A hybrid arc-free switching structure for a bridge-arm type on-load tap changer

Abstract

This utility model relates to a hybrid arc-free switching switch structure for a bridge-arm type on-load tap changer, comprising: multiple composite bridge-arm switch units and multiple composite transition switch units; the composite bridge-arm switch units are connected between the taps of the multi-tap voltage regulating winding and the upper or lower output bus, each unit including a bridge-arm mechanical switch and a parallel first solid-state bypass branch, used to conduct before the mechanical switch actuates to achieve arc-free switching; the composite transition switch units are connected between the bridge-arm input common node and the upper or lower output bus, each unit including a transition mechanical switch and a parallel second solid-state bypass branch, used to provide a temporary current path and achieve arc-free switching during the switching process. This device can achieve zero-current contact opening and closing to eliminate arcing, and features both long life and low loss.

Description

Technical Field

[0001] This utility model belongs to the field of on-load tap changer technology for power equipment, specifically relating to a hybrid arc-free switching switch structure for a bridge-arm type on-load tap changer. Background Technology

[0002] During power system operation, the bridge-arm type on-load tap changing device combines different potentials of the multi-tap tap changing winding through the upper and lower bridge-arm switch groups to achieve multi-stage voltage regulation of the transformer under load. The bridge-arm switches in this device are used to selectively connect to different tap potentials, and a transition mechanical switch is provided to provide a temporary closed current path during the switching of adjacent taps, ensuring continuous current on the load side.

[0003] However, in the actual operation of bridge-arm type on-load tap changers, whether it's the switching of the bridge arm switch or the conduction and disconnection of the transition mechanical switch, its mechanical contacts must withstand the switching of load current at the moment of opening or closing. At the moment of contact separation, due to the presence of inductive load and line inductance in the circuit, an electric arc is inevitably generated in the contact gap. The high temperature of the arc causes the contact surface material to evaporate, oxidize, and ablate, resulting in increased contact resistance and irregular contact surface after long-term operation, ultimately affecting the switch's conduction performance and service life.

[0004] In existing technologies, to alleviate the arcing problem, methods such as switching within the insulating oil (oil-immersed on-load tap changers), setting up arc-extinguishing chambers, or adding arc-extinguishing grids are commonly used. While oil-immersed solutions can effectively extinguish arcs, they suffer from problems such as high maintenance workload, the need for regular oil replacement due to deterioration, and poor environmental performance. Arc-extinguishing chamber solutions increase the size and structural complexity of the device, and their arc-extinguishing effect is significantly affected by the magnitude of the breaking current and the contact gap distance. None of the above solutions fundamentally eliminate the arcing problem caused by the opening and closing of mechanical contacts under current-carrying conditions. Utility Model Content

[0005] To address the aforementioned problems in the existing technology, this utility model provides a hybrid arc-free switching switch structure for a bridge-arm type on-load tap changer. The technical problem to be solved by this utility model is achieved through the following technical solution: This utility model provides a hybrid arc-free switching structure for a bridge-arm type on-load tap changer. The bridge-arm type on-load tap changer includes a multi-tap tap changing winding, a bridge arm input common node, an upper output bus, and a lower output bus. The hybrid arc-free switching structure includes multiple composite bridge arm switching units and multiple composite transition switching units. Some of the composite bridge arm switch units are electrically connected between the taps of the multi-tap voltage regulating winding and the upper output bus, while the remaining composite bridge arm switch units are electrically connected between the taps of the multi-tap voltage regulating winding and the lower output bus. Each composite bridge arm switch unit includes a bridge arm mechanical switch and a first solid-state bypass branch connected in parallel with it. The bridge arm mechanical switch is used to turn on or off during voltage regulation to connect different tap potentials to the upper output bus or the lower output bus. The first solid-state bypass branch is used to turn on before the bridge arm mechanical switch is activated to achieve arc-free switching. Some of the composite transition switch units are electrically connected between the bridge arm input common node and the upper output bus, while the remaining composite bridge arm switch units are electrically connected between the bridge arm input common node and the lower output bus. Each composite transition switch unit includes a transition mechanical switch and a second solid-state bypass branch connected in parallel with it. The transition mechanical switch is used to turn on or off during the voltage regulation gear switching process to provide a temporary closed current path. The second solid-state bypass branch is used to turn on before the transition mechanical switch is activated to achieve arc-free switching.

[0006] Compared with the prior art, the beneficial effects of this utility model are as follows: To address the issue that existing solutions fail to fundamentally eliminate the arcing problem caused by the opening and closing of mechanical contacts under current-carrying conditions, this invention provides a hybrid arc-free switching switch structure for a bridge-arm type on-load tap changer. This structure comprises a composite bridge-arm switch unit and a composite transition switch unit, formed by connecting a solid-state bypass branch consisting of anti-parallel power semiconductor switches in parallel across each bridge-arm mechanical switch and each transition mechanical switch. The solid-state bypass branch conducts before the corresponding mechanical switch operates, transferring the load current to the solid-state bypass branch at the instant the mechanical contacts open or close. This ensures that all mechanical contacts open or close under zero-current conditions, fundamentally eliminating switching arcs, preventing contact erosion, and significantly extending the service life of the mechanical switches. Furthermore, the solid-state bypass branch conducts only briefly during the switching transition; during steady-state operation of the tap changer, the load current is entirely borne by the mechanical contacts, without introducing additional conduction losses or heat dissipation burdens. This structure combines the advantages of low loss in mechanical switches and arc-free switching in solid-state switches. Moreover, this structure does not require changes to the original topology of the bridge-arm type on-load tap changer, offering good compatibility and low engineering implementation difficulty. Attached Figure Description

[0007] Figure 1 This is an internal structural diagram of a hybrid arc-free switching switch structure for a bridge-arm type on-load tap changer provided in this utility model embodiment; Figure 2This is a schematic diagram of the specific structure of a composite transition switch unit or a composite transition switch unit provided in an embodiment of this utility model; Figure 3 This utility model provides an old gear bridge arm switch T. x Timing diagram of electromechanical coordinated zero-current disconnection during disconnection.

[0008] Explanation of icon numbers: 1-Multi-tap voltage regulating winding; 2-Bridge arm input common node; 3a-Upper output bus; 3b-Lower output bus; 4-Control circuit; 5-Load. Detailed Implementation

[0009] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0010] The hybrid arc-free switching switch structure of the bridge arm type on-load tap changer proposed in this utility model will now be described in detail with reference to the accompanying drawings.

[0011] Figure 1 This is an internal structural diagram of a hybrid arc-free switching switch structure for a bridge-arm type on-load tap changer provided in this embodiment of the utility model. Figure 1 As shown, the bridge arm type on-load tap changing device includes a multi-tap tap changing winding 1, a bridge arm input common node 2, an upper output bus 3a, and a lower output bus 3b; the hybrid arc-free switching structure includes: multiple composite bridge arm switching units and multiple composite transition switching units. Some of the composite bridge arm switching units are electrically connected to the taps of the multi-tap tap changing winding 1 ( Figure 1 The example shows the three taps of tap ac) between the upper output bus 3a and the remaining composite bridge arm switch unit is electrically connected between the taps of the multi-tap voltage regulating winding 1 and the lower output bus 3b. Each composite bridge arm switch unit includes a bridge arm mechanical switch and a first solid-state bypass branch connected in parallel with it. The bridge arm mechanical switch is used to turn on or off during voltage regulation to connect different tap potentials to the upper output bus 3a or the lower output bus 3b. The first solid-state bypass branch is used to turn on before the bridge arm mechanical switch is activated to achieve arc-free switching. Some of the composite transition switch units are electrically connected between the bridge arm input common node 2 and the upper output bus 3a, while the remaining composite bridge arm switch units are electrically connected between the bridge arm input common node 2 and the lower output bus 3b. Each composite transition switch unit includes a transition mechanical switch and a second solid-state bypass branch connected in parallel with it. The transition mechanical switch is used to turn on or off during the voltage regulation gear switching process to provide a temporary closed current path. The second solid-state bypass branch is used to turn on before the transition mechanical switch operates to achieve arc-free switching.

[0012] It should be noted that the multi-tap regulating winding 1, bridge arm input common node 2, upper output bus 3a, and lower output bus 3b included in the bridge arm type on-load tap changer are all well-known components in the art and are not improvements of this utility model. The improvement of this utility model lies in the following hybrid arc-free switching switch structure. Furthermore, the reason for the existence of different tap potentials is that the multi-tap regulating winding 1 has multiple electrical leads (i.e., taps) at different positions along the winding axis on the voltage regulating side of the transformer, each tap corresponding to a different number of coil turns. Since the induced electromotive force is the same for each turn in the transformer winding, taps with different numbers of turns have different voltage potentials, thus providing multiple selectable voltage levels for the bridge arm type on-load tap changer. By selectively connecting different taps, the voltage connected to the load side can be changed, achieving on-load tap regulation.

[0013] It should be noted that the external voltage regulator controller (not shown in the figure) is independent of the hybrid arc-free switching switch structure of this utility model. It is used to monitor the transformer output voltage and issue a range switching command (i.e., voltage regulation range switching) according to the voltage regulation requirements. When it is necessary to change the output voltage, the voltage regulator controller sends the command to the switching command input terminal of the control circuit 4. After receiving the range switching command, the control circuit 4 automatically completes a series of operations according to the preset timing logic (i.e., first triggering the thyristors in each solid-state bypass branch to conduct, and then driving the corresponding mechanical switch to act), such as opening the old range bridge arm switch, turning on the transition mechanical switch, closing the new range bridge arm switch, and deactivating the transition mechanical switch, thereby realizing the arc-free switching of the entire voltage regulation range. The specific internal structure and working process of the control circuit 4 will be discussed in the following text. Figure 3 Detailed description.

[0014] Please continue to refer to Figure 1 Multiple composite bridge arm switch units include a first upper bridge arm switch T1, a second upper bridge arm switch T2, a third upper bridge arm switch T3, a first lower bridge arm switch T4, a second lower bridge arm switch T5, and a third lower bridge arm switch T6; each bridge arm switch corresponds to a first solid-state bypass branch; wherein, one end of the first upper bridge arm switch T1, one end of the second upper bridge arm switch T2, and one end of the third upper bridge arm switch T3 are respectively electrically connected to the corresponding taps of the multi-tap voltage regulating winding 1, and the other end of each is electrically connected to the upper output bus 3a; one end of the first lower bridge arm switch T4, one end of the second lower bridge arm switch T5, and one end of the third lower bridge arm switch T6 are respectively electrically connected to the corresponding taps of the multi-tap voltage regulating winding 1, and the other end of each is electrically connected to the lower output bus 3b.

[0015] It should be understood that the repeated use of "upper" and "lower" before "arm switch" here is to clearly distinguish the position of each arm switch in the arm-type on-load tap changer and its corresponding output bus. It also facilitates the subsequent description of the parallel position and control timing of its corresponding solid-state bypass branch. This naming method is only for clarity and does not constitute an additional limitation on the switch structure or function.

[0016] It should be noted that in the bridge arm type on-load tap changer, the bridge arm switches (such as upper bridge arm switches T1~T3 and lower bridge arm switches T4~T6) are traditional mechanical switches used to select different tap potentials, and are existing components known in the art. By connecting each bridge arm switch in parallel with a first solid-state bypass branch, a composite bridge arm switch unit is formed, and the zero-current, arc-free switching of the mechanical contacts is achieved by controlling the signal transmission timing through control circuit 4.

[0017] Here, multiple composite transition switch units include a first transition mechanical switch K1 and a second transition mechanical switch K2; the first transition mechanical switch K1 is electrically connected between the bridge arm input common node 2 and the upper output bus 3a, and the second transition mechanical switch K2 is electrically connected between the bridge arm input common node 2 and the lower output bus 3b; each transition mechanical switch corresponds to a second solid-state bypass branch.

[0018] Similarly, the transition mechanical switch is a known existing component in the art. By connecting each transition mechanical switch in parallel with a second solid-state bypass branch, a composite transition switch unit is formed, and the timing of signal transmission is controlled by control circuit 4 to achieve zero-current, arc-free switching of the mechanical contacts.

[0019] The specific structural composition of the first solid-state bypass branch and the second solid-state bypass branch will now be described. Figure 2 This is a schematic diagram of the specific structure of a composite bridge arm switch unit provided in an embodiment of this utility model. (See attached diagram.) Figure 2 As shown, Figure 2 In this context, "mechanical switch" refers to the bridge arm mechanical switch; "bus" can refer to the upper output bus 3a or the lower output bus 3b; "tap" refers to one tap in the multi-tap regulating winding 1; and "solid-state bypass branch" refers to the first solid-state bypass branch, which includes two reverse-connected thyristors. It should be understood that... Figure 2 It can also refer to the specific structure of a composite transition switch unit. Among them, Figure 2 The mechanical switch in the circuit is a transitional mechanical switch, and the solid-state bypass branch is the second solid-state bypass branch. The first solid-state bypass branch and the second solid-state bypass branch have the same structure.

[0020] Specifically, each first solid-state bypass branch includes a first thyristor SCR-a and a second thyristor SCR-b; the anode of the first thyristor SCR-a is electrically connected to the cathode of the second thyristor SCR-b, forming the first connection terminal of the first solid-state bypass branch; the cathode of the first thyristor SCR-a is electrically connected to the anode of the second thyristor SCR-b, forming the second connection terminal of the first solid-state bypass branch; the first connection terminal of the first solid-state bypass branch is electrically connected to the terminal of the corresponding bridge arm mechanical switch near the tap of the multi-tap voltage regulating winding 1, and the second connection terminal of the first solid-state bypass branch is electrically connected to the terminal of the corresponding bridge arm mechanical switch near the upper output bus 3a or the lower output bus 3b, thereby making the first solid-state bypass branch and the corresponding bridge arm mechanical switch connected in parallel.

[0021] Furthermore, each second solid-state bypass branch includes a third thyristor and a fourth thyristor; the anode of the third thyristor is electrically connected to the cathode of the fourth thyristor to form the first connection terminal of the second solid-state bypass branch; the cathode of the third thyristor is electrically connected to the anode of the fourth thyristor to form the second connection terminal of the second solid-state bypass branch; the first connection terminal of the second solid-state bypass branch is electrically connected to the terminal of the corresponding transition mechanical switch near the bridge arm input common node 2, and the second connection terminal of the second solid-state bypass branch is electrically connected to the terminal of the corresponding transition mechanical switch near the upper output bus 3a or the lower output bus 3b, thereby enabling the second solid-state bypass branch to be connected in parallel with the transition mechanical switch.

[0022] It should be noted that each thyristor has the same structure, which is a silicon controlled rectifier, with an anode, a cathode and a gate. The silicon controlled rectifier is configured such that: the rated voltage is not less than twice the voltage step between adjacent taps in the multi-tap voltage regulating winding 1, the rated current is not less than 1.5 times the rated load current of the bridge arm type on-load tap changer; and it will turn off naturally when the current flowing through the silicon controlled rectifier drops below the holding current. The reason for these limitations is that: in the solid-state bypass branch, the thyristor is responsible for conducting before the mechanical switch operates and for bearing the full load current. If its rated voltage is less than twice the voltage step size, it may be damaged by transient overvoltages generated during adjacent tap switching. Selecting the rated current with a 1.5-fold margin ensures that the thyristor can still conduct safely without overheating under the most severe load conditions. Furthermore, the "natural turn-off" characteristic (i.e., automatic turn-off when the current crosses zero or drops below the holding current) ensures that the thyristor conducts only for a millisecond-level period during the switching process. After the mechanical switch closes or opens, the current naturally transfers to the mechanical contact path, and the thyristor turns off automatically as the current drops below the holding current, eliminating the need for an additional turn-off circuit and ensuring zero loss during steady-state operation. The above parameter configuration balances device reliability with fully leveraging the thyristor's advantage of natural commutation in AC circuits.

[0023] Please continue to refer to Figure 1A load 5 is connected in series between the upper output bus 3a and the lower output bus 3b, forming the output terminal of the bridge arm type on-load tap changer. This means that the bridge arm type on-load tap changer supplies power to external loads (such as electrical equipment on the secondary side of the transformer) through the upper and lower output buses; the upper output bus 3a and the lower output bus 3b respectively collect the outputs of the upper bridge arm switch group and the lower bridge arm switch group, and the load 5 is connected between the two to form a complete power supply circuit, which together constitute the power output port of the entire tap changer.

[0024] After describing the hardware structure of the composite bridge arm switch unit, composite transition switch unit, and output load, a core component is needed to coordinate the sequence of switch actions in order to achieve truly arc-free switching of the mechanical contacts. Please refer to [link to relevant documentation]. Figure 1 The hybrid arc-free switching switch structure also includes a control circuit 4. This control circuit 4 receives the gear switching command from the external voltage regulator controller and sends control signals to the gates of each thyristor and the drive mechanism of each mechanical switch according to the sequence of "first turning on the thyristors, then operating the mechanical switches," thereby ensuring that each mechanical switch completes opening and closing under zero-current conditions. Specifically, the control circuit 4 includes: The switching command input terminal is connected to the signal control terminal of an external voltage regulator controller to receive gear switching commands from the voltage regulator controller. The drive power input terminal is used to connect to an external drive power supply; The first signal output terminal is electrically connected to the gate of each thyristor; The second signal output terminal is electrically connected to the drive mechanism of each bridge arm switch and the drive mechanism of each transition mechanical switch; The first time delay relay has its coil connected to the switching command input terminal, and its normally open contact connected between the first signal output terminal and the drive power input terminal. The second time-delay relay has its coil connected to the switching command input terminal, and its normally open contact connected between the second signal output terminal and the drive power input terminal; the operating time of the first time-delay relay is shorter than the operating time of the second time-delay relay. When the shift command input terminal receives a shift command, the external drive power supply supplies power to the first signal output terminal via the normally open contact of the first time delay relay to trigger each solid-state bypass branch electrically connected to the first signal output terminal, and supplies power to the second signal output terminal via the normally open contact of the second time delay relay to trigger the drive mechanism of each mechanical switch electrically connected to the second signal output terminal.

[0025] It should be noted that the gear shifting command is equivalent to a trigger signal that simultaneously activates two time-delay relays within control circuit 4. Upon receiving the command, control circuit 4 uses only the first and second time-delay relays to time the operation. The first time-delay relay, with its shorter action time, closes its normally open contact first, allowing external power to supply power to the gates of each thyristor via the first signal output, triggering all solid-state bypass branches to conduct. Subsequently, the second time-delay relay, with its longer action time, closes its normally open contact later, allowing external power to supply power to the drive mechanisms of each mechanical switch via the second signal output, driving the bridge arm switch or transition mechanical switch to perform opening or closing actions. Thus, the inherent time difference between the two time-delay relays achieves the timing sequence of "thyristor conduction first, mechanical switch operation later." The entire process requires no software intervention; the accuracy and reliability of the timing are entirely guaranteed by the hardware delay circuit.

[0026] The working principle of the hybrid arc-free switching switch structure of the bridge arm type on-load tap changer proposed in this utility model will now be explained with specific examples.

[0027] Figure 3 This utility model provides an old gear bridge arm switch T. x The timing diagram shows the electromechanical coordinated zero-current disconnection process during disconnection. It should be noted that the closing and opening of the transition mechanical switch and the closing of the new tap position bridge arm switch both follow a similar timing logic of "conducting the thyristor first, then operating the mechanical switch" to ensure that all mechanical contacts operate under zero-current conditions throughout the entire voltage regulation switching process, completely eliminating the arc. Here, T... x Generally refers to any bridge arm mechanical switch that is currently conducting and needs to be disconnected during voltage regulation switching.

[0028] like Figure 3 As shown, when the on-load tap changer receives the tap changer position switching command, the disconnection process of the old position tap changer switch (taking the first upper tap changer switch T1 as an example) proceeds in the following sequence: Time t0 (steady-state operation): T1 is in the closed state, load current I load All flow passes through the mechanical contact of T1, and the thyristors SCR1a and SCR1b in the first solid-state bypass branch corresponding to T1 are both in the off state.

[0029] At time t1 (first solid-state bypass branch is turned on): Control circuit 4 sends a trigger pulse signal to the gate of the thyristor in the first solid-state bypass branch corresponding to T1. Depending on the current load current direction, SCR1a or SCR1b is turned on. Since the voltage drop across the thyristor after it is turned on (about 1-2V) is lower than the contact resistance voltage drop when the mechanical contacts are closed (especially when the contact resistance increases sharply when the contacts are about to separate), the load current begins to shift from the mechanical contacts to the first solid-state bypass branch.

[0030] Time t1 to t2 (current transfer process): The first solid-state bypass branch is connected in parallel with the mechanical contact, and the two paths are split according to their respective impedances. As the control circuit 4 drives the mechanical contact to start to loosen (the contact pressure decreases and the contact resistance increases), the current flowing through the mechanical contact gradually decreases, and the current flowing through the first solid-state bypass branch gradually increases until the load current is basically transferred to the solid-state bypass branch.

[0031] Time t2 (zero current breaking of mechanical contacts): When the current in the mechanical contacts drops to near zero, the control circuit sends a signal to drive the mechanical contacts of T1 to completely disconnect. Since there is basically no current flowing through the mechanical contacts at this time, no electric arc is generated during the contact separation process.

[0032] Time intervals t2 to t3 (first solid-state bypass branch remains conducting): After the mechanical contacts of T1 are completely disconnected, the entire load current is borne by the first solid-state bypass branch. This stage lasts for an extremely short time (milliseconds), providing only transition time for subsequent mechanical switch operation or the closing of the new gear bridge arm switch.

[0033] Time intervals t3 to t4 (first solid-state bypass branch turned off): After the transition mechanical switch (such as K1 or K2) completes its conduction, the current in the solid-state bypass branch corresponding to T1 gradually decreases. When the current in the thyristor drops below its holding current, the thyristor naturally turns off, the first solid-state bypass branch exits the working state, and the system enters the next voltage regulation stage.

[0034] After the old gear lever switch is opened and before the new gear lever switch is closed, a transition mechanical switch (taking K1 or K2 as an example) needs to be conducted to provide a temporary current path. Its operating sequence is as follows: The control circuit 4 first sends a trigger signal to the gate of the thyristor in the second solid-state bypass branch corresponding to the transition mechanical switch, so that the second solid-state bypass branch is turned on first to establish a current path. Subsequently, the control circuit drives the contacts of the transition mechanical switch to close. Since the second solid-state bypass branch is already carrying current, the mechanical contacts do not experience a sudden current change at the moment of closure, thus avoiding closure arcing and arcing caused by contact bounce. After the mechanical contacts are fully closed, because the contact resistance of the mechanical contacts is much lower than the on-state voltage drop of the thyristor, the load current naturally shifts from the second solid-state bypass branch back to the mechanical contact path, and the thyristor naturally turns off as the current drops below the holding current.

[0035] The closing process of the new gear bridge arm switch is completely consistent with the closing logic of the aforementioned transition mechanical switch: the control circuit 4 first sends a trigger signal to the thyristor in the first solid-state bypass branch corresponding to the new gear bridge arm switch, so that the first solid-state bypass branch is turned on; then, the contacts of the new gear bridge arm mechanical switch close; after the mechanical contacts are fully closed, the load current naturally transfers back to the mechanical contact path, and the thyristor naturally turns off.

[0036] After the new gear bridge arm switch enters steady-state conduction, the transition mechanical switch needs to be disconnected to exit the temporary path: the control circuit 4 first sends a trigger signal to the thyristor in the second solid-state bypass branch corresponding to the transition mechanical switch, so that the second solid-state bypass branch is turned on and takes over the load current; then, the contact of the transition mechanical switch is driven to open (at this time, the current in the mechanical contact is basically zero, realizing zero current interruption); finally, the current in the thyristor naturally drops below the holding current and turns off, and the transition mechanical switch is completely withdrawn.

[0037] In summary, whether it's the opening of the old-position bridge arm switch, the closing of the new-position bridge arm switch, or the engagement and disengagement of the transition mechanical switch, the operation of all mechanical switches strictly follows the sequence of "first triggering the thyristor in the corresponding solid-state bypass branch to conduct, then operating the mechanical contacts to open or close after the load current has transferred to the thyristor branch, and finally the thyristor automatically turns off due to the current naturally crossing zero or dropping below the holding current." During this process, the opening and closing of all mechanical contacts are completed under zero or near-zero current conditions, without generating any electric arc, thus fundamentally solving the problems of contact erosion and short lifespan in traditional on-load tap changers.

[0038] To address the issue that existing solutions fail to fundamentally eliminate the arcing problem caused by the opening and closing of mechanical contacts under current-carrying conditions, this utility model provides a hybrid arc-free switching switch structure for a bridge-arm type on-load tap changer. This structure forms a composite bridge-arm switch unit and a composite transition switch unit by connecting solid-state bypass branches composed of anti-parallel thyristors in parallel across each bridge-arm mechanical switch and each transition mechanical switch. Utilizing time-delay relays in the control circuit, upon receiving a gear-switching command, the first time-delay relay, with its shorter operating time, first activates the thyristors in each solid-state bypass branch, transferring the load current to the solid-state bypass branch before the mechanical contacts actuate. Subsequently, the second time-delay relay, with its longer operating time, delays the driving mechanism of the corresponding mechanical switch. This ensures that all mechanical contacts complete opening or closing under zero-current conditions, fundamentally eliminating switching arcs, preventing contact erosion, and significantly extending the service life of the mechanical switches. Meanwhile, the thyristors in the solid-state bypass branch automatically turn off after the mechanical contacts have completed their opening and closing and the current has naturally transferred, as the current drops below the holding current. No additional turn-off circuit is required, meaning the solid-state bypass branch only conducts briefly during the switching transition. During steady-state operation of the voltage regulator, the load current is entirely borne by the mechanical contacts, without introducing additional conduction losses or heat dissipation burden. This combines the advantages of low loss in mechanical switches and arc-free switching in solid-state switches. Furthermore, this structure does not require altering the topology of the existing bridge-arm on-load tap changer; the solid-state bypass branch can be directly connected in parallel across each existing mechanical switch, and a control circuit can be configured. This results in good compatibility and low engineering implementation difficulty.

[0039] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the protection scope of the present invention.

Claims

1. A hybrid arc-free switching switch structure for a bridge-arm type on-load tap changer, characterized in that, The bridge arm type on-load tap changer includes a multi-tap tap changing winding (1), a bridge arm input common node (2), an upper output bus (3a), and a lower output bus (3b); The hybrid arc-free switching structure includes: multiple composite bridge arm switching units and multiple composite transition switching units; Some of the composite bridge arm switch units are electrically connected between the taps of the multi-tap voltage regulating winding (1) and the upper output bus (3a), while the remaining composite bridge arm switch units are electrically connected between the taps of the multi-tap voltage regulating winding (1) and the lower output bus (3b). Each composite bridge arm switch unit includes a bridge arm mechanical switch and a first solid-state bypass branch connected in parallel with it. The bridge arm mechanical switch is used to turn on or off during voltage regulation to connect different tap potentials to the upper output bus (3a) or the lower output bus (3b). The first solid-state bypass branch is used to turn on before the bridge arm mechanical switch is activated to achieve arc-free switching. Some of the composite transition switch units are electrically connected between the bridge arm input common node (2) and the upper output bus (3a), while the remaining composite transition switch units are electrically connected between the bridge arm input common node (2) and the lower output bus (3b). Each composite transition switch unit includes a transition mechanical switch and a second solid-state bypass branch connected in parallel with it. The transition mechanical switch is used to turn on or off during the voltage regulation gear switching process to provide a temporary closed current path. The second solid-state bypass branch is used to turn on before the transition mechanical switch is activated to achieve arc-free switching.

2. The hybrid arc-free switching switch structure of the bridge-arm type on-load tap changer according to claim 1, characterized in that, The plurality of composite bridge arm switch units include a first upper bridge arm switch T1, a second upper bridge arm switch T2, a third upper bridge arm switch T3, a first lower bridge arm switch T4, a second lower bridge arm switch T5, and a third lower bridge arm switch T6; each bridge arm switch corresponds to a first solid-state bypass branch; Among them, one end of the first upper bridge arm switch T1, one end of the second upper bridge arm switch T2 and one end of the third upper bridge arm switch T3 are respectively electrically connected to the corresponding taps of the multi-tap voltage regulating winding (1), and the other end is electrically connected to the upper output bus (3a). One end of the first lower bridge arm switch T4, one end of the second lower bridge arm switch T5, and one end of the third lower bridge arm switch T6 are respectively electrically connected to the corresponding taps of the multi-tap voltage regulating winding (1), and the other ends are all electrically connected to the lower output bus (3b).

3. The hybrid arc-free switching switch structure of the bridge-arm type on-load tap changer according to claim 2, characterized in that, Each first solid-state bypass branch includes a first thyristor (SCR-a) and a second thyristor (SCR-b); The anode of the first thyristor (SCR-a) is electrically connected to the cathode of the second thyristor (SCR-b) to form the first connection terminal of the first solid-state bypass branch; the cathode of the first thyristor (SCR-a) is electrically connected to the anode of the second thyristor (SCR-b) to form the second connection terminal of the first solid-state bypass branch. The first connection terminal of the first solid-state bypass branch is electrically connected to the terminal of the corresponding bridge arm mechanical switch near the tap of the multi-tap voltage regulating winding (1), and the second connection terminal of the first solid-state bypass branch is electrically connected to the terminal of the corresponding bridge arm mechanical switch near the upper output bus (3a) or the lower output bus (3b), thereby making the first solid-state bypass branch and the corresponding bridge arm mechanical switch connected in parallel.

4. The hybrid arc-free switching switch structure of the bridge-arm type on-load tap changer according to claim 2, characterized in that, The plurality of composite transition switch units include a first transition mechanical switch K1 and a second transition mechanical switch K2; The first transition mechanical switch K1 is electrically connected between the bridge arm input common node (2) and the upper output bus (3a), and the second transition mechanical switch K2 is electrically connected between the bridge arm input common node (2) and the lower output bus (3b); each transition mechanical switch corresponds to a second solid-state bypass branch.

5. The hybrid arc-free switching switch structure of the bridge-arm type on-load tap changer according to claim 4, characterized in that, Each second solid-state bypass branch includes a third thyristor and a fourth thyristor; The anode of the third thyristor is electrically connected to the cathode of the fourth thyristor, forming the first connection terminal of the second solid-state bypass branch; the cathode of the third thyristor is electrically connected to the anode of the fourth thyristor, forming the second connection terminal of the second solid-state bypass branch. The first connection terminal of the second solid-state bypass branch is electrically connected to the terminal of the corresponding transition mechanical switch near the bridge arm input common node (2), and the second connection terminal of the second solid-state bypass branch is electrically connected to the terminal of the corresponding transition mechanical switch near the upper output bus (3a) or the lower output bus (3b), thereby making the second solid-state bypass branch and the transition mechanical switch connected in parallel.

6. The hybrid arc-free switching switch structure of the bridge-arm type on-load tap changer according to claim 3 or 5, characterized in that, Each thyristor has the same structure; they are all silicon controlled rectifiers, with an anode, a cathode, and a gate. The silicon-controlled rectifier is configured such that: the rated voltage is not less than twice the voltage step size between adjacent taps in the multi-tap regulating winding (1); the rated current is not less than 1.5 times the rated load current of the bridge arm type on-load tap changer; and it automatically turns off when the current flowing through the silicon-controlled rectifier drops below the holding current.

7. The hybrid arc-free switching switch structure of the bridge-arm type on-load tap changer according to claim 6, characterized in that, The hybrid arc-free switching structure also includes a control circuit (4); The control circuit (4) includes: The switching command input terminal is connected to the signal control terminal of an external voltage regulator controller and is used to receive the gear switching command from the voltage regulator controller. The drive power input terminal is used to connect to an external drive power supply; The first signal output terminal is electrically connected to the gate of each of the thyristors; The second signal output terminal is electrically connected to the drive mechanism of each bridge arm switch and the drive mechanism of each transition mechanical switch; The first time-delay relay has its coil connected to the switching command input terminal, and its normally open contact connected between the first signal output terminal and the drive power input terminal. The second time-delay relay has its coil connected to the switching command input terminal, and its normally open contact connected between the second signal output terminal and the drive power input terminal; the operating time of the first time-delay relay is shorter than the operating time of the second time-delay relay. When the switching command input terminal receives the gear switching command, the external drive power supply supplies power to the first signal output terminal via the normally open contact of the first time delay relay to trigger each solid-state bypass branch electrically connected to the first signal output terminal, and supplies power to the second signal output terminal via the normally open contact of the second time delay relay to trigger the drive mechanism of each mechanical switch electrically connected to the second signal output terminal.

8. The hybrid arc-free switching switch structure of the bridge-arm type on-load tap changer according to claim 1, characterized in that, A load (5) is connected in series between the upper output bus (3a) and the lower output bus (3b), forming the output terminal of the bridge arm type on-load tap changer.

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