the DC capacitor is connected in parallel between the third half bridge and the fourth half bridge. Every two IGBT modules form a group of same direction series, and the connection point serves as the lead-out node to the next Figure 3 The structure shown is connected in series, with two sets of series-connected IGBT modules connected in parallel in the same direction and then connected in parallel with capacitors to form three parallel connections. This topology can also achieve bidirectional AC disconnection.

[0079] like Figure 4 As shown, the first power electronic switch 701 and the second power electronic switch 702 each include multiple IGBT components connected in series; each IGBT component includes two IGBT modules connected in series in opposite directions. The two IGBT modules are connected in series head to tail to conduct and disconnect bidirectional AC current.

[0080] The first power electronic switch 701 and the second power electronic switch 702 may be composed of one or more Figure 2 、 Figure 3 and Figure 4 The structures shown are connected in series.

[0081] Fully controlled power devices include IGBTs or IGCTs.

[0082] The IGBT module includes an IGBT and a diode connected in anti-parallel with the IGBT.

[0083] The IGBT in the first embodiment of the present invention is driven by a digital IGBT driver, which is powered by a high-potential isolated power supply system.

[0084] Example 2

[0085] Embodiment 2 of the present invention provides a control method for an on-load tap changer of a high-voltage transmission transformer. The specific flow chart is as follows: Figure 11 As shown, the specific process is as follows:

[0086] S101: Before the on-load tap changer is switched, the mechanical switch assembly 3 of the power electronic switch 2 is controlled to make the current flow through the high-voltage transmission transformer winding, one end of the tap selector 1, the mechanical switch assembly 3, the insulating bushing, and the neutral point of the on-load tap changer in sequence;

[0087] S102: During the on-load tap changer switching, the state of the mechanical switch assembly 3 is adjusted, and the power electronic switch assembly 4 of the power electronic switch 2 is triggered at the same time, so that the current flows through the high-voltage transmission transformer winding, the other end of the tap selector 1, the mechanical switch assembly 3, the insulating bushing, and the neutral point of the on-load tap changer in sequence.

[0088] Before the on-load tap changer is switched, the mechanical switch assembly 3 of the power electronic switch 2 is controlled to make the current flow through the high-voltage transmission transformer winding, one end of the tap selector 1, the mechanical switch assembly 3 and the neutral point of the on-load tap changer in sequence, including:

[0089] The first mechanical switch 100, the third mechanical switch 300, and the fifth mechanical switch 500 of the mechanical switch assembly 3 are controlled to be closed, and the second mechanical switch 200 and the fourth mechanical switch 400 of the mechanical switch assembly 3 are controlled to be opened, so that the current flows sequentially through the high-voltage transmission transformer winding, one end of the tap selector 1, the third mechanical switch 300, the fifth mechanical switch 500, the third insulating bushing 803, and the neutral point of the on-load tap changer. The specific current flow direction is as follows: Figure 5 Indicated by the bold line in .

[0090] In the non-switching working state, that is, before the on-load tap changer is switched, the first mechanical switch 100 and the third mechanical switch 300 must be in the same position or the second mechanical switch 200 and the fourth mechanical switch 400 must be in the same position, and the fifth mechanical switch 500 is in the closed state, that is, Figure 5 The first power electronic switch 701 and the second power electronic switch 702 are short-circuited at one point through the current limiting resistor 600, effectively protecting the first power electronic switch 701 and the second power electronic switch 702 from damage caused by overvoltage or other conditions.

[0091] During on-load tap changer switching, the state of the mechanical switch assembly 3 is adjusted, and the power electronic switch assembly 4 of the power electronic switch 2 is triggered simultaneously, so that the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector 1, the mechanical switch assembly 3, and the neutral point of the on-load tap changer, including:

[0092] The first mechanical switch 100 is controlled to be open, the second mechanical switch 200 is controlled to be closed, and the first power electronic switch 701 of the power electronic switch assembly 4 is triggered to be turned on, so that the current flows in sequence through the high-voltage transmission transformer winding, the other end of the tap selector 1, the second mechanical switch 200, the current-limiting resistor 600 of the power electronic transfer switch 2, the first insulating bushing 801, the first power electronic switch 701, and the neutral point of the on-load tap changer. The current also flows in sequence through the high-voltage transmission transformer winding, one end of the tap selector 1, the third mechanical switch 300, the fifth mechanical switch 500, the third insulating bushing 803, and the neutral point of the on-load tap changer. At the same time, the current forms a loop through one end of the tap selector 1, the third mechanical switch 300, the fifth mechanical switch 500, the third insulating bushing 803, the first power electronic switch 701, the first insulating bushing 801, the current-limiting resistor 600, the second mechanical switch 200, and the other end of the tap selector 1. The current flow direction is as follows: Figure 6 As shown by the bold line in

[0093] The fifth mechanical switch 500 is controlled to be disconnected, and the second power electronic switch 702 of the power electronic switch assembly 4 is triggered to be turned on, so that the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector 1, the second mechanical switch 200, the current-limiting resistor 600, the first insulating bushing 801, the first power electronic switch 701, and the neutral point of the on-load tap changer. The current also flows sequentially through the high-voltage transmission transformer winding, one end of the tap selector 1, the third mechanical switch 300, the second insulating bushing 802, the second power electronic switch 702, and the neutral point of the on-load tap changer. At the same time, the current forms a circulating current through one end of the tap selector 1, the third mechanical switch 300, the second insulating bushing 802, the second power electronic switch 702, the first power electronic switch 701, the first insulating bushing 801, the current-limiting resistor 600, the second mechanical switch 200, and the other end of the tap selector 1. The specific current flow direction is as follows: Figure 7 As shown by the bold line in

[0094] The second power electronic switch 702 is triggered to turn off, so that the current flows through the high-voltage transmission transformer winding, the other end of the tap selector 1, the second mechanical switch 200, the current limiting resistor 600, the first insulating sleeve 801, the first power electronic switch 701 and the neutral point of the on-load tap changer. The specific current flow direction is as follows: Figure 8 As shown by the bold line in

[0095] The third mechanical switch 300 is controlled to be opened, the fourth mechanical switch 400 is controlled to be closed, the second power electronic switch 702 is triggered to be turned on, and then the first power electronic switch 701 is turned off, so that the current flows through the high-voltage transmission transformer winding, the other end of the tap selector 1, the fourth mechanical switch 400, the second insulating sleeve 802, the second power electronic switch 702 and the neutral point of the on-load tap changer. The specific current flow direction is as follows: Figure 9 As shown by the bold line in

[0096] The fifth mechanical switch 500 is controlled to be closed, and the second power electronic switch 702 is triggered to be turned off, so that the current flows through the high-voltage transmission transformer winding, the other end of the tap selector 1, the fourth mechanical switch 400, the fifth mechanical switch 500, the third insulating sleeve 803 and the neutral point of the on-load tap changer. The specific current flow direction is as follows: Figure 10 As shown by the bold line in , at this time, the on-load tap changer is switched from one gear to another.

[0097] For the convenience of description, the various parts of the above device are divided into various modules or units according to their functions and described separately. Of course, when implementing this application, the functions of each module or unit can be implemented in the same or multiple software or hardware.

[0098] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0099] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0100] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0101] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0102] 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. Ordinary technicians in the relevant field can still modify or replace the specific implementation methods of the present invention with equivalents by referring to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the present invention to be approved.

Claims

1. An on-load tap changer for a high-voltage transmission transformer, characterized in that: It comprises a tap selector (1) and a power electronic switch (2); the power electronic switch (2) comprises a mechanical switch component (3), a power electronic switch component (4) and an insulating sleeve; The mechanical switch assembly (3) is connected to a high-voltage transmission transformer winding tap via a tap selector (1), the mechanical switch assembly (3) is connected to a power electronic switch assembly (4) via an insulating bushing, and both the mechanical switch assembly (3) and the power electronic switch assembly (4) are connected to a neutral point of an on-load tap changer, and the tap selector (1) and the mechanical switch assembly (3) are both located inside the high-voltage transmission transformer, and the power electronic switch assembly (4) is located outside the high-voltage transmission transformer; The mechanical switch assembly (3) comprises a first mechanical switch (100), a second mechanical switch (200), a third mechanical switch (300), a fourth mechanical switch (400) and a fifth mechanical switch (500); The first mechanical switch (100) and the third mechanical switch (300) are both connected to one end of the tap selector (1), the second mechanical switch (200) and the fourth mechanical switch (400) are both connected to the other end of the tap selector (1), and the fifth mechanical switch (500) has one end connected to the third mechanical switch (300) and the fourth mechanical switch (400), and the other end connected to the neutral point of the on-load tap changer; The power electronic switch assembly (4) comprises a first power electronic switch (701) and a second power electronic switch (702); One end of the first power electronic switch (701) is connected to the first mechanical switch (100) and the second mechanical switch (200), and the other end is connected to the neutral point of the on-load tap changer; One end of the second power electronic switch (702) is connected to the third mechanical switch (300) and the fourth mechanical switch (400), and the other end is connected to the neutral point of the on-load tap changer; The power electronic switching switch (2) further comprises a current limiting resistor (600), and the current limiting resistor (600) is located inside the high-voltage transmission transformer.

2. The on-load tap changer for a high-voltage transmission transformer according to claim 1, characterized in that: One end of the current limiting resistor (600) is connected to the first mechanical switch (100) and the second mechanical switch (200), and the other end is connected to the first power electronic switch (701).

3. The on-load tap changer for a high-voltage transmission transformer according to claim 2, characterized in that: The insulating sleeve comprises a first insulating sleeve (801), a second insulating sleeve (802) and a third insulating sleeve (803); The first insulating sleeve (801) is located between the current limiting resistor (600) and the first power electronic switch (701); The second insulating sleeve (802) is located between the third mechanical switch (300), the fourth mechanical switch (400) and the second power electronic switch (702); The third insulating sleeve (803) is located at the neutral point of the third mechanical switch (300) and the fourth mechanical switch (400) and is connected to the on-load tap changer.

4. The on-load tap changer for a high-voltage transmission transformer according to claim 1, characterized in that: The first power electronic switch (701) and the second power electronic switch (702) both include a first bridge circuit and a fully controlled power device; The first bridge circuit includes four diodes; Two diodes are connected in series in the same direction to form a first half-bridge, and the remaining two diodes are connected in series in the same direction to form a second half-bridge. The first half-bridge and the second half-bridge are connected in parallel, and the fully-controlled power device is connected in parallel between the first half-bridge and the second half-bridge.

5. The on-load tap changer for a high-voltage transmission transformer according to claim 1, characterized in that: The first power electronic switch (701) and the second power electronic switch (702) both include a second bridge circuit and a DC capacitor; The second bridge circuit includes four IGBT modules; two of the IGBT modules are connected in series in the same direction to form a third half-bridge, and the remaining two IGBT modules are connected in series in the same direction to form a fourth half-bridge. The third half-bridge and the fourth half-bridge are connected in parallel, and the DC capacitor is connected in parallel between the third half-bridge and the fourth half-bridge.

6. The on-load tap changer for a high-voltage transmission transformer according to claim 1, characterized in that: The first power electronic switch (701) and the second power electronic switch (702) each comprise a plurality of IGBT components connected in series; Each IGBT assembly consists of two IGBT modules connected in series.

7. The on-load tap changer for a high-voltage transmission transformer according to claim 4, characterized in that: The fully controlled power device includes an IGBT or an IGCT.

8. The on-load tap changer for a high-voltage transmission transformer according to claim 5 or 6, characterized in that: The IGBT module includes an IGBT and a diode connected in anti-parallel with the IGBT.

9. A control method for an on-load tap changer of a high-voltage transmission transformer, characterized in that: include: Before the on-load tap changer is switched, the mechanical switch assembly (3) of the power electronic switch (2) is controlled to make the current flow through the high-voltage transmission transformer winding, one end of the tap selector (1), the mechanical switch assembly (3), the insulating bushing and the neutral point of the on-load tap changer in sequence; During the on-load tap changer switching, the state of the mechanical switch assembly (3) is adjusted, and the power electronic switch assembly (4) of the power electronic switch (2) is triggered simultaneously, so that the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector (1), the mechanical switch assembly (3), the insulating bushing and the neutral point of the on-load tap changer; Controlling the first mechanical switch (100), the third mechanical switch (300), and the fifth mechanical switch (500) of the mechanical switch assembly (3) to close, and controlling the second mechanical switch (200) and the fourth mechanical switch (400) of the mechanical switch assembly (3) to open, so that current flows sequentially through the high-voltage transmission transformer winding, one end of the tap selector (1), the third mechanical switch (300), the fifth mechanical switch (500), the third insulating bushing (803) of the insulating bushing, and the neutral point of the on-load tap changer; The power electronic switch assembly (4) comprises a first power electronic switch (701) and a second power electronic switch (702); One end of the first power electronic switch (701) is connected to the first mechanical switch (100) and the second mechanical switch (200), and the other end is connected to the neutral point of the on-load tap changer; One end of the second power electronic switch (702) is connected to the third mechanical switch (300) and the fourth mechanical switch (400), and the other end is connected to the neutral point of the on-load tap changer; The power electronic switching switch (2) further comprises a current limiting resistor (600), and the current limiting resistor (600) is located inside the high-voltage transmission transformer.

10. The control method for an on-load tap changer of a high-voltage transmission transformer according to claim 9, characterized in that: The method comprises adjusting the state of the mechanical switch assembly (3) and triggering the power electronic switch assembly (4) of the power electronic switch (2) during the switching of the on-load tap changer, so that the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector (1), the mechanical switch assembly (3) and the neutral point of the on-load tap changer, including: The first mechanical switch (100) is controlled to be disconnected, the second mechanical switch (200) is controlled to be closed, and the first power electronic switch (701) of the power electronic switch assembly (4) is triggered to be turned on, so that the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector (1), the second mechanical switch (200), the current limiting resistor (600) of the power electronic switch (2), the first insulating sleeve (801) of the insulating sleeve, the first power electronic switch (701) and the neutral point of the on-load tap changer, and the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector (1), the second mechanical switch (200), the current limiting resistor (600) of the power electronic switch (2), the first insulating sleeve (801) of the insulating sleeve, the first power electronic switch (701) and the neutral point of the on-load tap changer. The invention relates to a power supply device winding, one end of the tap selector (1), the third mechanical switch (300), the fifth mechanical switch (500), the third insulating bushing (803) and the neutral point of the on-load tap changer, and simultaneously causes the current to form a circulating current through one end of the tap selector (1), the third mechanical switch (300), the fifth mechanical switch (500), the third insulating bushing (803), the first power electronic switch (701), the first insulating bushing (801), the current limiting resistor (600), the second mechanical switch (200) and the other end of the tap selector (1); The fifth mechanical switch (500) is controlled to be disconnected, and the second power electronic switch (702) of the power electronic switch assembly (4) is triggered to be turned on, so that the current flows sequentially through the high-voltage transmission transformer winding, the other end of the tap selector (1), the second mechanical switch (200), the current limiting resistor (600), the first insulating sleeve (801), the first power electronic switch (701) and the neutral point of the on-load tap changer, and the current flows sequentially through the high-voltage transmission transformer winding, one end of the tap selector (1), the third mechanical switch (702) and the neutral point of the on-load tap changer. The switch (300), the second insulating sleeve (802) of the insulating sleeve, the second power electronic switch (702) and the neutral point of the on-load tap changer, and at the same time, the current is caused to form a circulating current through one end of the tap selector (1), the third mechanical switch (300), the second insulating sleeve (802), the second power electronic switch (702), the first power electronic switch (701), the first insulating sleeve (801), the current limiting resistor (600), the second mechanical switch (200) and the other end of the tap selector (1); Triggering the second power electronic switch (702) to turn off, so that current flows through the high-voltage transmission transformer winding, the other end of the tap selector (1), the second mechanical switch (200), the current limiting resistor (600), the first insulating sleeve (801), the first power electronic switch (701) and the neutral point of the on-load tap changer; Controlling the third mechanical switch (300) to open, controlling the fourth mechanical switch (400) to close, triggering the second power electronic switch (702) to turn on, and then turning off the first power electronic switch (701), so that the current flows through the high-voltage transmission transformer winding, the other end of the tap selector (1), the fourth mechanical switch (400), the second insulating sleeve (802), the second power electronic switch (702) and the neutral point of the on-load tap changer; The fifth mechanical switch (500) is controlled to be closed, and the second power electronic switch (702) is triggered to be turned off, so that the current flows through the high-voltage transmission transformer winding, the other end of the tap selector (1), the fourth mechanical switch (400), the fifth mechanical switch (500), the third insulating bushing (803) and the neutral point of the on-load tap changer.

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